morphology and physiology of abdominal projection interneurones in the locust with mechanosensory...

THE JOURNAL OF COMPARATIVE NEUROLOGY 366556-673 (1996)

Morphology and Physiology of Abdominal Projection Interneurones in the Locust

With Mechanosensory Inputs From Ovipositor Hair Receptors

ELENI KALOGIANNI Department of Zoology, University of Cambridge, Cambridge CB2 3EJ, England

ABSTRACT The anatomy and physiological properties of eight non-giant projection interneurones

which originate from the locust terminal abdominal ganglion and receive wind and tactile inputs from ovipositor hair receptors are described. Their cell bodies (diameter 25-40 pm) are clustered in the anterolateral region of the eighth abdominal neuromere, and their axons ascend through either the contralateral or the ipsilateral connective to more anterior abdominal ganglia. In contrast to the giant interneurones, they have small-diameter axons and are not sensitive to cercal hair wind inputs. According to their arborisation pattern within the terminal abdominal ganglion, the non-@ant projection interneurones can be divided into those with main central arborisations in the ventral neuropil ianterolateral interneurones 1-6, ALIN1-ALIN6) and those with arborisations in the dorsal neuropil (ALIN7 and ALIN8). Interneurones of the first type possess four to six secondary neurites, which form a dense dendritic field in the ventral neuropil, either contralaterally or ipsilaterally to their soma. Two interneurones have contralaterally ascending axons and main dendritic fields contralateral to their soma. Two interneurones have contralaterally ascending axons and ipsilateral main dendritic fields. One interneurone has an ipsilaterally ascending axon and an ipsilateral main dendritic field. The primary neurites of interneurones with contralateral axons transverse the ganglion through dorsal commissure I. Five interneurones have unilateral ventral dendritic fields. One interneurone posseses bilateral ventral branches. Some interneurones project only in the eighth abdominal neuromere, whereas others send branches posteriorly into the neuropil of the ninth abdominal neuromere. Interneurones of the second type send three to four secondary neurites to the dorsal neuropil of the eighth and ninth abdominal neuromeres. One interneurone has an ascending axon in the ipsilateral connective and the other in the contralateral connective. The axons of the projection interneurones pass through a lateral or dorsal tract to the seventh abdominal ganglion. Their axonal projections are sparse, remain ipsilateral to the axons, and are confined to the dorsomedial neuropil. ALIN1-ALIN7 are depolarised and spike in response to wind and direct mechanical deflection of trichoid sensilla on both left and right ovipositor valves. They respond with more spikes to stimulation of hairs on the ventral valve ipsilateral to their main dendritic field. ALIN8, in contrast, shows a delayed inhibitory/excitatory response. I W i WiIey-I,iss, Inc.

Indexing terms: insect, oviposition, grasshopper, Schistocerca gregaria

Insect sensory receptors encode in their signals different types of information about the environment which can modify the animal’s behaviour. Phasic sensory signals from exteroceptors can initiate a motor response to external, potentially threatening stimuli, and rhythmic signals from extero- and proprioceptors can influence the motor patterns which produce the rhythmic movements they monitor. Both types Of signa1s are distributed to ganglia by projection interneurones. They originate from

cerebral, thoracic, or abdominal ganglia and show a great diversity in their central morphology, which reflects the diversity of their roles in different insect behaviours, such as walking, flying, stridulating, and ventilating. Previously

Accepted May 8’ 19f)5. Address reprint requests to Dr. E. Kalogianni, c/o Prof. M. Burrows.

Department of zoo lo^^, University of Cambridge, Downing Street. Cam- bridge CB2 ~ E J , England.

1 1996 WILEY-LISS, INC.

ABDOMINAL PROJECTION INTERNEURONES 657

described projection interneurones of locusts which process different sensory modalities include a population of mecha- nosensitive interneurones (Laurent and Burrows, 19881, certain auditory projection interneurones (Romer and Mar- quart, 19841, and an abdominal interneurone, A411, which processes inputs from neck wind-sensitive hairs during flight (Pfluger, 1984; Burrows and Pfluger, 1992).

Projection interneurones originating from the terminal abdominal ganglion and ascending to the anterior ganglia are known in crickets (Kamper, 1984; Jacobs and Murphy, 19871, locusts (Boyan and Ball, 1989a; Boyan et al., 1989a1, and cockroaches (Dagan and Parnas, 1970; Westin et al., 1977; Ritzman and Pollack, 1981). They respond to different types of mechanical stimuli such as wind and sound applied to the cercal hair receptors (Westin et al., 1977; Kamper, 1984; Boyan and Ball, 1989a). Thirteen interneurones in crickets (Edwards and Palka, 1974; Bacon and Murphey, 1984; Kamper, 1984), seven interneurones in cockroaches (Dagan and Parnas, 1970; Hamon et al., 19941, and ten interneurones in locusts (Boyan and Ball, 1989a; Boyan et al., 1989a,b) have been described which originate from the terminal abdominal ganglion, have contralaterally ascending axons, and possess central projections which can be associated with the cercal afferents projections in the neuropil of the terminal abdominal ganglion. In locusts, they can be divided into giant and non-giant interneurones, according to the diameter of their axons and cell bodies (Boyan et al., 198913). Cercal wind-sensitive hairs form monosynaptic connections with the giant interneurones (Boyan and Ball, 1989a) and polysynaptic connections with non-giant projection interneurones (Boyan et al., 1989a). The latter are thought to form a pathway of cercal input processing to the thoracic ganglia, in parallel with the giant interneurones, which are involved in the avoidance response evoked by cercal hair stimulation in locusts and cockroaches (Ritzmann and Pollack, 1981; Ritzmann et al., 1982; Boyan and Ball, 1989b).

In female locusts, however, there exists a sensory system, the ovipositor hair receptor system, which can also evoke an avoidance response of the animal to external mechanical stimuli and possibly involves projection interneurones. There are three types of hair mechanoreceptors on the ovipositor: long filliform hairs which are both wind and touch sensitive (Kalogianni, 19951, short tactile hairs, and short basiconic hairs which have both a mechanosensory and chemosensory function. Wind or direct mechanical displacement of the mechanosensory hairs evokes the with- drawal of the ovipositor from the source of stimulation, by exciting groups of ovipositor motor neurones located in different segmental ganglia (E. Kalogianni, in preparation). In addition, signals from these receptors are believed to be vital for the maintenance of the oviposition digging rhythm in locusts (Belanger and Orchard, 1992). Rhythmic excitation of the ovipositor hairs, which simulates their stimulation during oviposition digging, reveals their very low adaptation rates (Kalogianni, 1995) which implies that they could provide the CNS with rhythmic feedback during oviposition and thus influence the rhythmic motor pattern generating this behaviour. This pattern is produced by neurones in the terminal and the seventh abdominal ganglia (Thompson, 1986a,b), which are probably coordinated by projection interneurones. It appears that signals from the ovipositor receptors can influence the behaviour of both ovipositing and non-ovipositing locusts and that the inter- ganglionic processing of these signals involves projection

interneurones. Such cellular pathways of ovipositor signal processing, however, are unknown.

The aim of this study was to identify morphologically projection interneurones of the terminal ganglion which respond to ovipositor hair stimulation and could thus be postsynaptic to the ovipositor afferents. These interneurones are so far not identified, since the previously identified locust projection interneurones (Boyan et al., 1989a) do not branch in the neuropilar areas of the terminal ganglion where the ovipositor mechanosensory afferents project (Kalogianni and Burrows, 1996). The identification of ovipositor hair-sensitive interneurones would be a pre- requisite for the study of intersegmental integration of ovipositor sensory inputs and of their role in shaping the behaviour of ovipositing and non-ovipositing locusts.

I describe the morphology and physiology of eight non- giant interneurones in the terminal abdominal ganglion which respond to ovipositor hair excitation. The central projections and axons of these interneurones, which were identified as individuals, are in known tracts, commissures, and neuropilar areas of the terminal abdominal ganglion. The receptive fields of these interneurones on the ovipositor are mostly excitatory. The role of the projection interneurones in processing ovipositor inputs is discussed.

MATERIALS AND METHODS Adult female locusts Schistocerca gregaria (Forska)

were taken from our crowded colony in Cambridge.

Dissection Following removal of the wings and hind legs, the animal

was immobilized ventral side uppermost, and a longitudinal incision was made through the cuticle of the last abdominal segments to expose the genital ganglia (seventh and terminal abdominal ganglia). The oviducts were cut at their distal attachment site and fixed with pins at the anterior end of the abdominal cavity. The gut was stretched anteriorly and flattened with pins to avoid interference with the wax-covered stainless steel platform, on which the terminal abdominal ganglion was mounted. The ovipositor apodemes were immobilized, and all peripheral nerves, except the branches containing the ovipositor afferents (Kalogianni, in preparation), were severed. The abdomen was constantly superperfused with locust saline.

Recording and staining There are two types of hair receptors at the lateral areas

of the ovipositor: long filliform hairs which are both wind and touch sensitive (Kalogianni, 1995) and the less numerous short basiconic hairs which are touch sensitive (Kalo- gianni and Burrows, 1996). Two types of stimuli (wind and tactile) were delivered to the receptors of these areas. For a general survey of the responsiveness of different interneurones to deflection of ovipositor hairs, wind pulses of uncontrolled velocity and strength were delivered through a micropipette (tip diameter 0.8 mm). This stimulus was sufficient to deflect only the wind-sensitive hairs on one side of the ovipositor. All other hair receptors, e.g., cercal and abdominal hairs, were immobilised with vaseline.

For a more localised stimulation of ovipositor hairs, touch stimuli were applied with a fine paintbrush (diameter

658 E. KALOGIANNI

0.6 mm). This permitted the deflection of hairs on a single ovipositor valve exclusively, and thus it was possible to compare the responses of an interneurone to stimulation of hairs on the different valves. Each stimulus was repeated 3-5 times for each valve, with similar effects.

Insets to the figures represent in their shading quantita- tive differences in the responses of an interneurone to stimulation of hairs on the different valves. Dark shading represents the maximum response of an interneurone (i.e., mean number of spikes), and light shading represents < 60% of the maximum response.

The spikes of projection interneurones, evoked by stimulation of the ovipositor hair sensilla, were recorded extracel- lularly with silver hook electrodes placed under the anterior connectives of the seventh abdominal ganglion. For intracellular recordings, the terminal ganglion was bathed for 10 seconds in a 1% solution of protease (Sigma type XIV), prior to impaling the cell bodies of interneurones with glass microelectrodes filled with 6% cobalt hexammine chloride (resistance 100-200 MOhm). Following physiological char- acterization, interneurones were intracellularly stained by iontophoresing cobalt using 500-ms depolarising pulses with an amplitude of 5-10 nA for 15-20 minutes at 1 Hz. Preparations were left under a constant flow of saline for 1 hour to allow the dye to diffuse into the arborizations of the cell within the terminal abdominal ganglion. To stain the axonal projections of the interneurones into the seventh abdominal ganglion, it was necessary to use a 40-minute current injection period followed by 2 hours incubation under saline flow. The genital ganglia (seventh and terminal abdominal ganglia) were then removed from the animal, the cobalt was precipitated with ammonium sulphide (Pit- man et al., 19721, and the ganglia were fixed in 5% formaldehyde solution for 15 minutes. They were silver intensified (Bacon and Altman, 1977), dehydrated, and cleared in methyl salicylate. Selected preparations were photographed from whole mounts and drawn using a camera lucida. The data presented here are based on results from 80 animals, with each interneurone stained success- fully 2-4 times.

To reveal the clusters of cell bodies of the projection interneurones in the terminal abdominal ganglion, the cut ends of the anterior connectives of the seventh abdominal ganglion were placed in vaseline wells containing 6% cobalt hexammine chloride, and then the animals were incubated at 4°C for 36-48 hours. The backfills were developed according to the procedure described above for intracellular stains.

Intracellularly stained preparations were ultimately em- bedded in wax, and transverse serial sections (12-15 pm) of the terminal abdominal ganglion were cut. Drawings of groups of adjacent sections at different levels of the ganglion were combined. The nomenclature used to describe the tracts and commissures of the terminal abdominal ganglion is after Watson and Pfluger (1987).

RESULTS Projection interneurones of the terminal

abdominal ganglion The locust terminal abdominal ganglion (TAG) consists

of four abdominal neuromeres (eighth to l l t h neuromeres). To locate the cell bodies of the projection interneurones, originating from these neuromeres, unilateral backfills were made from a connective between the seventh and the

sixth abdominal ganglia (Connective A6-A7 in Fig. 1B). The backfills (n = 15) revealed nine to 14 cell bodies in the eighth abdominal neuromere (solid cell bodies in Fig. lAi,ii) and 13 cell bodies in the posterior (9th-11th) abdominal neuromeres (unfilled cells in Fig. 1A). They were classified as giant and non-giant ascending interneurones on the basis of the diameter of their axons and cell bodies (Boyan et al., 1989b). All projection interneurones of the 8th abdominal neuromere (filled cells in Fig. lAi,ii) were non- giant interneurones, of which seven to ten neurones had contralaterally ascending axons and two to four neurones had ipsilaterally ascending axons. Their somata, clustered a t the anterolateral area of the ganglion (anterolateral interneurones, ALINs in Fig. 1A) were located ventrally or laterally, near the origm of the eighth tergal nerve (Stgn, Fig. 1A). There were nine non-giant projection interneurones and four giant interneurones in the posterior (ninth to 11th) abdominal neuromeres (Fig. 1A). The majority of the posterior non-gant interneurones were arranged in two contralateral clusters in the ninth to l l t h abdominal neuromeres (unfilled cells, marked with arrows in Fig. l A d , and are thought to be the segmental homologues of the cluster of ALINs in the 8th abdominal neuromere (Boyan et al., 198913). The first posterior cluster of ascending interneurones was located posteriorly to the origin of the eighth sternal nerve (8stn) in the 9th neuromere and consisted of four dorsal non-giant neurones. The second posterior cluster consisted of three to five dorsal somata located near the root of the ninth segmental nerve (Fig. 1A). Individual posterior non-giant neurones, with ipsilateral cell bodies were also stained. Finally, giant interneurones 2, 3, and 4 (GINS, GINS, and GIN4 in Fig. 1A) were located ventrally near the midline of the ganglion, whereas the cell body of GIN1 was located dorsally, intermingled with the cells of the first posterior cluster. All g a n t interneurones ascended through the contralateral connective to the anterior ganglia.

Responses of projection interneurones to stimulation of the ovipositor trichoid sensilla During wind (Fig. 1D) or tactile (Fig. 1E) stimulation of

groups of ovipositor hairs, bursts of action potentials were recorded from the connective between the sixth and seventh abdominal ganglia (Fig. 1B-E). Intracellular recordings from the cell bodies of the anterolateral interneurones (ALINl-ALIN7) in the terminal abdominal ganglion showed that they responded to wind and mechanical deflection of the long filiform hairs on both the right and left ovipositor valves with depolarisation and spiking (Fig. 1D,E). Each soma spike of an anterolateral projection interneurone was followed by an action potential recorded from the anterior connective of the seventh abdominal ganglion (Fig. 1'2). No consistent responses to ovipositor hair stimulation were recorded from the more posterior non-giant interneurones. Giant interneurones 1-3 were also excited in response to ovipositor hair stimulation (Kalogianni and Burrows, 1996).

Morphology of the anterolateral projection interneurones

From the nine to 14 interneurones stained in the eighth abdominal neuromere, eight bilaterally paired ascending interneurones (ALIN1-ALIN8) were identified. which re-


4mV (C)

lOms (C) 50ms (D,E)

Fig. 1. Ai,ii: Drawings from whole mounts of the terminal abdominal ganglion 1 TAG) showing the distribution of the somata of projection interneurones that were stained when the connective anterior to the seventh abdominal ganglion (A7J was backfilled (see also BJ. Two clusters of cell bodies, one with contralateral axons and one with ipsilateral axons were stained in the eighth abdominal neuromere i filled cell bodies). Two clusters of contralateral cell bodies (unfilled cells, marked with arrows), some ipsilateral cells (unmarked unfilled cells,, and the four contralateral giant interneurones (GIN1, GIN2, GIN3. and GIN41 were stained in the posterior (ninth to 11th) abdominal neuromeres. Eight interneurones with anterolateral somata (ALINsi have receptive fields on the locust ovipositor. B: Simultaneous

intracellular recordings from the cell bodies of the anterolateral interneurones in the terminal abdominal ganglion (ALIN J and extracel- Mar recordings from the anterior connectives of the seventh abdominal ganglion (connective A6-A7) were obtained during wind or tactile stimulation of the trichoid sensilla on the locust ovipositor (wind; tactile). C: Superimposed sweeps trlggered by the soma spikes of an projection interncurone IALINZ 1 revealed a 1: 1 correlation with axon spikes recorded from the anterior connective. D,E: Individual anterolat- era1 interneurones responded with depolarisation and spiking to wind ID) and tactile iEJ stimulation (arrows) of the ovipositor trichoid sensilla. sn, secondary neurites; tgn, tergal nerves, s tn , sternal nerve.

660 E. KALOGIANNI

I l s n

Fig. 2. 'The morphology ofALIN1. Its soma lies ventrally a t the level of the origin of the eighth tergal nerve, and its branches originate from five secondary neurites (snl-sn5), extendingin the contralateral halfof the neuropil. Its axon ascends to the seventh abdominal ganglion (A71

sponded to ovipositor hair stimulation. Other types of stimuli, i.e., to abdominal and cercal hair receptors, failed to evoke a consistent response in these interneurones, which were morphologically characterized by intracellular cobalt staining. According to their gross arborisation patterns in the terminal abdominal ganglion, they could be classified as interneurones that mainly project to the ventral neuropil of the eighth abdominal neuromere (ALIN1-ALING) and interneurones with sparse but very extensive bilateral

where it gives rise to sparse projections in the dorsal neuropil. Its axonal branches remain ipsilateral. The axon then ascends a t least to the sixth abdominal ganglion. pn, primary neurite.

arborisations in the dorsal regions of the eighth and ninth abdominal neuropils (ALIN7 and ALIN8).

Anterolateral projection interneurones with ventral dendritic arborisations

Six projection interneurones with ventral branching in the eighth abdominal neuromere were identified as individuals according to the position of their soma, the course of

ABDOMINAL PROJECTION INTERNELJRONES 66 1

axon A

8tgn

8tgn

TAG

B

/sn5 AG

sh3 c

TAG

Fig. 3. A-F: Transverse sections of ALIN1, at levels indicated in Figure 2. Its main branching occupies the contralateral and midline areas of the ventral association center WAC) (stippled areas) of the eighth abdominal neuromere (B,C). Dense branching also occurs in the lateral neuropil between the VAC and the dorsal intermediate area (DIT) and dorsal median tract (DMT) tracts (B,C). Some branches cross the midline and ramify within the ventral and intermediate VAC (D,E).

Few branches project posteriorly within the contralateral VAC (F). Its primary neurite crosses the midline through Dorsal commissure I (DCI) and its axon exits the ganglion through DMT (A,B). Drawings are composites of a number of adjacent sections: A-D of three sections; E,F of four sections. In this and subsequent figures the VAC areas are stippled. VMT, ventral median tract; VIT, ventral intermediate tract; VC, ventral commissure; LDT, lateral dorsal tract.

their axon, and their branching pattern within the terminal abdominal ganglion (ALIN1-ALIN6). ALINl and ALIN2 had axons and main dendritic fields contralateral to their soma. ALIN3, ALIN4, and ALIN5 had contralateral axons and ipsilateral main dendritic fields. Finally, ALING had an ipsilateral axon and ipsilateral main projections.

The soma of ALINl is 40 pm in diameter and lies ventrally, approximately 100 Fm from the origin of the eighth tergal nerve (Fig. 2). Its primary neurite (pn) runs contralaterally, along the dorsal bound- aries of the VAC of the eighth abdominal neuromere for 200 )*m sending fine ipsilateral branches near the midline (Figs. 2, 3D). It crosses to the contralateral neuropil via dorsal commissure I (DCI) and then gives rise to five contralateral secondary neurites (snl-sn51, which create a dense ventral dendritic field in the contralateral neuropil of the eighth abdominal neuromere (Figs. 2, 3B-D). Secondary neurites 1 and 2 project laterally and medioventrally, with their fine branches confined to the contralateral VAC (stippled area, Figs. 2, 3B). Secondary neurite 3 projects toward the ganglionic midline and gives rise to fine arborisations within the ventralmost region of VAC, some of which cross

Interneurone I (ALJNI).

the midline (Figs. 2,3D,E). Secondary neurites 4 and 5 run posteriorly and arborize in the contralateral VAC of the eigth and ninth neuromeres (Figs. 2, 3C-F). No ipsilateral arborisations were found at this level. The axon of ALINl passes into DMT and ascends to the 7th abdominal ganglion through the connective, contralateral to its soma (axon in Fig. 3A,B). Prolonged intracellular staining revealed the axonal projections of ALINl in the seventh abdominal ganglion (A7, Fig. 2), which arborise dorsally in the ipsilat- era1 neuropil of the ganglion before ascending to the sixth abdominal ganglion.

ALINl responds to tactile stimulation of the trichoid sensilla on both the ventral (Fig. 4A,C) and dorsal (Fig. 4B,D) ovipositor valves, both ipsilaterally and contralaterally, with depolarisation and superimposed spikes. Record- ings were obtained from both the left and right side ALINl homologues which consistently showed that ALINl responds with more spikes to inputs from the ventral valve, contralateral to its soma (Fig. 4A) but ipsilateral to its dendritic field (see inset of Fig. 4 for receptive fields: dark shading represents the maximum response, and light shading represents < 60% of the maximum response).

662 E. KALOGIANNI

A I PSI LATERAL

B

I TACTILE

A

Fig. 4. Physiological responses of ALINl to tactile stimulation of the ovipositor trichoid sensilla. Deflection of groups of hairs on the contralateral tA,B) and ipsilateral (C,D) valves (relative to its soma) evokes an excitatory response in the interneurone. The strongest response was evoked by stimulation of ventral valve hairs which are

tnterneurone 2 (ALJN2). In contrast to ALIN1, its ventral cell body lies more anteriorly, near the origin of the connectives (diameter 35 pm, Fig. 5A, Cl and its primary neurite runs posteriorly and then turns sharply toward the contralateral side (Fig. 5A). I t follows the dorsal boundary of the VAC (stippled area) of the eighth abdominal neuromere (pn in Fig. 5D), within the DCI, and gives rise to some fine projections in the dorsal area of the VAC near the midline (Fig. 5Dl. I t then produces a dense contralateral dendritic field, which originates from four secondary neurites (Fig. 5A). Secondary neurite 1 ( sn l ) originates anteriorly and ramifies within an area dorsal to the VAC (Fig. 5A,C), whereas secondary neurites 2 and 4 (sn2, sn4) occupy the contralateral VAC (Fig. 5A,C,D). Secondary neurite 3 (sn3) projects posteriorly and is confined to the

CONTRA IPS1

vv vv

contralateral to its soma Le., ipsilateral to its main dendritic field, dark shading in the inset represents maximum response). The responses to stimulation of the other three valves were weaker (light shading represents < 60% of the maximum response).

VAC (Fig. 5E-G). The axon of ALIN2 ascends to A7 through the contralateral DMT (Fig. 5B,Cl. The features that distinguish ALIN2 from ALINl are the following: First, its soma is located more anteriorly and closer to the midline than ALIN1. Second, its primary neurite runs posteriorly before turning contralaterally. Third, ALINl posesses a secondary branch (sn3), transversing the ganglion to reach from the contralateral to the ipsilateral neuropil, which is lacking in ALINB. Fourth, during the course of an experiment recordings were susequently obtained with cobalt electrodes from both cells. Rather invol- untarily, both cells were partly stained and were visible in the same preparation after silver intensification. Further- more, each neurone was stained in more than one animal with very little variation in its morphology, in particular in


A

axon

&

axon

C Bm sn4

Fig. 5. A: The morphology of ALIN2. The arborisations of ALINZ conform to the pattern described for ALIN1, with dense arborisations in the contralateral neuropil of the eighth abdominal neuromere originating from four secondary neurites (snl-sn4). Its soma has a characteristic position, lying below the origin of the connective. ALIN2 has a receptive field on the valves that are ipsilateral to its main dendritic field (see inset). B-G: Transverse serial sections of ALIN2, taken a t planes indicated in A. Its branches OCCUDY the ventral and

ventromedial neuropil of the eighth abdominal neuromere (C,D). Branches orib~nating from sn3 project posteriorly and reach the VAC of the ninth abdominal neuromere (E-G). The large profiles lying laterally in composite E represent somata of the ventral valve opener motor neurones. Its pn crosses the midline through DCI and its axon exits the ganglion through DMT (B,C). B,C and E-G are composites of two sections, D of three sections.

664 E. KALOGIAIVNI

axon

\ ,’ / 8stn /

Fig. 6. A: The morphology of 4LIN3. The dendritic field ofALIN3 is sparse and originates from seven fine secondary neurites (snl-sn7). They project in both the contralateral and ipsilateral halves of the eighth abdominal neuromere. Its axon exists the ganglion through the contralateral connective and enters the seventh abdominal ganglion. Its axonal branches originate anteriorly to the 7stn origin and ramify dursomcdially. They remain ipsilateral and bear varicosities B-E: I ransversc. sections of ALIN‘S, a t planes indicated in A. Its axon exlts ,,

regard to cell body position and central branches. Only stains that were judged to be complete were considered.

ALIN2 has an excitatory receptive field that spans all the ovipositor valves, but is most sensitive to tactile inputs from the valves contralateral to its soma (see inset of Fig. 5).

This interneurone is characterised by dendritic arborisations which are confined to the eighth abdominal neuromere (Fig. 6A). Its cell body (diam-

Interneurone 3 (ALIM).

B

C

TAG

100ym axon

sn5

sn6 sn4 J /

8tgn

TAG

E

op. m.n.

TAG

the ganglion through DIT tB,C), and its branches occupy the border area of the VAC, being slightly more dense on the ipsilateral side tin relation to the soma). Its primary neurite transverses the ganglion through vDCI. Note the presence of bilateral ventral branching of ALINS a t the level of the origin of the 8th tergal nerve (8tgn in D). B is a composite offour sections, C of threc sections, D of six sections. and E of five sections.

eter 35 pm) is situated laterally at the edge of the ganglion, near the origin of the eighth tergal nerve. It possesses ipsilateral arborisations which originate from three fine secondary neurites (snl-sn3) and ramify into the VAC (stippled area, Fig. 6D). A fourth secondary neurite (sn4) ramifies anteriorly and ventrally to the VMT (Fig. 6D). Its axon passes through the DCI and then gives rise to sn5 which sends fine branches in the contralateral side between the DIT and the VAC (Fig. 6C). This interneurone can be

ABDOMINAL PRO.JECTION INTERNEURONES 665

I/ C O N T R A IPS1 IPSILATERAL

U L

I

Fig. 7. A-D: Physiological responses of ALIN3 to tactile stimulation of the ovipositor trichoid sensilla. ALIN3 has a main receptive field on the ventral valve that is ipsilateral to its main dendritic arborisations Receptive fields are shown in the inset.

distinguished from the other anterolateral interneurones by its ventral projections in both the ipsilateral and the contralateral regions of the VAC, at the level of the origin of 8tgn (Fig. 6D). These arise mainly from sn l , sn6, and sn7 (Fig. 6El. The axon ofALIN3 appears to pass into DIT (Fig. 6Cl and ascends through the contralateral connective (Fig. 5B) to the next anterior ganglion. It sends branches in the dorsal neuropil, anteriorly to the origin of the seventh sternal nerve (7stn, Fig. 6A). All axonal branches arborise ipsilaterally to the axon and bear varicosities (arrows, Fig. 13A).

ALIN3 is most sensitive to inputs from the ventral ovipositor valve that is ipsilateral to its soma (and to its dendritic field, see heavily stippled valve of the inset in Fig. 7).

Interneurone 4 (ALIN4) The cell body of ALIN4 (diameter 25 km) is located

laterally, and its primary neurite (pn) runs posteriorly and dorsally for 30 pm before turning 90" to project contralaterally (Fig. 8A). Approximately 150 km from the cell body it gwes rise to three secondary neurites (snl-sn3), which project ipsilaterally (Fig. 8A). Secondary neurite 1 projects into the anterior region of the eighth abdominal neuromere, whereas secondary neurites 2 and 3 project posteriorly and create a dense ipsilateral dendritic field in a medioventral plane (Figs. 8A,C,D, 13B). Upon crossing the ganglionic midline via DCI, the primary neurite gives rise to three more secondary neurites (sn4-sn6) which create a contralateral field confined to the anterior half of the eighth abdominal neuromere (Fig. 8A). Finally, sn7 ramifies posteriorly and dorsally (Fig. 8A,F). The projections of sn3 reach the point of origm of the 8stn (Fig. 8F). The axon of ALIN4 ascends anteriorly through DIT (Fig. 8C) and exits via the contralateral connective (Fig. 8B). The features that distinguish ALIN4 from ALIN3 are, first, the characteristic course of its primary neurite, and second, the greater density of the dendritic field of ALIN4 and the dorsal branches, which are lacking in ALIN3. More specifically,

sn7 of ALIN4 ramifies in the contralateral dorsal neuropil, whereas the secondary neurites, originating from the same area of ALIN3, project ventrally. The most pronounced difference, however, in morphology of ALIN3 and ALIN4 is in the extent of their posterior branching in the ganglion. The posterior projections of ALIN4 descend well beyond the level of the origin of the eighth sternal nerve (8stn), whereas the branches of ALIN3 terminate at a more anterior position.

ALIN4 has excitatory receptive fields on the ovipositor, mainly on the ventral valve ipsilateral to its main dendritic field (heavily stippled valve in the inset of Fig. 8).

Interneurone 5 (ALIN5) This interneurone (soma diameter 25 pm) possesses two

distinct dendritic fields in the 8th abdominal neuromere which extend also in the ninth to 11th neuromere, one in the ipsilateral and one in the contralateral neuropil (Fig. 9A). Its primary neurite runs contralaterally for approximately 75 km before giving rise to six secondary neurites (snl-sn6) whose dense fine branches invade both the ventral and dorsal areas of the ipsilateral neuropil of the eighth and ninth abdominal neuromeres (Fig. 9A,C-H). Secondary neurites 1-4 run posteriorly (Fig. 9A): s n l and sn2 project medioventrally with branches entering the VAC (Fig. 9E); sn3 and sn4 project more dorsally. Finally, sn5 and sn6 arborize anteriorly (Fig. 9A,C).

The primary neurite then continues into DCI to the contralateral neuropil (Fig. 9F) where it gives rise to an area of sparse but extensive fine branches (Fig. 9D-H). This dendritic field origmates mainly from a single axonal branch (ax.b.) which gwes rise to numerous dorsal branches with varicose endings (Figs. 9A, 13C). The axon of ALIN5 passes probably through DIT to the next anterior ganglion (Fig. 9B,C).

ALIN5 receives excitatory inputs from the ventral ovipositor valve, ipsilateral to its main dendritic arborisations (heavily stippled valve in inset of Fig. 9A).

666 E. KALOGIANNI

Fig. 8. A The morphology of ALIN4, drawn from whole mounts. ALIN4 has a main dendritic field within the ipsilateral neuropil, originating from snl-3 and a more sparse contralateral field formed by the fine branches of sn4-6. Sn4 and sn6 originate from the median part of the primary neurite and send projections into the median area, thus providing continuity between the ipsilateral and contralateral fields. Posterior projections originate ipsilaterally from sn3 and contralaterally from sn7. B-F: Transverse sections of ALIN4, at planes indicated

in A. Its axon exits the ganglion through the contralateral DIT (R). and its branches at the level of the 8tgn origin are slightly more dense in the ipsilateral area of'the VAC ( C ) Arborisations also extend dorsally into the VAC, in the area defined by LDT and the DCIII (D). More posterior branches project into the dorsal area of the VAC (E) , but only the ipsilateral branches reach the ninth abdominal neuropil (F) . B,D, and E are composites of three sections, C of four sections, and F of two sections.


Fig. 9 A: The morphology of ALINS ALINB is characterized by two extensive fields in the ipsilateral and contralateral neuropiles, which are distinct since no branches occur near the midline. The ipsilateral dendritic field, originating from s n l to sn6, is dense and extends posteriorly well into the ninth abdominal neuromcre. The contralatcral field, orignating from a single axonal branch (ax.b. ), is equally large but with very sparse varicose branches. ALIN5 has excitatory receptive fields on the ovipositor, with strongest response evoked by stiinulation of hairs on the ventral valve, ipsilateral to its soma (see inset]. B-H:

Interneurone 6 (ALIN6) This interneurone has a ventral cell body (diameter 30

pm), and a n ipsilaterally ascending axon (Fig. 10A). I ts central branching originates from five secondary neurites. S n l projects laterally, and sn2 and sn5 send send branches into the VAC of the ipsilateral neuropil (Fig. 10B,D). Sn3 and sn4 project across the midline of the ganglion, following the ventral boundary of the neuropil, and ramify within the ventralmost area of'the VAC, both ipsilaterally and contralaterally (Fig. IOD). Its axon ascends through the VLT to the ipsilateral connective (Fig. 10B). ALING is excited by wind and mechanical stimulation of ovipositor hairs ipsilat- era1 to its soma and main dendritic field (see inset of Fig. 10A).

Anterolateral projection interneurones with dorsal dendritic arborisations

Two interneurones with extensive branching in the dorsal neuropil of the terminal abdominal ganglion that respond to ovipositor hair stimulation were morphologically identified (ALIN7 and ALIN8).

Transverse sections of ALIN 5, at levels indicated in A. Its pn crosses the midline via DCI iF), and its axon passes through DI'Y and ascends in the contralateral connective (Bl. It has prominent projections within the dorsomedial ncuropil of the eighth abdominal neuroniere on both sides of the ganglion tC,Dl. A few branches enter the lateral area of the ipsilateral VAC ID.E), whereas the contralateral projections remain dorsal IE,FI Ipstlateral branches project posteriorly in the lateral area of the neuropile, cxtending both ventrally and dorsally tG,H,. B-D are composites of two adjacent sections, E-G of' three sections

Interneurone 7 (AlJN7) . ALIN7 has a lateral soma (30 Fm) and an ipsilaterally ascending axon (Fig. 11AJ. Three secondary neurites isnl-sn3) send their branches to invade the ipsilateral i sn l and sn2) and contralateral area of the dorsal neuropil (sn2 and sn3) of the terminal abdominal ganglion (Fig. 11A). Its axon ascends via LDT to the seventh abdominal ganglion. ALIN7 is most sensitive to stimulation of the ovipositor trichoid sensilla, ipsilateral to its soma (Fig. l l B and inset).

Interneurone 8 (ALIIW). ALIN8 has a ventral soma (diameter 25 pmi, and its axon ascends through the contralateral connective (Fig. 12A). I ts primary neurite crosses the midline through DCI (pn, Fig. 12CJ and ascends through LDT to the next anterior ganglion (Fig. 12Bi. I ts dendritic projections originate from four secondary neurites (snl-sn4, Fig. 12A-D) and are confined in the dorsal neuropil (snl-sn4, Fig. 12A-D) S n l and sn2 send branches into the ipsilateral neuropil, sn3 into the medial area, and sn4 into the contralateral neuropil (Fig. 12A). ALIN8 is the only anterolateral interneurone which is inhibited in response to ovipositor hair stimulation (Fig. 12E).

668 E. KALOGIANNI

ALING

sn2 n

Fig. 10. A Morphology of ALING. ALING has an ipsilaterally ascending axon, and its arborisations occupy mainly the ipsilateral and median neuropil of the eighth abdominal neuromere. Many branches cross the midline. They origmate from five secondary neurites (snl- sn5) Inset shows the receptive fields of ALING on the ovipositor, with stimulation of the ventral valve, ipsilateral to its soma evoking the strongest response. B-D: Transverse sections of ALING. a t levels

indicated in A. Most of its branches ramify ipsilaterally in the ventral neuropil and reach as far dorsally as the level of DIT (B). Some branches enter the ipsilateral VAC (0, and a large number of branches extend into the ventralmost neuropil, crossing the midline (D). Its axon ascends through VLT. B and D are composites of five sections, C of four sections.

Table 1 summarizes the morphological features and main receptive fields on the ovipositor of the non-giant projection interneurones with mechanosensory inputs from the ovipositor hair receptors.

DISCUSSION Morphology of the anterolateral

projection interneurones This report describes the morphology of eight non-giant

projection interneurones with cell bodies in the eighth abdominal neuromere of the locust terminal ganglion. In crickets, mantids, and locusts, projection interneurones occur in segmentally repeated clusters within the terminal abdominal ganglion, which comprises several neuromeres (for crickets, see Jacobs and Murphey, 1987; for locusts, see Boyan et al., 1989b; for mantids, see Boyan and Ball, 1986). In the locust, there are four giant ascending interneurones and three segmentally homologous clusters of non-giant interneurones, i.e., an anterolateral cluster in the eighth abdominal neuromere, which includes the eight interneurones identified here, and two lateral clusters in the poste-

rior (ninth to 11th) abdominal neuromeres (Boyan et al., 1989b).

Anterolateral projection interneurones 1-8 could be identified as individuals, on the basis of their soma position, primary neurite and axon paths, and central neuropilar projections, which were consistent for each individual interneurone in different animals. From the eight identified projection interneurones, six interneurones (ALIN1- ALING) have the following morphological features: First, their somata lie ventrally or laterally in the anterolateral cortex of the terminal abdominal ganglion, a t the level of the origin of the eighth tergal nerve. Second, the primary neurites of ALIN1-ALIN5, which have contralaterally ascending axons, all pass to the contralateral neuropil, dorsal to the ventral association centre (VAC) of the eighth abdominal neuromere, through DCI. Third, all interneurones have central branches which ramify within the VAC and the lateral neuropil of the 8th abdominal neuromere. Two interneurones have branches which are confined to the eighth abdominal neuromere (ALINS, ALING), whereas the remaining four interneurones (ALIN1, ALIN2, ALIN4, and ALIN5) have branches which enter the neuropil of the

A4BDOMINAL PROJECTION INTERNEURONES 669

1 . / I /

WIND 200ms

Fig. 11. A Morphology of ALIN7. ALIN7 is characterized by extensive contralateral and ipsilateral dendritic arborisations, which, in contrast to the other anterolateral interneurones, extend tu the dorsal neuropil. Its projections originate from three secondary neurites (snl-

sn3) with snl and sn2 ramifying in the ipsilateral, and sn3 in the contralateral neuropil. B: ALIN7 has excitatory receptive fields on the ovipositor (see inset 1.

posterior (ninth to 11th) neuromeres. Fourth, their axons pass through either a lateral or dorsal tract to the seventh abdominal ganglion (ALIN1 and ALINB pass through DMT; ALINS, ALIN4, and ALIN5 pass through DIT; and ALING passes through LVT). Fifth, the majority of their secondary branches extend either contralaterally or ipsilaterally to their soma. A population of projection interneurones, similar to ALIN1-ALING, with anterolateral cell bodies, contralateral or ipsilateral axons, and main projections in either the contralateral or ipsilateral neuropil have been described in the locust metathoracic ganglion. They receive mechanosensory inputs from leg receptors (Laurent and Burrows, 1988).

The remaining two identified projection interneurones (ALIN7 and ALIN8) have similar soma position, exit the ganglion via LDT, and their central arborisations (in contrast to ALIN1-ALING) invade the dorsal neuropil of all the

neuromeres of the terminal abdominal ganglion. Further- more, their projections do not appear to predominate in either the contralateral or ipsilateral neuropil.

In the locust terminal ganglion, the morphology of six non-giant projection interneurones and four giant interneurones, which respond to wind stimulation of the cercal hair receptors, have previously been described (Boyan et al., 1989a). The giant interneurones have contralateral axons and ascend mostly through different tracts to ALIN 1-6: GIN2, GIN3, GIN4 pass through LDT, and GIN1 passes through VIT. The somata of five previously described non-@ant interneurones are located in the posterior abdominal neuromeres. The sixth identified non-giant interneurone has its cell body in the eighth abdominal neuromere (cell 7, Boyan et al., 1989a) and probably belongs to the ALINs which do not respond to ovipositor hair deflection. Like the rest of the previously identified interneurones, the

670 E. KALOGIANNI

Fig. 12. ALINR posseses arborisations which originate from four secondary neurites (snl-sn4). The ipsilateral dendritic field of ALINR. originating from secondary neurites 1-3, is more dense than the contralateral field originating from sn3 and sn4 Its projections are

confined in the dorsal neuropil (B-D). Its pn crosses the ganglion through DCI and exits via LDT. E: ALINS shows a delayed excitatory/ inhibitory response to tactile stimulation of the ovipositor tricoid sensilla.

projections of cell 7 are confined in the posterior (ninth to 11th) abdominal neuromeres. Five of the cercal hair- sensitive interneurones have contralateral axons, and one has an ipsilaterally ascending axon (cell 17 of Boyan et al., 1989a) and, thus, resembles the two ipsilaterally ascending interneurones of the anterolateral interneurone group described here (ALING, ALIN7). Cell 17, however, has its soma and dendritic arborisations in the posterior abdominal neuromeres, whereas ALING and ALIN7 have their somata in the eighth abdominal neuromere and therefore appear to belong to the same cluster as the contralaterally ascending ALINs.

Anterior projections of anterolateral projection interneurones

Anterolateral projection interneurones ascend through the connectives and arborise within the seventh abdominal

ganglion before continuing their course to the sixth abdominal ganglion. They ascend anteriorly at least to the metathoracic ganglion, because their potentials can be recorded from the posterior connectives of this ganglion. Their axonal projections are characterised by varicose endings, which contrasts with the bulk of their projections arising from their secondary neurites which are smooth and have a spiny appearance. Similar varicosities characterise the axonal projections of locust mesothoracic projection interneurones (Laurent, 1987) and some central branches of spiking local interneurones (Burrows and Siegler, 1984) which are predominantly output synaptic sites (Watson and Burrows, 1985). ALINs also possess varicose branches within the terminal abdominal ganglion, which, for ALIN5, are spa- tially separated from the presumed input synaptic areas he. , the contralateral projections are dorsal and bear varicosities, whereas the ipsilateral branches are ventral

ABDOMINAL PROJECTION IKTERNEURONES 671

Fig. 13. .dicrophotographs of ALIN3, ALIN4, ALIN5, taken from whole mounts. A: Axonal projections of ALIX3 in the seventh abdominal ganglion, a t a dorsal plane, with varicosities (arrows). B: Morphol- n m nf t h o v p n t r n m d i n l nrhnrisntinns nf AT.lY4 in thP tprminnl o m in R 34 tlm in C

abdominal ganglion. C: Contralateral projections of ALIS5 in the terminal abdominal ganglion originating from a single axonal branch (unmarked arrow) with varicose endings. Scale bar = 72 l m in A. 100

672 E. KALOGIANNI

TABLE 1. Morphological Features and Main Receptive Fields of the Anterolateral Projection Interneurons with Mechanosensory Inputs from Ovipositor Hair Receptors

Interneurone Soma ( u m ) Axon Tract Commisure Main neurites Main receutive field

AI. lS1 40 Contralateral DMI' ALINZ 35 Contralateral DMT AI.IN3 35 Contralateral DI'S .%IN4 25 Contralateral DIT ALlNR 25 Contralateral DI'T AI.IN6 YO Ipsilateral VL'I' Al.IN7 30 IpSlkiterdl Lwr ALlNH 30 Contralateral LD'S

DCI Contralateral !ventral DCI Contralateraliventral DCI Bilateral ,ventral DCI Ipsilaterallventral lfCl lpsilaterd {ventral - Ipsilateraliventral - BikterdlidOrsal

1 x 1 Bilateral !dorsal

Excitatory 'contrdateral Excitatory 'contralateral Exatatorv Ipsilateral Excitatory ' ipsilatrral Excitatory, ipsilateral ExCiVdtoly ipsilateral Excitatory Ipsilateral Inhihitiirv excitatorv

and have a spiny appearance). A similar bilateral division of varicose and spiny projections was also described for some locust auditory projection interneurones in the metathoracic ganglion (Romer and Marquart, 1984) and a locust wind-sensitive projection interneurone in the terminal ganglion (cell 17, Boyan et al., 1989a).

Inputs to anterolateral projection interneurones

Ovipositor wind-sensitive hair receptors respond to wind and direct mechanical displacement with bursts of spikes, which reflect both the velocity and direction of the stimulus (Kalogianni, 1995). In the present study, seven non-giant projection interneurones (ALINlLALIN7) have excitatory receptive fields on both left and right ovipositor valves. Recordings obtained from both bilateral homologues of these interneurones revealed a correlation between their morphology and their receptive fields, since they respond with more spikes to deflection of the ovipositor trichoid sensilla on the ventral valve ipsilateral to their main dendritic field. The weaker response to the ipsilateral dorsal valve deflection could be due to the smaller number of hairs on the dorsal valves (Kalogianni and Burrows, 1996). The response, however, of ALIN3-7 was even weaker than it is for ALINl and ALIN2. In a subsequent study imposed mechanical deflection of controlled strength and velocity showed that ALINl and 2 respond with tonic spiking that greatly outlasts the stimulus, whereas ALIN3-7 respond phasically and only at the onset of stimulation. This would indicate additional indirect pathways to ALINl and 2 which could be responsible for overcoming the bias in the input signals, owing to the smaller number of dorsal hairs. Could, however, the morphology of the anterolateral interneurones give any indication of the mono- or polysynaptic nature of the pathways of ovipositor signal processing by these interneurones?

Mechanosensory afferents on the locust leg (Newland, 1991) and the locust cerci (Boyan et al., 198913) arborise within specific areas of the CNS. Hair afferents from both ventral and dorsal ovipositor valves in the locust arborise within the ventral neuropil of the eighth abdominal neuromere (Kalogianni and Burrows, 1996). They overlap unilat- erally with the central projections of ALIN1-6, which implies that ovipositor inputs from hairs ipsilateral to the dendritic field of the ALINs could be processed through a monosynatic pathway. In contrast, the excitatory effect on the interneurones of ovipositor hairs contralateral to the interneurones' main dendritic field should be exerted through at least one intermediate interneuronal layer. Similarly, the excitation of ALIN7, which is characterized by the lack of ventral branching in the eighth abdominal neuromere where the ovipositor afferents project, must involve a polysynaptic pathway. Finally, ALIN3 and, to a

lesser extent, ALIN4 have bilateral ventral branching in the eighth neuromere, so they could receive direct inputs from both ipsilateral and contralateral ovipositor valve hair receptors.

ALINS is the only anterolateral projection interneurone with mixed inhibitorylexcitatory receptive fields on the ovipositor. I t is unlikely that it receives direct ovipositor inputs since 1) their effects appear with a long delay and 2) there is no anatomical overlap between its central branches and the ovipositor afferent projections. Furthermore, there is no evidence for direct inhibitory pathways between mechanosensory afferents and their postsynaptic cells in invertebrates.

Role of anterolateral projection interneurones In locusts, crickets, and cockroaches, cercal afferent

signals are processed by giant projection interneurones originating from the terminal abdominal ganglion. Parallel pathways of cercal signal processing to the thoracic ganglia by non-giant interneurones have also been suggested in cockroaches (Dagan and Parnas, 1970) and locusts (Boyan et al., 1989a). The non-giant projection interneurones described in the present study are not likely to be primary integrators of cercal inputs because they are not sensitive to cercal hair deflection. They could, however, be involved in two other types of behaviour, namely the avoidance response evoked by ovipositor hair stimulation in non- ovipositing locusts and the rhythmic oviposition digging behaviour. The pathways underlying both behaviours involve neurones in several segmental ganglia to which ovipositor signals could be distributed by the anterolateral projection interneurones. The pattern of connections between the ovipositor afferents and the anterolateral interneurones, their output connections, and their precise role during oviposition are yet to be defined.

ACKNOWLEDGMENTS I thank M. Burrows, F. Kuenzi, T. Matheson, P. New-

land, and A. Norman for their comments on the manu- script. This work was supported by a Wellcome Trust grant to M. Burrows.

LITERATURE CITED Bacon, J.P., and J.S. Altman (1977) A silver intensification method for

cobalt-filled neurons in wholemount preparations. Brain Res. 138:359- 363.

Bacon, J.P., and B.K. Murphey (1984) Receptive fields of cricket giant interneurons are related to their dendritic structure. J. Physiol. (Lond). 352:601-623.

Belanger, J.H., and I. Orchard (1992) The role of sensory input on maintaining output from the loeust oviposition digging central pattern generator. J . Comp. Physiol. IAI 171r495-503.


Boyan. G.S. , and E.E. Ball 11986) Wind sensitive interneurons in the terminal ganglion of praying mantids. J. Comp. Physiol. IAI 159773- 789.

Boyan. GS. . and E.E. Ball (l989a) The wind-sensitive cercal receptorigiant interneurone system of the locust Lorusta rnzgratoria. 11. Physiology of giant interneurons. J. Comp. Physiol. IAl f65:511-521.

Boyan. G.S., and E.E. Ball 11989b) The wind-sensitive cercal receptorigiant interneurone system of the locust Locusta rnigratoria. 111. Activation of thoracic motor pathways. J . Comp. Physiol. IAl 165.523-537.

Bovdn. G.S., J.L.D. Williams. and E.E. Ball (1989a) The wind-sensitive cercal receptor!@ant interneurone system of the locust, Locusta rnigra- /orin. IV. The non-giant interneurones. J . Comp. Physiol. [A1 f65:539- 552.

Boyan, G.S., J.I,.D. Williams, and E.E. Ball (1989b) The wind-sensitive cercal receptorigiant interneurone system of the locust, Locusta rnigra- forla. I . Anatomy of the system. J . Comp. Physiol. [A] 165:495-510.

Burrows, M.. and H.J. Pfluger 11992) Output connections of a windsensitive interneurone with motor neurones innervating flight steering muscles in the locust. J. Comp. Physiol. IAl 171:437-446.

Burrows. M., and M.V.S. Siegler 11984) The morphological diversity and receptive fields of spiking local interneurones in the locust metathoracic ganglion. J Comp. Neurol. 224:483-508.

Dagan. D.. and I. Parnas (1970) Giant fibre and small fibre pathways involved in the evasive response of the cockroach Periplaneta americana. J. Exp. B i d .52:312-324.

Edwards, J.S., and J . Palka 11974) The cerci and abdominal giant fibres of the house cricket Acheta domesticus. I. Anatomy and physiology of normal adults. Proc. K. Soc. Lond. [Biol. 1185:83-103.

Hamon. A, . J.C. Guillet, and J .J . Callec (1994) Patterns of monosynaptic input to the giant interneurones 1-3 in the cercal system of the adult cockroach. J. Comp. Physiol. [A] 174:91-10".

Jacobs, G A . , and R.K. Murphey (1987) Segmental origins of the cricket giant interneuron system. J. Comp. Neurol. 265: 145-157.

Kalopanni. E. 19951 Physiological properties of wind-sensitive and tactile sensilla on the ovipositor and their role duringoviposition in the locust J . Exp. Biol. 198:1359-1369.

Kalogianni, E. and M. Burrows (1996) Parallel processing of mechanosensory inputs from the locust ovipositor by intersegmental and local interneurones. J. Comp. Physiol. [A] (in press).

Kamper, G. (1984) Abdominal ascending interneurons in crickets: Re- sponses to sound at the 30-Hz calling-song frequency. J . Comp. Physiol. I A I 155507-520.

Laurent, G. (19871 The morphology of a population of thoracic intersegmental interneurones in the locust. J. Comp. Neurol. 256r412-429.

Laurent, G., and M. Burrows 11988) A population ofascending intersegmental interneurones in the locust with mechanosensory inputs from the hind leg. J. Comp. Neurol. 275-12 .

Newland, P.L. 11991) Morphology and somatotopic organisation of the central prnjections of afferents from tactile hairs on the hind leg of the locust. J. Comp. Neurol. 912:493-508.

Pfluger, H.J. (1984) The large fourth abdominal intersegmental interneuron: a new type of wind sensitive ventral cord interneuron in locusts. J. Comp. Neurol. 222343-357.

Pitman, K.M., C.D. Tweedle, and M.Y. Cohen (1972) Branching of central neurons: intracellular cobalt injection for light and electron microscopy. Science 176:412.

Ritzmann, R.E.. and A.J. Pollack (1981) Motor responses to paired stimulation of @ant interneurons in the cockroach Perqdaneta americana. I. The dorsal interneurons. J . Comp. Physiol. IAI 1435-70 .

Ritzmann, R.E., A.J. Pollack, and M.L. Tobias 11982) Flight activity mediated by intracellular stimulation of dorsal giant interneurons of the cockroach Perqhneta arnericana. J. Comp. Physiol. \A] f47:313-322.

Homer, H., and V. Marquart (1984) Morphology and physiology of auditory interneurons in the metathoracic ganglion of the locust. J. Comp. Physiol. IAI 155249-262.

Thompson, K.J. 11986a) Oviposition digging in the grasshopper. I . Func- tional anatomy and the motor programme. J. Exp. Biol. 122387-411.

Thompson, K.J. ( 1986b3 Oviposition digging in the grasshopper. 11. Descend- ing neural control. J. Exp. Biol. 122:413-425.

Watson, A.H.D., and M. Burrows (1985) The distribution of synapses on the two fields of neurites of spiking local interneurones in the locust. J. Comp. Neurol. 240219-232.

Watson, A.H.D., and H.J. Pfluger 11987) The distribution of GABA-like immunoreactivity in relation to ganglion structure in the abdominal nerve cords of the locust (Schistocerca gregariai. Cell Tissue Res. 249:391-402.

Westin, J., J.J. Langberg, and J.M. Camhi (1977) Responses of giant interneurons of the cockroach Periplaneta americana to wind puffs of different directions and velocities. J. Comp. Physiol. IAl 121:307-324.

morphology and physiology of abdominal projection interneurones in the locust with mechanosensory...

Documents