septohippocampal projections
TRANSCRIPT
Septo-hippocampal projectionsMedial Septal complex (MS-DB) Three projection bundles, reciprocal
• Diagonal band of Broca – amygdaloid complex
• Induseum griseum – hippocampus, amygdala
• Fornix – subiculum, CA3
Induseum Griseum• Developmental remnant since the supra-diencephalic hippocampal
localization • Hippocampal projection to septum
MS-DB projection to hippocampus
• From ... MS-DB ipsilateral• Via -- Dorsal projection
pathway • Fibria hippocampi• Dorsal fornix • Supracallosal area
• To ... – SUB– CA3– DG
Neurotransmitters of MS-DB projections
• ………………………• GABA: Gabaergic long projection neurons (Leranth, 2007)
– Terminate with large clustered buttons on Parvalbumin positive cells (GABA interneurons) >> see theta-oscillation pacemaker cirquits
– Densely spiny cells at CA1-3 oriens and CA3 radiata– Sparsely spiny cells in DG – Dense innervation of supragranular zone in DG, Stratum oriens in CA3– Light innervation of hilus, stratum radiata CA3
Hippocampo-septal projections• CA3 to Lateral Septum
– Partly GABAergic – Bilateral
• Subiculum To Medial Septum– Glutamatergic – GABAergic– Ipsilateral
Both pathways preferentially terminate on GABAergic interneurons of septal nuclei
• Long-range projecting GABAergic neurons
…………………………...• Sparsely spiny / smooth
somata• Densely spiny / spiny
somata• Intermediate forms in
hilus
Classification of GABAergic long projection
hippocampo-septal neurons Class I II IIISomatostatin - - +Calbindin - + +mGluR1a + - -M2R + + -Dendritic projection
trilaminar Lamina resticted Lamina resticted
Somata location L-M Oriens OriensSpiking with theta
Out of phase In phase, regular, in trains
In phase, irregular, single spike
Spiking with ripples
Out In ?
Long Range GABA projections
• Hippocamposeptal long-range GABAergic projections
• Highly myelinized, more than Glutamatergic
• Conductance of IPSPs precede EPSPs ????