SEXUAL DIMORPHISMS IN SEXUAL DIMORPHISMS IN NERVE TISSUENERVE TISSUE

andandEXPERIMENTAL MODELSEXPERIMENTAL MODELS

• During 1970-1990, in a socially sensitive During 1970-1990, in a socially sensitive environment, some investigations identified environment, some investigations identified neuroendocrine areas controlling sexual behavior.neuroendocrine areas controlling sexual behavior.

• These regions are sexually dimorphic.These regions are sexually dimorphic.

• Initially, the neuroendocrine basis of the sexual Initially, the neuroendocrine basis of the sexual behavior were studied analysing the final aspect of behavior were studied analysing the final aspect of the behavior, the copulation in males and the the behavior, the copulation in males and the receptivity, lordosis, in females.receptivity, lordosis, in females.

• Now we know that specific cerebral regions and Now we know that specific cerebral regions and neurochemical systems are implicated in the control of neurochemical systems are implicated in the control of the male and female sexual behavior.the male and female sexual behavior.

EXAMPLE: MALE SEXUAL BEHAVIOREXAMPLE: MALE SEXUAL BEHAVIOR

It is subdivisibile in two components:It is subdivisibile in two components:- appetitive component (courtship and mount attempts)appetitive component (courtship and mount attempts)- consummatory component (mount, intromission and consummatory component (mount, intromission and eiaculation).eiaculation).

Intromission and eiaculation activate a lower number Intromission and eiaculation activate a lower number of neural circuits than the appetitive phase when the of neural circuits than the appetitive phase when the male should control the strategies for the courtship.male should control the strategies for the courtship.

• There are obvious dimorphisms, analyzed from There are obvious dimorphisms, analyzed from specific experimental models, and other dimorphisms specific experimental models, and other dimorphisms less obvious in which the integration of olfactory, less obvious in which the integration of olfactory, visual, tactil, and hormonal may induce complex motor visual, tactil, and hormonal may induce complex motor behaviors.behaviors.

• It is important to study different experimental It is important to study different experimental models.models.

• Each model clarify a specific situation, a single Each model clarify a specific situation, a single behaviorbehavior

• When can we use the terminology of dimorphism? When can we use the terminology of dimorphism? …………….…………….

• Sex differences are not only morphological but Sex differences are not only morphological but also physiological.also physiological.

• These differences are organizational (they appear These differences are organizational (they appear during the development and are irreversible) and during the development and are irreversible) and are determined during a limited period of the are determined during a limited period of the perinatal life (critical period).perinatal life (critical period).• Dimorphic nervous areas may control dimorphic Dimorphic nervous areas may control dimorphic behaviors.behaviors.

• These areas can be influenced by neonatal These areas can be influenced by neonatal hormonal manipulation.hormonal manipulation.

THE SPINAL CORDTHE SPINAL CORD

Male ratMale rat

Lombar levelLombar level

•Nuclei controlling the Nuclei controlling the penis erection are penis erection are dimorphic:dimorphic:

- Dorsolateral nucleus - Dorsolateral nucleus (DLN) innervates (DLN) innervates ischiocavernosus muscleischiocavernosus muscle

- Spinal nucleus of - Spinal nucleus of bulbocavernosus (SNB)bulbocavernosus (SNB)innervates innervates bulbocavernosus and bulbocavernosus and levator ani muscleslevator ani muscles

These neurons These neurons concentrate T and DHT, concentrate T and DHT, not Enot E22

•Retrodorsolateral Retrodorsolateral nucleus (RDLN) that nucleus (RDLN) that contributes to contributes to constitute the sciatic constitute the sciatic nerve is not dimorphicnerve is not dimorphic

Spinal cordSpinal cordL5,L6

RAT

SNB MODEL IN RATSNB MODEL IN RAT

EXPERIMENTAL DESIGNEXPERIMENTAL DESIGN

- Adult gonadectomized male and female rats Adult gonadectomized male and female rats subcutaneously injected with testosterone propionate subcutaneously injected with testosterone propionate (TP) for 28 days(TP) for 28 days

-Tfm ratsTfm rats

- Anesthesia, perfusion with fixative, dissection, - Anesthesia, perfusion with fixative, dissection, sectioning with cryostat, thionin staining, counting sectioning with cryostat, thionin staining, counting of the cell number and soma areaof the cell number and soma area

Is the dimorphism linked to hormonal environment? ……..

SNB

Gonadectomy and treatment with Testosterone (T) of Gonadectomy and treatment with Testosterone (T) of adults do not alter the dimorphism in male and femaleadults do not alter the dimorphism in male and female