1. SEXUAL DIMORPHISMS IN NERVE TISSUE and EXPERIMENTAL MODELS

2. During , in a socially sensitive environment, some investigations identified neuroendocrine areas controlling sexual behavior.
These regions are sexually dimorphic.
Initially, the neuroendocrine basis of the sexual behavior were studied analysing the final aspect of the behavior, the copulation in males and the receptivity, lordosis, in females.
Now we know that specific cerebral regions and neurochemical systems are implicated in the control of the male and female sexual behavior.

4. EXAMPLE: MALE SEXUAL BEHAVIOR
It is subdivisibile in two components:
appetitive component (courtship and mount attempts)
consummatory component (mount, intromission and eiaculation).
Intromission and eiaculation activate a lower number of neural circuits than the appetitive phase when the male should control the strategies for the courtship.
There are obvious dimorphisms, analyzed from specific experimental models, and other dimorphisms less obvious in which the integration of olfactory, visual, tactil, and hormonal may induce complex motor behaviors.
It is important to study different experimental models.
Each model clarify a specific situation, a single behavior

5. When can we use the terminology of dimorphism? …………….
Sex differences are not only morphological but also physiological.
These differences are organizational (they appear during the development and are irreversible) and are determined during a limited period of the perinatal life (critical period).
Dimorphic nervous areas may control dimorphic behaviors.
These areas can be influenced by neonatal hormonal manipulation.

6. THE SPINAL CORD

7. Male rat

8. Lombar level

9. RAT
Spinal cord
L5,L6
Nuclei controlling the penis erection are dimorphic:
- Dorsolateral nucleus (DLN) innervates ischiocavernosus muscle
- Spinal nucleus of bulbocavernosus (SNB)
innervates bulbocavernosus and levator ani muscles
These neurons concentrate T and DHT, not E2
Retrodorsolateral nucleus (RDLN) that contributes to constitute the sciatic nerve is not dimorphic

10. Is the dimorphism linked to hormonal environment? ……..
SNB MODEL IN RAT
EXPERIMENTAL DESIGN
Adult gonadectomized male and female rats subcutaneously injected with testosterone propionate (TP) for 28 days
Tfm rats
- Anesthesia, perfusion with fixative, dissection, sectioning with cryostat, thionin staining, counting of the cell number and soma area

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