SEXUAL DIMORPHISMS IN NERVE TISSUE and EXPERIMENTAL MODELS

During 1970-1990, 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.

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

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.

THE SPINAL CORD

Male rat

Lombar level

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

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

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