Synthesis of Neurosteroids and its Sexual Dimorphism in the Brain of Tilapia Oreochromis Mossambicus

Neurosteroids play a vital role in governing the physiology of reproduction next to neuropeptides and neurotransmitters. Gonadal development influences the steroid synthesis in Central Nervous System (CNS) and also the CNS regulates the gonadal steroid production. It is well known that the receptors of estrogen modulate the production of GnRH, and serotonin, dopamine and GABAergic neurons modulate the steroidogenic enzyme. However, the influence of neurosteroids, Estrogen (E2) and Testosterone (T), and its presence and synthetic pathway variations are not studied in detail in Tilapia. Hence, the present study of identifying various steroids present in the total and regions of Tilapia brain resulted in the quantitative difference in E2, T, 11-Ketotestosterone (11-KT), Androstenedione (A), DHEA, and 21-Hydroxyprogesterone (21-P). The reproductively active fishes of female brain shows the high quantity of testosterone when compare with the male brain. It has been derived that the Cyp19 and Cyp17 gene expressions are higher than the Cyp21 by which the pathway of progesteronal derivatives are not documented. The steroidal production in the incubated regions of Tilapia brain highlights the augmented presence of 5á-or 3á-reductase evidence the elimination pathway. The quantitative expression of mRNA analysis of 3á-HSD, 3â-HSD, Cyp17, Cyp19 and Cyp21 substantiate the variation in sex and maturation of gonadal stages. Aromatase indicate the shift in the sex dependent pathway. The sulphated steroids of pregnenalone and DHEA indicate the presence of Hydroxysteroid Sulfotransferase (HST) for purging action. The study suggests that the sexual modulation can be done at CNS through manipulating the steroidal receptors more particularly at thalamus region of brain.