Sexual changes in the neurosteroids of Indian major carp, Labeo rohita (Ham.)

The synthesis of steroids in different regions of the fish brain needs to be studied in order to understand the control mechanism of neurosteroids on reproduction in both males and females. In the present study, the synthesis of sex steroids testosterone (T) and estradiol-17b (E2) was studied in different regions of the brain in the carp L. rohita, by using 17a-OHprogesterone (17a-OHP) as a precursor in in vitro incubations. A sex dependent difference was observed at the conversion level of T and E2. Further study, conducted using brain incubations with labelled androstenedione, revealed that aromatization is higher in the female brain as compared to the male brain. Also, the result suggests that the aromatase enzymes are region specific. These results lead to an improved understanding of the neurosteroidal control of sexual dimorphism in fishes.