5 Beta-reductase activity in the brain and cloacal gland of male and female embryos in the Japanese quail (Coturnix coturnix japonica).

Testosterone metabolism was studied by an in-vitro technique in the brain and cloacal gland of young male and female quail at different ages ranging from 7 days of incubation to 2 days after hatching. Very active metabolism, leading almost exclusively to the production of 5 beta-reduced compounds, was observed. 5 beta-Reductase activity remained high throughout the incubation period in the hypothalamus, decreased around the time of hatching in the cerebellum and decreased progressively between days 7 and 15 of incubation in the cloacal gland. These changes could be involved in the control of sexual differentiation: the high 5 beta-reductase in the brain possibly protects males from being behaviourally demasculinized by their endogenous testosterone while the decreasing 5 beta-reductase in the cloacal gland would progressively permit the masculinization of that structure.