"There is evidence that D-Aspartate (D-Asp) modulates sex. hormone levels in frog testis by regulating the activity of P450. aromatase (P450 aro), the key enzyme which converts Testosterone (T) in. 17ß-Estradiol (E2). Here we report, for the first time, that there is a. direct correlation among brain levels of D-Asp, P450 aro, E2 and. Estradiol Receptor (ERα) in the male frogs during the reproductive as. well as the post-reproductive phases of the breeding cycle, with highest. levels being observed in the post-reproductive period. D-Asp i.p.. administration to frogs ready for reproduction, induced an increase of. brain P450 aro protein expression with concomitant enhancement of both E2. levels and ERα expression; at the same time, brain T levels and Androgen. receptor expression decreased. In contrast, in the post-reproductive. frogs, D-Asp treatment did not modify any of these parameters. Taken. together, these results imply that the regulation of P450 aro expression. by D-Asp could be an important step in the control of E2 levels in the. frog brain."