CASTRATION DECREASES EXTRACELLULAR, BUT INCREASES INTRACELLULAR, DOPAMINE IN MEDIAL PREOPTIC AREA OF MALE RATS

Dopamine (DA) is released in the medial preoptic area (MPOA) of male r ats in the presence of a female, and it facilitates male sexual behavi or. Castration blocks the DA response to a female and the male's abili ty to copulate. The present experiments examined the effects of castra tion on (1) basal levels of extracellular DA in the MPOA, using the no net flux microdialysis technique, (2) the response of extracellular D A to amphetamine, and (3) tissue levels of DA. Castrated rats had lowe r basal levels of extracellular DA in the MPOA, compared with gonadall y intact rats; in vivo recovery, a measure of uptake, was not differen t. This suggests that castration decreases DA release in basal conditi ons, as well as in response to a female. However, systemic amphetamine injections, which induce DA release, resulted in greater DA release i n castrates. Finally, tissue levels of DA were higher in the MPOA, the caudate-putamen and the bed nucleus of stria terminalis of castrates. These data suggest that DA synthesis and storage in the MPOA are norm al, or even enhanced, in castrates, and uptake is not altered. The def icit in extracellular levels appears to be related to release, perhaps due to decreased nitric oxide. (C) 1998 Elsevier Science B.V.