The influence of steroid hormones on competing sexual and ingestive behavior in the male rat.

Water replete rats allowed restricted access to a sweet nonnutritive solution (0.2% Acesulfame-K) spend about one third of their time drinking it. This ingestive response is markedly inhibited if the male rat is simultaneously presented with an estrous female, but not an anestrous female or another male, despite the fact that there is sufficient time for both sexual and ingestive behaviors to occur. Castration and the subsequent decline in sexual behavior is accompanied by an increase in Acesulfame ingestion in the presence of a receptive female. Treatment with testosterone reverses both these effects. Similarly treatment of castrate males with DHT and estradiol (the active metabolites of testosterone) maintains both full sexual behavior and suppression of the ingestive response. However, the steroid requirements for sexual activity do not correspond completely with those for the sexually-induced suppression of ingestive behavior. Treatment of castrate males with estradiol alone maintains mounting behavior (but no intromissions or ejaculations) but does not suppress ingestive behavior in the presence of a receptive female--indeed under these suboptimal hormone conditions sexual behavior appears to be reduced in the presence of Acesulfame. Steroid hormones, therefore, have at least two effects upon sexual behavior. They enable certain aspects of sexual behavior such as intromissions and ejaculations, and also alter the animal's priority of response to two competing (ingestive and sexual) stimuli.