Emergence of displacement activities in the male rat following thwarting of sexual behavior.

The present study revealed the emergence of displacement drinking and hindlimb scratching in noncopulating castrated male rats and in rats with medial preoptic (mPOA) lesions in tests with sexually attractive stimulus females. By contrast, sexually quiescent rats in the postejaculatory refractory period showed no evidence of displacement activity, and anestrous female rats displayed only moderate increments in drinking and scratching, compared with copulating estrous females. In both castrated and mPOA-lesion males, the amount of displacement activity was inversely related to strength of masculine sexual behavior, and in the former, displacement behavior was entirely suppressed by the subcutaneous implantation of a testosterone-filled Silastic capsule. When no stimulus female was present, no difference in drinking and scratching by control, castrated, and mPOA-lesion individuals could be discerned. Sexually inactive females elicited less displacement activity in castrated rats than did females in estrus. On the other hand, unreceptive stimulus females frequently elicited displacement behaviors in normal sexually active males. The results are discussed in relation to current concepts of the psychological organization of masculine sexual behavior, and it is suggested that the emergence of displacement behavior in castrated and mPOA-lesion males, and in normal males paired with anestrous females, may be due to the thwarting of sexual motivation.