Medial preoptic and anterior hypothalamic lesions: influences on aggressive behavior in female hamsters.

Bilateral radio-frequency lesions in the medial preoptic area (MPOA) were found to reduce aggressiveness and to increase the incidence of submissive responding in female hamsters that were paired against other females. The reduced aggressiveness of females with MPOA lesions appeared to be relatively independent of their hormonal state, since ovariectomy and subsequent replacement therapy with 200 μg a day of testosterone propionate (TP) had no influence on the low levels of aggression exhibited by these females. In contrast to females with lesions in the MPOA, females with lesions in anterior hypothalamus (AHA) exhibited increased aggressiveness in the postoperative tests preceding ovariectomy. Ovariectomy reduced the frequency with which AHA-lesioned females exhibited fights, attack-chase sequences, and low intensity aggressive acts, and TP injections failed to reinstate precastration levels of these behaviors.