AROMATASE-ACTIVITY IN THE PREOPTIC AREA DIFFERS BETWEEN AGGRESSIVE AND NONAGGRESSIVE MALE HOUSE MICE

Treatment with testosterone (T) or estradiol (E(2)) facilitates intras pecific aggressive behavior in adult rodents. Brain aromatization of T to E(2) appears to be involved in facilitation of fighting behavior. In the present study we measure the in vitro brain aromatase activity (AA) in the preoptic area (POA), amygdaloid nuclei (Am), ventromedial hypothalamus (VMH), and parietal cortex (CTX) from two strains of adul t male house mice, which were genetically selected for territorial agg ression, based upon their attack latencies (short attack latency: SAL; long attack latency: LAL). The results reveal a higher AA in the POA of nonaggressive LAL males, as compared to aggressive SAL animals. The POA AA is, thus, inversely correlated with aggressiveness. The AA lev els in both the VMH and Am do not differ significantly between strains . Furthermore, a differential brain area-specific AA distribution exis ts: POA > VMH AA in LAL, whereas POA < VMH in SAL. In both selection l ines, the Am exhibits the highest levels of AA, as compared to the oth er investigated areas. Kinetic studies revealed that the aromatase K-m is similar in both strains. The results indicate that the strain diff erence in AA is specific to the POA, but is not necessarily positively correlated with circulating plasma T levels. Other factors, in additi on to androgen, are probably involved in the regulation of POA aromata se. We suggest that a higher neural androgen receptor sensitivity exis ts in the POA of nonaggressive LAL males, resulting in higher adult PO A AA, despite lower concentrations of circulating T.