FOS-IMMUNOREACTIVITY WITHIN THE EXTENDED AMYGDALA IS CORRELATED WITH THE ONSET OF SEXUAL SATIETY

We hypothesized that c-fos expression in the medial amygdala (Me), the bed nucleus of the stria terminalis (BNST), and the medial preoptic a rea (MPOA) of the male Syrian hamster brain correlated with sexual sat iety. To address this hypothesis, males were mated for 4 consecutive d ays. Experiment 1 determined whether the number of Fos-immunoreactive (Fos-ir) nuclei was equivalent in two groups of males mated to sexual satiety, one group of rested males (9.67 +/- 0.80 ejaculations) and a second group mated for 4 consecutive days (3.50 +/- 0.56 ejaculations) . Fos-ir was increased within the caudal posterodorsal Me (cMePD), the anterodorsal and posteroventral subdivisions of the posteromedial BNS T [BNSTpm(ad) and BNSTpm(pv)], the dorsolateral MPOA, and the medial p reoptic nucleus of all males mated to sexual satiety compared to nonma ted controls. In addition, Fos-ir ''clusters'' within the cMePD and BN STpm(ad) were present in males mated to satiety regardless of the numb er of ejaculations. However, all males achieved multiple ejaculations. Therefore, Experiment 2 examined whether two groups of males stopped at one ejaculation exhibit different patterns of Fos-ir depending on p roximity to sexual satiety. Brains of consecutively mated males, close r to satiety than rested males, showed greater BNSTpm(pv) Fos-ir and 5 /6 mates, but no rested male, exhibited cMePD Fos-ir clusters. These r esults support the hypothesis that cMePD and BNSTpm(pv) neuronal activ ation is associated with satiety and may constitute a discrete circuit to terminate mating. (C) 1998 Academic Press.