FOS EXPRESSION IN THE RAT-BRAIN FOLLOWING VAGINAL-CERVICAL STIMULATION BY MATING AND MANUAL PROBING

Vaginal-cervical stimulation (VCS), provided by mating or manual probi ng, induces many reproductive behavioral and endocrine changes in fema le rats. These changes include an increase in lordosis duration, heat termination and pseudopregnancy. Electrophysiological and [C-14]2-deox y-D-glucose studies collectively show that neurons in the medial preop tic area, ventromedial hypothalamus and midbrain central gray respond to manual VCS. In the present study we immunocytochemically labeled br ain sections for Fos, the protein product of the immediate early gene c-fos, to detect VCS-responsive neurons in hormone-primed animals rece iving VCS by mating or manual probing. In Experiment 1, females receiv ing mounts and intromissions were compared to: 1) vaginally-masked fem ales receiving mounts but no VCS, 2) females exposed to an intact anes thetized male or 3) females not exposed to males or the testing arena. Those animals receiving VCS showed a dramatic increase in the number of Fos-immunoreactive cells in the medial preoptic area, posterodorsal portion of the medial amygdala and bed nucleus of the stria terminali s, as well as the dorsomedial hypothalamus, ventromedial hypothalamus and midbrain central gray. These effects of VCS were confirmed in Expe riment 2 in animals receiving manual vaginal-cervical probing. These f indings extend previous electrophysiological and [C-14]2-deoxy-D-gluco se studies by providing evidence that additional brain areas respond t o VCS by mating, as well as manual probing.