Intraneuronal convergence of tactile and hormonal stimuli associated with female reproduction in rats.

Stimulation of the vagina and cervix, by mating or manual probing, elicits many behavioral and endocrine changes associated with female reproduction in rats. We and others have identified neurons in the medial preoptic area, medial division of the bed nucleus of the stria terminalis, posterodorsal portion of the medial amygdala, ventromedial hypothalamus, dorsomedial hypothalamus and midbrain central gray that increase Fos expression in response to vaginal-cervical stimulation (VCS). In the present study, we used a double-label immunofluorescent technique to determine if any of these VCS-responsive neurons also contained estrogen receptor-immunoreactivity. We found that over 80% of the VCS-induced Fos-IR neurons in the medial division of the bed nucleus of the stria terminalis also contained estrogen receptor-immunoreactivity. Furthermore, high percentages of VCS-responsive neurons in the medial preoptic area, posterodorsal medial amygdala, ventromedial hypothalamus and midbrain central gray contained estrogen receptor-immunoreactivity as well. These results suggest that sensory and hormonal information associated with female reproduction converge on specific populations of neurons and may be integrated at the molecular level within these neurons.