REPRODUCTIVELY-RELEVANT STIMULI INDUCE FOS-IMMUNOREACTIVITY WITHIN PROGESTIN RECEPTOR-CONTAINING NEURONS IN LOCALIZED REGIONS OF FEMALE RATFOREBRAIN

An experiment was conducted to determine if neurons that respond to st imuli associated with mating in female brain also contain progestin re ceptors. We found that a portion of the neurons that respond to stimul i associated with mating also contains progestin receptors. While the appropriate hormonal conditions are important for sexual receptivity, somatosensory information provided by the male also influences sexual behavior. One important stimulus provided by the male during copulatio n is vaginal-cervical stimulation (VCS). VCS has been shown to elicit many different behavioral and endocrine changes in female rats, such a s increases in lordosis, pseudopregnancy, and termination of sexual re ceptivity. VCS also increases the expression of the immediate early ge ne product, Fos, in areas associated with reproduction. A portion of t he neurons responding to VCS with increased Fos-immunoreactivity (Fos- IR) in female rat forebrain also contains estrogen receptors, illustra ting that hormonal and mating-stimuli converge in a population of cell s. As progesterone also plays an important role in female sex behavior , it is important to determine if some of the neurons also integrate i nformation concerning serum progesterone levels and social interaction s. Thus, we used a dual immunofluorescent technique to label both Fos- IR and progestin receptor-immunoreactivity (PR-IR) in the brains of es tradiol-primed, ovariectomized female rats following VCS manually appl ied by the experimenter. Many of the neurons that respond to VCS with increased Fos-IR within the medial preoptic area, the arcuate nucleus, and the progestin receptor-rich areas of the rostral and caudal ventr omedial nucleus of the hypothalamus also contain PR-IR.