DIFFERENTIAL INDUCTION OF FOS IN THE FEMALE RAT-BRAIN FOLLOWING DIFFERENT AMOUNTS OF VAGINOCERVICAL STIMULATION - MODULATION BY STEROID-HORMONES

Vaginocervical stimulation (VCS), produced either by copulation with i ntromission or by manual stimulation of vagina and cervix with a glass rod, induces neuroendocrine and behavioral responses that are critica l for female reproduction in many species. We and others have shown th at Fos mRNA and protein are induced within different estrogen-concentr ating and -non-concentrating regions of the female rat brain following copulation with intromission and manual VCS. Zn the present study, we investigated the amount of distributed VCS required to induce Fos imm unoreactivity within estrogen-concentrating regions of the medial preo ptic area, lateral septum, bed nucleus of the stria terminalis, ventro medial hypothalamus, medial amygdala, and mesencephalic central gray, and whether estrogen and progesterone could alter the threshold or pat tern of induction. Ovariectomized rats were administered estradiol ben zoate (10 mu g) 48 h and progesterone (500 mu g) 4 h before receiving either 0, 1, 5, 10, 20, 30, 40, or 50 manual VCSs with a lubricated gl ass rod. Ovariectomized hormone control rats received injections of th e sesame oil vehicle 48 and 4 h before VCS. All rats were sacrificed 7 5 min after the first VCS. Fos immunoreactivity was induced differenti ally by VCS within the different regions, and the hormones either augm ented, inhibited, or had no effect on the induction. These data demons trate that cells within different estrogen-concentrating regions of th e female rat brain are differentially sensitive to VCS, and that stero id hormones can either increase or decrease the amount of Fos induced by different amounts of VCS. Different brain regions may participate i n gating the sensory information of VCS into different behavioral and neuroendocrine events.