EFFECTS OF PACED MATING ON C-FOS GENE-EXPRESSION IN THE FEMALE RAT-BRAIN

When estrous female rats central or pace (P) their sexual contacts wit h males, several neuroendocrine and behavioral responses to mating occ ur that are not observed or are greatly attenuated after nonpaced mati ng. The present study examined whether the distribution and amount of FOS immunoreactivity (FOS-IR) induced in brain by mating would be alte red in females receiving paced rather than nonpaced mating stimulation . in the first experiment, females received 5 or 15 intromissions duri ng paced mating tests (5P and 15P), 5 or 15 intromissions during nonpa ced mating tests (5NP and 15NP), 15 mounts-without-intromission (MO) o r remained in their homecages (HC), Selective increases 1 h after pace d mating stimulation were observed in the posterodorsal medial amygdal a (MePD), where significantly more FOS-IR cells were present in the 5P and 15P groups than in the respective NP groups. The 5P, 5NP and 15NP had significantly more FOS-IR than the HC, MO, and 5NP groups, and th e 5P group had levels of FOS-IR which were equivalent to that seen in the 15NP group. In the posteromedial portion of the bed nucleus of the stria terminalis (BNSTpm) and the ventrolateral portion of the ventro medial nucleus of the hypothalamus (VMHvl), paced mating induced signi ficantly greater numbers of FOS-IR cells than did either MO or HG trea tments; increases induced by nonpaced mating were not statistically gr eater than HG controls. No differences between groups were seen in the medial preoptic area (mPOA). In the second experiment, experimentally lengthening the interintromission interval (III) as well as increasin g the intromission duration to mimic the characteristics of paced mati ng, resulted in significant increases in FOS-IR in the MePD but not in the other three brain regions. These results demonstrate that paced m ating is more effective in inducing c-fos expression than nonpaced mat ing, and that the MePD is particularly sensitive to differing characte ristics of the mating stimuli received.