Please be advised that this information was generated on 2018-05-12 and may be subject to change. BRAIN RESEARCH

Abstract-In the present study a detailed quantitative analysis was made using Fos as a marker for neural activation to define which subregions in the neural circuitry underlying male sexual behavior are involved in display of anogenital investigation versus copulation. Neural activity was differentially distributed following anogenital investigation versus mating and was restricted to specific subdivisions that form a heavily interconnected network. Cliemosensory investigation increased neural activity in the postero medial subdivision of the bed nucleus of the stria terminalis and the posterodorsal subdivision of the medial amygdala, bruin regions that receive chcmosensory signals processed through the olfactory bulbs, presumably reflecting the acquisition of cliemosensory signals or the display of anogenital investigation. However, other sensory signals or sexual experience may also have contributed to the induction of neural activation in these brain areas. Moreover, consummatory behavior increased neural activity in the subparafaseicular nucleus, a brain region that receives genital sensory inputs. In turn, this brain region projects to the medial preoptic nuclcus and posterior nucleus of the amygdala, where neural activity was also abundant only following copulation, In addition, clusters of neurons were activated in the posteromedial subdivision of the bed nucleus of the stria terminalis and posterodorsal subdivision of the medial amygdala following consummatory behavior.The present study provides an anatomically detailed picture about the distribution of neural activation following sexual behavior in the rat, specifically in relation to differences following anogenital investi gation versus mating. «";) 1997 IBRO. Published by Elsevier Science Ltd.

The medial preoptic nucleus (MPN) is an essential site for the regulation of male sexual behavior. Previous studies using c-fos as a marker for neural activation have shown that copulation increased c-fos expression in the MPN. Neural activation was also present in brain regions that are connected with the MPN and are involved in male sexual behavior, including the posteromedial bed nucleus of the stria terminalis (BNSTpm), posterodorsal preoptic nucleus (PD), posterodorsal medial amygdala (MEApd), and parvocellular subparafascicular thalamic nucleus (SPFp). The present study investigated whether the copulation-induced, activated neurons in these brain regions are involved in the bidirectional connections with the MPN. Therefore, mating-induced Fos expression was combined with application of anterograde (biotinylated dextran amine) or retrograde (cholera toxin B subunit) tracers in the MPN. The results demonstrated that neurons in the BNSTpm, PD, MEApd, and SPFp that project to the MPN were activated following copulation. However, in males that displayed sexual behavior but did not achieve ejaculation, few double-labeled neurons were evident, although both retrogradely labeled neurons and Fos-immunoreactive cells were present. In addition, retrograde neurons that expressed Fos were located in discrete subdivisions within the brain regions studied, where Fos is induced after ejaculation. Likewise, anterogradely labeled fibers originating from the MPN were not distributed homogeneously but were particularly dense in these discrete subdivisions. These results demonstrate that copulation-induced Fos-positive neurons in specific subdivisions of the BNSTpm, PD, MEApd, and SPFp have bidirectional connections with the MPN. Taken together with previous findings, this supports the existence of a discrete subcircuit within a larger neural network underlying male sexual behavior.

No abstract

No abstract