DEMONSTRATION OF EJACULATION-INDUCED NEURAL ACTIVITY IN THE MALE-RAT BRAIN USING 5-HT1A AGONIST 8-OH-DPAT

Previous studies from our laboratory indicated the existence of ejacul ation-related neural activation within the circuitry underlying matin, o behavior in the male rat. Clusters of Fos-immunoreactive neurons wer e present only following ejaculations and not after intromissions. How ever, it was not clear if this pattern of neural activation was specif ic to ejaculation or a result of summation of sexual activity precedin g ejaculation. In the present study, the facilitative effect of the 5- HT1A receptor agonist 8-OH-DPAT on ejaculatory behavior was used to an alyze the pattern of Fos immunoreactivity following ejaculation preced ed by minimal sexual activity. Male rats treated with 8-OH-DPAT (0.4 m g/kg) achieved ejaculation after a shortened latency and low numbers o f mounts and intromissions. Ejaculation-induced Fos immunoreactivity w as present in clusters of neurons in the lateral part of the posterodo rsal medial amygdala, in two subregions of the posteromedial bed nucle us of the stria terminalis, in the posterodorsal preoptic nucleus, and in the parvicellular part of the subparafascicular thalamic nucleus. Males that ejaculated with the first intromission and were treated wit h a higher dose of 8-OH-DPAT (0.8 mg/kg) exhibited similar clusters of Fos-positive neurons in all areas except the posterodorsal preoptic n ucleus. The results demonstrate the existence of a specific ejaculatio n-related subcircuit within a larger neural circuitry involved in male sexual behavior. (C) 1997 Elsevier Science Inc.