PARAVENTRICULAR NUCLEUS CONTROLS 5-HT2C RECEPTOR-MEDIATED CORTICOSTERONE AND PROLACTIN BUT NOT OXYTOCIN AND PENILE ERECTION RESPONSES

There is evidence that administration of the 5-HT2C receptor agonist, m-chlorophenylpiperazine (m-CPP), increases plasma concentrations of o xytocin, prolactin, corticosterone, induces penile erections and exces sive grooming in male rats. To test the hypothesis that the hypothalam ic paraventricular nucleus mediates these neuroendocrine and behaviour al responses, we measured the effects of m-CPP (0.6 mg/kg i.v.) an the se parameters in chronically cannulated, freely moving male rats after surgical lesion of the paraventricular nucleus or sham operation. Par aventricular nucleus lesion markedly attenuated prolactin, corticoster one and excessive grooming, but not oxytocin and penile erection respo nses to m-CPP. In contrast, both oxytocin and corticosterone responses to the dopamine receptor agonist, apomorphine (0.05 mg/kg i.v.), were attenuated in lesioned rats. The present studies suggest that the par aventricular nucleus mediates m-CPP-induced prolactin, corticosterone and probably also excessive grooming responses, and the mechanisms of apomorphine and m-CPP action on oxytocin secretion and penile erection responses differ.