STIMULATION OF 5-HT(1A) AND 5-HT(2)/5-HT(1C) RECEPTORS INDUCE OXYTOCIN RELEASE IN THE MALE-RAT

Plasma oxytocin responses to the 5-HT1A receptor agonists 8-hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT), buspirone and ipsapirone, and the 5-HT2/5-HT1C receptor agonist 1-(2,5-dimethoxy-4-iodophenyl)2-aminopropane (DOI) have been studied in conscious, freely moving male rats. All four compounds caused dose-related increases in plasma oxytocin concentrations after intravenous administration. Oxytocin responses to 8-OH-DPAT were significantly attenuated by pretreatment with the 5-HT1A receptor antagonist NAN-190 while responses to DOI were blocked by pretreatment with the 5-HT2/5-HT1C receptor antagonist ritanserin. Since vasopressin concentration did not change despite the marked elevation in plasma oxytocin, these results suggest that 5-HT1A and 5-HT2/5-HT1C receptors all stimulate oxytocin secretion, and this effect does not reflect a general neurohypophyseal hormone release.