INVOLVEMENT OF THE 5-HT2 RECEPTOR IN THE 5-HT RECEPTOR-MEDIATED STIMULATION OF PROLACTIN-RELEASE

The present study examined the involvement of 5-HT1C and 5-HT2 recepto rs in the regulation of prolactin release in the rat. Both the mixed 5 -HT2/5-HT1C receptor agonist, 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopr opane (DOI), and the preferential 5-HT1C agonist, 2-chloro-6-(1-pipera zinyl)pyrazine monohydrochloride (MK-212), elicited a significant incr ease in plasma prolactin concentration with DOI about 20 times more po tent than MK-212. Treatment with DOI, but not with MK-212, induced hea d twitching in the rat, and this behavior was inhibited by both the mi xed 5-HT2/5-HT1C receptor antagonist, ritanserin, and the selective 5- HT2 receptor antagonist, amperozide. DOI-induced prolactin release was also antagonized by ritanserin and amperozide, whereas only ritanseri n affected MK-212-induced prolactin release. Furthermore, amperozide d id not attenuate d-fenfluramine-elicited prolactin release, which is k nown to be antagonized by ritanserin. These data suggest that the phar macological stimulation of prolactin release by DOI is mediated via th e 5-HT2 receptor and that the 5-HT1C receptor may be of importance for the physiological regulation of prolactin release.