5-HT2A/2C Receptors and lordosis behavior in the female rat

Abstract

The effects of hypothalamic infusion of serotonin (5-HT)2A/2C receptor compounds on lordosis behavior were examined in ovariectomized, hormone-primed (0.5 $\mu$g estradiol benzoate, subcutaneuosly (s.c.), followed 48 hr later with 500 $\mu$g progesterone, s.c.) rats. This hormone-priming condition resulted in some rats that were sexually receptive and some that showed low or no sexual behavior. Sexually receptive rats were inhibited when the 5-HT$\rm\sb{2A/2C}$ receptor antagonist, 3-(2-) 4-(4-fluorobenzoyl)-1-piperdinlyl(ethyl) -2,4(1H,3H)-quinazo-linedione tartrate, ketanserin, was infused into the ventromedial nucleus of the hypothalamus (VMN). Hormone-primed ovariectomized rats were more affected by the drug than were proestrous rats. The reason for this apparent difference in sensitivity to the drug is unknown. When ovariectomized, hormone-primed rats with low sexual receptivity received VMN infusion with the 5-HT$\rm\sb{2A/2C}$ receptor agonist, ($\pm$)-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane HCl, DOI, sexual behavior increased. Similar increases in lordosis behavior were observed following infusion with the mixed 5-HT receptor compounds, 2-(1-piperazinyl) quinoline dimaleate, quipazine, and N-(3-trifluoromethyl-phenyl) piperazine hydrochloride, TFMPP. Facilitation of the behavior occurred within 15-20 min of agonist infusion, while inhibition following antagonist infusion occurred more rapidly. These findings are consistent with the hypothesis that 5-HT$\rm\sb{2A/2C}$ receptors in the VMN contribute to the facilitation of female rat sexual behavior.