| The results of the present experiments showed the inhibitory effects of serotonin (5-HT) receptor stimulation, in the anterior lateral hypothalamus (LHAA), on sexual behavior in the male rat. Stimulation and blockade of the 5-HT1A, 5-HT1B and 5-HT2A receptors were evaluated.; Microinfusion of the 5-HT1A agonist, (+/-)-2-dipropylamino-8-hydroxy-1,2,3,4-tetrahydronaphthalene hydrobromide (8-OH-DPAT), facilitated male copulatory behavior. The facilitation produced by 8OH-DPAT could not be blocked by the 5-HT1A antagonist, 4-iodo-N-[2-[4-(methoxyphenyl)-1-piperazinyl]-N-2-pyridinyl-benzamide hydrochloride (MMPI). There was no dose of the 5-HT1B agonist, 7-Trifluoromethyl-4(4-methyl-1-piperazinyl)-pyrrolo[1,2-a]quinoxaline maleate (CGS 12066), that inhibited copulation without accompanying motor deficits. Microinfusion of an effective dose of the 5-HT2A/2C agonist R(+)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane hydrochloride (DOI), inhibited male rat copulatory behavior and the inhibition was blocked with the 5-HT2A antagonist, 6-methyl-1-(1-methylethyl)-ergoline-8-carboxylic acid(8beta)-2-hydroxy-1-methylpropyl ester (Z)-2-butenedioate (LY-53,857). Systemic administration of LY-53857, either preceding or following microinfusion of DOI, was unable to block the inhibitory effects produced by DOI. These data suggest that 5-HT2A receptors in the LHAA contribute to inhibition of male rat copulatory behavior. |
