title: Alpha 2-adrenoceptor antagonists and male sexual behavior: II. Erectile and ejaculatory reflexes.
abstract: Three alpha 2-adrenoceptor antagonists, yohimbine, idazoxan, and imiloxan, all shown to have stimulatory effects on sexual arousal/motivation, were studied to identify their possible effects on the other two major components of male copulatory behavior: erection and ejaculation. Genital reflex ex copula tests were used in order to assess these two responses without the confounding factors of mating behavior. Dose ranges were yohimbine: 0.25-4.0 mg/kg; idazoxan: 1.0-8.0 mg/kg; and imiloxan: 12.5-50.0 mg/kg. Lower doses of two of the drugs significantly enhanced the frequency of erections, while the third (yohimbine) showed a strong trend in that direction. At higher doses, all three alpha 2-antagonists produced significant reductions in the number of rats showing penile reflexes, including both erections and ejaculations. In those rats which did show penile reflexes, higher doses of yohimbine (4.0 mg/kg) inhibited the frequency of erections, while the higher dose of idazoxan showed a trend towards such inhibition. Thus, profound, largely inhibitory effects of these agents were demonstrated at dose ranges which have been shown to enhance sexual arousal. These data indicate that within the nervous system alpha 2-adrenoceptor antagonists can modulate erectile and ejaculatory mechanisms quite independently from effects on arousal/motivation.
mesh_terms: D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology*; D000818:Animals; D004146:Dioxanes / Q000494:pharmacology; D004542:Ejaculation / Q000187:drug effects; D019329:Idazoxan; D007093:Imidazoles / Q000494:pharmacology; D008297:Male; D010410:Penile Erection / Q000187:drug effects; D051381:Rats; D012018:Reflex / Q000187:drug effects; D012726:Sexual Behavior, Animal / Q000187:drug effects*; D015016:Yohimbine / Q000494:pharmacology
chemical_list: D000317:Adrenergic alpha-Antagonists; D004146:Dioxanes; D007093:Imidazoles; D015016:Yohimbine; D019329:Idazoxan; C044484:Imiloxan