title: Role of the dopaminergic, serotonergic and cholinergic link in the expression of penile erection in rats.
abstract: The neural mechanisms underlying the penile erection induced by serotonergic, cholinergic and dopaminergic stimulants were comparatively investigated. Fenfluramine (0.1-10 mg/kg, i.p.), pilocarpine (0.032-3.2 mg/kg) and apomorphine (0.01-1 mg/kg) induced penile erection in rats with bell-shaped dose-response curves. The penile erection induced by fenfluramine (1 mg/kg) was dose-dependently antagonized by pindolol (0.1-3.2 mg/kg), a 5-HT1 antagonist, or scopolamine (0.032-1 mg/kg), a muscarinic antagonist, but not by sulpiride (1-32 mg/kg), a dopaminergic antagonist. The penile erection induced by pilocarpine (0.32 mg/kg) was countered by pindolol or scopolamine but not by sulpiride, while that induced by apomorphine (0.032 mg/kg) was countered by all three antagonists. Septo-hippocampal cholinergic deafferentations by medial septum lesioning or fimbria-fornix transection also significantly attenuated the penile erection induced by fenfluramine or apomorphine, but scarcely affected that induced by pilocarpine. Raphe lesion by injections of 5,7-dihydroxytryptamine, a serotonergic neurotoxin, into the median- and dorsal-raphe nuclei significantly attenuated the penile erections induced by fenfluramine and apomorphine but not that by pilocarpine. These results suggest that a neuronal link between the dopaminergic, serotonergic and cholinergic systems plays a crucial role in the expression of penile erection; dopaminergic stimulation causes an activation of the raphe serotonergic neurons which in turn enhances the septo-hippocampal cholinergic pathway and results in expression of penile erection.
authors.affiliation: Tsukuba Research Laboratories, Fujisawa Pharmaceutical Co., Ltd., Ibaraki, Japan.
authors.forename: N
authors.initials: N
authors.lastname: Maeda
authors.forename: N
authors.initials: N
authors.lastname: Matsuoka
authors.forename: I
authors.initials: I
authors.lastname: Yamaguchi
mesh_terms: D000818:Animals; D003714:Denervation; D004298:Dopamine / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D006624:Hippocampus / Q000502:physiology; D008297:Male; D009475:Neurons, Afferent / Q000187:drug effects; D010275:Parasympathetic Nervous System / Q000187:drug effects / Q000502:physiology*; D010410:Penile Erection / Q000187:drug effects / Q000502:physiology*; D010869:Pindolol / Q000494:pharmacology; D011903:Raphe Nuclei / Q000502:physiology; D051381:Rats; D011916:Rats, Inbred F344; D012601:Scopolamine / Q000494:pharmacology; D012701:Serotonin / Q000502:physiology*; D013469:Sulpiride / Q000494:pharmacology
chemical_list: D012701:Serotonin; D013469:Sulpiride; D010869:Pindolol; D012601:Scopolamine; D004298:Dopamine