title: Effects of GABA-ergic drugs on penile erection induced by apomorphine in rats.
abstract: The effects of GABA agonists and antagonists on penile erection (PE) induced by apomorphine were investigated in rats. Subcutaneous (SC) administration of apomorphine (0.01-0.1 mg/kg) induces a dose-dependent PE in rats. The maximum effect was obtained with 0.1 mg/kg of the drug. The response was decreased with increasing doses of apomorphine from 0.1 to 0.5 mg/kg. The response induced by apomorphine (0.1-0.5 mg/kg) was decreased in animals pretreated with either the GABA-A agonist muscimol or the GABA-B agonist baclofen. Combination of muscimol with baclofen caused a stronger inhibitory effect on apomorphine-induced PE. Bicuculline or picrotoxin but not phaclofen reduced the inhibitory effect of muscimol on PE induced by apomorphine, whereas phaclofen but not GABA-A antagonists decreased the inhibitory action of baclofen on apomorphine-induced PE. Pretreatment of animals with higher doses of the GABA-A antagonists bicuculline and picrotoxin or the GABA-B antagonist phaclofen elicited inhibition of apomorphine-induced PE. However, the inhibitory effects of GABA-A and GABA-B antagonists are lost on combination. Administration of GABA-A and GABA-B receptor stimulation inhibit PE induced by dopaminergic mechanism(s).
authors.affiliation: Department of Pharmacology, School of Medicine, University of Tehran, Iran.
authors.forename: M R
authors.initials: MR
authors.lastname: Zarrindast
authors.forename: H
authors.initials: H
authors.lastname: Farahvash
mesh_terms: D000818:Animals; D001058:Apomorphine / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D001418:Baclofen / Q000494:pharmacology; D004298:Dopamine / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D018755:GABA Agonists / Q000494:pharmacology*; D018756:GABA Antagonists / Q000494:pharmacology*; D058785:GABA-A Receptor Agonists; D058787:GABA-A Receptor Antagonists; D058786:GABA-B Receptor Agonists; D058788:GABA-B Receptor Antagonists; D008297:Male; D009118:Muscimol / Q000494:pharmacology; D010410:Penile Erection / Q000187:drug effects*; D051381:Rats
chemical_list: D018755:GABA Agonists; D018756:GABA Antagonists; D058785:GABA-A Receptor Agonists; D058787:GABA-A Receptor Antagonists; D058786:GABA-B Receptor Agonists; D058788:GABA-B Receptor Antagonists; D009118:Muscimol; D001418:Baclofen; D001058:Apomorphine; D004298:Dopamine