Opposite influences of dopaminergic receptor subtypes on penile erection.
1. Mixed D-1/D-2 dopamine agonist apomorphine induced a penile erection (PE) in rats in a biphasic manner. 2. The response was decreased with increasing doses of the drug. 3. The maximum effect was obtained by 0.1 mg/kg of apomorphine. 4. In animals pretreated with D-1 antagonist SCH 23390, high doses of apomorphine showed higher PE response, while D-2 antagonist sulpiride pretreatment decreased the response of the low doses of the drug. 5. The inhibitory effect of sulpiride was dose-dependent. 6. The D-2 agonists bromocriptine or quinpirole induced a dose-dependent PE. 7. The effects of both drugs were decreased by sulpiride or SKF 38393 pretreatment. 8. Cholinergic drugs physostigmine and neostigmine did not induce PE, but antimuscarinic agent atropine decreased the effects of apomorphine, bromocriptine or quinpirole. 9. It is concluded that D-2 dopamine receptor stimulation may induce PE, while D-1 activation elicit an opposite effect. 10. However, cholinergic stimulation is not able to induce PE, cholinergic inhibition may decrease the PE induced by dopaminergic agents.
Department of Pharmacology, Medical Faculty, University of Tehran, Iran.
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Zarrindast
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Shokravi
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Samini
D000818:Animals; D001058:Apomorphine / Q000494:pharmacology; D001971:Bromocriptine / Q000494:pharmacology; D015259:Dopamine Agents / Q000494:pharmacology*; D018492:Dopamine Antagonists; D065127:Dopamine D2 Receptor Antagonists; D004873:Ergolines / Q000494:pharmacology; D008297:Male; D010276:Parasympatholytics / Q000494:pharmacology; D010277:Parasympathomimetics / Q000494:pharmacology; D010410:Penile Erection / Q000187:drug effects*; D019257:Quinpirole; D051381:Rats; D011954:Receptors, Dopamine / Q000187:drug effects*; D017447:Receptors, Dopamine D1 / Q000037:antagonists & inhibitors / Q000187:drug effects; D017448:Receptors, Dopamine D2 / Q000187:drug effects
D015259:Dopamine Agents; D018492:Dopamine Antagonists; D065127:Dopamine D2 Receptor Antagonists; D004873:Ergolines; D010276:Parasympatholytics; D010277:Parasympathomimetics; D011954:Receptors, Dopamine; D017447:Receptors, Dopamine D1; D017448:Receptors, Dopamine D2; D019257:Quinpirole; D001971:Bromocriptine; D001058:Apomorphine