Effects of adenosine analogues on apomorphine-induced penile erection in rats.
1. In the present work, the effect of adenosine agonists and antagonists on apomorphine-induced penile erection (PE) has been studied. 2. Subcutaneous (s.c.) injection of the nonselective D1/D2 dopamine receptor agonist apomorphine (0.05-0.5 mg/kg) induced PE in a biphasic manner. The maximum effect was obtained with 0.1 mg/kg of the drug. The response decreased with increasing doses of apomorphine, from 0.1 to 0.5 mg/kg. 3. Intraperitoneal (i.p.) injections of adenosine agonists 5'-N-ethylcarboxamidoadenosine (NECA) and N6-cyclohexyladenosine (CHA) decreased the response of apomorphine. Apomorphine-induced PE was increased by low doses (25, 50 mg/kg, i.p.) and decreased by high doses (75, 100 mg/kg, i.p.) of the adenosine antagonist theophylline, respectively. Inhibition of PE induced by NECA and CHA was antagonized by 8-PT pretreatment. 4. Intracerebroventricular (i.c.v.) administration of CHA, NECA, and theophylline produced the same effects as i.p. injections of these agents on PE responses. It is concluded that A-1 and A-2 adenosine receptor activation may inhibit PE induced by dopaminergic mechanism(s), which can be prevented by 8-PT pretreatment.
Sharifzadeh
M
M
Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, Iran.
Zarrindast
M R
MR
Samini
M
M
D000241:Adenosine / Q000031:analogs & derivatives / Q000494:pharmacology; D019830:Adenosine-5'-(N-ethylcarboxamide); D000818:Animals; D001058:Apomorphine / Q000494:pharmacology*; D008297:Male; D010410:Penile Erection / Q000187:drug effects*; D051381:Rats; D018047:Receptors, Purinergic P1 / Q000187:drug effects* / Q000502:physiology; D013806:Theophylline / Q000031:analogs & derivatives / Q000494:pharmacology
D018047:Receptors, Purinergic P1; D019830:Adenosine-5'-(N-ethylcarboxamide); C027513:N(6)-cyclohexyladenosine; D013806:Theophylline; C028322:8-phenyltheophylline; D000241:Adenosine; D001058:Apomorphine