Morphine inhibits dopaminergic and cholinergic induced ejaculation in rats.
1. Subcutaneous injection (s.c.) of apomorphine (0.1-0.5 mg/kg) and intraperitoneal administration (i.p.) of quinpirole (0.01-0.25 mg/kg), physostigmine (0.05-0.2 mg/kg) and pilocarpine (0.75-3 mg/kg, i.p.) but not neostigmine (0.1-1 mg/kg) induced ejaculation in rats. 2. The responses of drugs were reduced by morphine (1-6 mg/kg, s.c.) pretreatment. 3. The inhibitory effect of morphine was reversed by naloxone (1.5 mg/kg, s.c.). 4. Naloxone (0.75-3 mg/kg, s.c.) alone induced slight but significant ejaculation. 5. Ejaculatory responses induced by apomorphine and quinpirole but not those by physostigmine and pilocarpine were reduced by sulpiride (100 mg/kg, i.p.) pretreatment. 6. Domperidone (1-30 mg/kg, i.p.) did not change the response induced by apomorphine. 7. Pretreatment of animals with the cholinergic antagonist atropine (10 mg/kg, i.p.) decreased the frequency of ejaculation induced by apomorphine, quinpirole, physostigmine or pilocarpine. 8. It may be concluded that D-2 activation induces ejaculation through influence on cholinergic mechanisms and morphine inhibits the ejaculation induced by activation of both cholinergic and dopaminergic systems via opiate receptor sites.
Department of Pharmacology, School of Medicine, University of Medical Sciences, Tehran, Iran.
M R
MR
Zarrindast
S M
SM
Mamanpush
A
A
Rashidy-Pour
D000818:Animals; D001058:Apomorphine / Q000494:pharmacology; D001285:Atropine / Q000494:pharmacology; D018678:Cholinergic Agents / Q000494:pharmacology*; D015259:Dopamine Agents / Q000494:pharmacology*; D004542:Ejaculation / Q000187:drug effects*; D004873:Ergolines / Q000494:pharmacology; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D009270:Naloxone / Q000494:pharmacology; D010830:Physostigmine / Q000494:pharmacology; D010862:Pilocarpine / Q000494:pharmacology; D019257:Quinpirole; D051381:Rats; D013469:Sulpiride / Q000494:pharmacology
D018678:Cholinergic Agents; D015259:Dopamine Agents; D004873:Ergolines; D010862:Pilocarpine; D019257:Quinpirole; D009270:Naloxone; D009020:Morphine; D001285:Atropine; D013469:Sulpiride; D010830:Physostigmine; D001058:Apomorphine