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.
Zarrindast
M R
MR
Department of Pharmacology, School of Medicine, University of Medical Sciences, Tehran, Iran.
Mamanpush
S M
SM
Rashidy-Pour
A
A
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