Influences of dopamine agonists and antagonists of baclofen antinociception in mice.
The effects of dopamine agonists and antagonists on baclofen antinociception were examined in mice using the tail-flick test. Injection of different doses of baclofen (5-10 mg/kg, i.p.) produced dose-related antinociception. This effect was decreased in animals treated with SKF 38393 (8 mg/kg, i.p.) or apomorphine (2 mg/kg, s.c.). The inhibitory responses of both SKF 38393 and apomorphine were decreased in animals pretreated with SCH 23390 (0.1 mg/kg, s.c.). Bromocriptine (1 mg/kg, i.p.), or lower doses of apomorphine (0.1 mg/kg, s.c.), did not alter the baclofen-induced antinociception. Antinociception induced by baclofen (5-10 mg/kg, i.p.) was decreased in animals pretreated with sulpiride (10 mg/kg, i.p.) but not by SCH 23390 (0.1 mg/kg, s.c.). Administration of apomorphine, SKF 38393, bromocriptine or sulpiride alone did not change the latency in the tail-flick test, but SCH 23390 induced a slight but significant antinociception. On the basis of the above findings, it may be concluded that D-1 receptor activation can decrease the baclofen antinociceptive effect.
Department of Pharmacology, Medical Faculty, University of Tehran, Iran.
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Zarrindast
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Moghaddampour
D000700:Analgesics; D000818:Animals; D001058:Apomorphine / Q000494:pharmacology; D001418:Baclofen / Q000494:pharmacology*; D001552:Benzazepines / Q000494:pharmacology; D015259:Dopamine Agents / Q000494:pharmacology*; D018492:Dopamine Antagonists; D004305:Dose-Response Relationship, Drug; D006220:Haloperidol / Q000494:pharmacology; D007274:Injections, Intraperitoneal; D008297:Male; D051379:Mice; D010646:Phentolamine / Q000494:pharmacology; D011930:Reaction Time / Q000187:drug effects; D011954:Receptors, Dopamine / Q000502:physiology; D017447:Receptors, Dopamine D1; D017448:Receptors, Dopamine D2
D000700:Analgesics; D001552:Benzazepines; D015259:Dopamine Agents; D018492:Dopamine Antagonists; D011954:Receptors, Dopamine; D017447:Receptors, Dopamine D1; D017448:Receptors, Dopamine D2; D001418:Baclofen; D006220:Haloperidol; D001058:Apomorphine; D010646:Phentolamine