Different influences of adenosine receptor agonists and antagonists on morphine antinociception in mice.
1. Subcutaneous (s.c.) administration of morphine to mice induced a dose-dependent antinociception. 2. Pretreatment of animals with adenosine receptor antagonists NECA (5'-N-ethylcarboxamide-adenosine) and L-PIA (N6-phenylisopropyladenosine) potentiated, while adenosine agonist CHA (N6-cyclohexyladenosine) decreased the morphine response. 3. Adenosine antagonist theophylline decreased, but adenosine receptor antagonist 8-PT (8-phenyltheophylline) increased the antinociception effect of morphine. Inhibitory effect of CHA on morphine antinociception was also reversed by 8-PT pretreatment. 4. NECA or L-PIA induced a high degree of antinociceptive effect in animals pretreated with 8-PT. 5. Dipyridamole pretreatment did not alter the effect of morphine. 6. It is concluded that A-1 and/or A-2 adenosine receptors are involved in morphine antinociception and the adenosine mechanism(s) may exert a modulatory role in this respect.
Department of Pharmacology, School of Medicine, University of Tehran, Iran.
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Zarrindast
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Nikfar
D000241:Adenosine / Q000031:analogs & derivatives / Q000494:pharmacology; D019830:Adenosine-5'-(N-ethylcarboxamide); D000818:Animals; D004176:Dipyridamole / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D008297:Male; D051379:Mice; D009020:Morphine / Q000494:pharmacology*; D009619:Nociceptors / Q000187:drug effects*; D010660:Phenylisopropyladenosine / Q000494:pharmacology; D058915:Purinergic P1 Receptor Antagonists; D058919:Purinergic P2 Receptor Antagonists; D018047:Receptors, Purinergic P1 / Q000502:physiology*; D018048:Receptors, Purinergic P2 / Q000502:physiology*; D013623:Tail / Q000187:drug effects / Q000502:physiology; D013806:Theophylline / Q000031:analogs & derivatives / Q000494:pharmacology
D058915:Purinergic P1 Receptor Antagonists; D058919:Purinergic P2 Receptor Antagonists; D018047:Receptors, Purinergic P1; D018048:Receptors, Purinergic P2; D010660:Phenylisopropyladenosine; D019830:Adenosine-5'-(N-ethylcarboxamide); C027513:N(6)-cyclohexyladenosine; D004176:Dipyridamole; D009020:Morphine; D013806:Theophylline; C028322:8-phenyltheophylline; D000241:Adenosine