Reproducible withdrawal contractions of isolated guinea-pig ileum after brief morphine exposure: effects of clonidine and nifedipine.
Guinea-pig ileum stored for 30 min in Krebs solution and then mounted in Tyrode solution gave reproducible contracture responses to naloxone after brief exposure to morphine. The preparation lasted for several hours and a variety of pharmacological tests could be made. Clonidine, an alpha 2-adrenoceptor agonist, and nifedipine, a calcium channel antagonist, both known to interfere with tolerance and physical dependence, inhibited naloxone withdrawal contractures in a dose related way. Their action seemed to be receptor-mediated since yohimbine and Bay k 8644, respectively, reversed their inhibitory effect.
Institute of Pharmacology and Pharmacognosy, University of Rome La Sapienza, Italy.
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Valeri
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Martinelli
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Morrone
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Severini
D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D003000:Clonidine / Q000494:pharmacology*; D006168:Guinea Pigs; D007082:Ileum / Q000187:drug effects; D066298:In Vitro Techniques; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects*; D009270:Naloxone / Q000494:pharmacology; D009543:Nifedipine / Q000494:pharmacology*; D013375:Substance Withdrawal Syndrome / Q000503:physiopathology*; D015016:Yohimbine / Q000494:pharmacology
D015016:Yohimbine; D009270:Naloxone; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D009020:Morphine; D009543:Nifedipine; D003000:Clonidine; D000109:Acetylcholine