Effects of opioid and alpha 2-adrenoceptor agonists on the isolated ileum of morphine-dependent guinea-pigs during withdrawal and after clonidine treatment.
The present study was undertaken to investigate the effect of clonidine administration to opiate-dependent guinea-pigs after morphine withdrawal on subsequent twitch responses of the longitudinal muscle-myenteric plexus preparations to electrical field stimulation. The results indicate that clonidine, administered immediately after morphine removal, causes tolerance to the inhibition exerted by opioid and alpha 2-adrenoceptor agonists on the electrically-evoked twitches. Such a finding suggests that the mechanism of action of clonidine involves not only its well-known effects on locus coeruleus neurons but also that it has specific actions on the myenteric plexus. This work shows the existence of interactions between opioid and alpha 2-adrenoceptor on the cholinergic neurons present in the isolated ileum.
Colado
M I
MI
Departamento de Farmacología, Facultad de Medicina, Universidad Complutense de Madrid, Spain.
Martin
M I
MI
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000818:Animals; D003000:Clonidine / Q000008:administration & dosage / Q000494:pharmacology*; D004361:Drug Tolerance; D004558:Electric Stimulation; D006168:Guinea Pigs; D007082:Ileum / Q000187:drug effects / Q000294:innervation*; D008297:Male; D009020:Morphine / Q000494:pharmacology; D009021:Morphine Dependence / Q000503:physiopathology*; D009197:Myenteric Plexus; D009270:Naloxone / Q000494:pharmacology; D009294:Narcotics / Q000494:pharmacology; D009469:Neuromuscular Junction / Q000187:drug effects* / Q000503:physiopathology; D013375:Substance Withdrawal Syndrome / Q000503:physiopathology; D015016:Yohimbine / Q000494:pharmacology
D000316:Adrenergic alpha-Agonists; D009294:Narcotics; D015016:Yohimbine; D009270:Naloxone; D009020:Morphine; D003000:Clonidine