Supersensitivity to morphine after chronic sympathetic denervation in guinea-pig colon.
The possible role of opioid systems in the adaptive changes which follow chronic sympathetic denervation in the guinea-pig colon has been studied by comparing the effects of the opioid agonist morphine in control animals and after chronic sympathetic denervation. Supersensitivity to the inhibitory effects of morphine on the peristaltic reflex was observed after chronic sympathetic denervation, while the potency against acetylcholine release was unmodified. Our results suggest that a modification of the opioid system occurs after sympathetic denervation in the guinea-pig colon. Supersensitivity to endogenous opioids at a site different from that regulating acetylcholine release could account for the counter-regulation of intestinal motility after chronic sympathetic denervation.
Department of Internal Medicine and Therapeutics, University of Pavia, 2nd Faculty of Medicine, Varese, Italy.
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F
Marino
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M
Marcoli
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Lecchini
G M
GM
Frigo
D000109:Acetylcholine / Q000032:analysis; D000818:Animals; D003106:Colon / Q000187:drug effects / Q000294:innervation*; D003714:Denervation; D004305:Dose-Response Relationship, Drug; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D010528:Peristalsis / Q000187:drug effects; D013564:Sympathetic Nervous System / Q000187:drug effects / Q000502:physiology*
D009020:Morphine; D000109:Acetylcholine