title: Opiate tolerance/dependence in the isolated guinea pig ileum is associated with an increased sensitivity to acetylcholine.
abstract: The number of rhythmic circular muscle contractions elicited by acetylcholine was increased in isolated intestinal segments taken from morphine-tolerant/dependent guinea pigs and exposed in vitro to an adequate normorphine concentration. Segments which underwent a partial withdrawal in vitro showed some degree of supersensitivity to acetylcholine which was, however, not significant. In contrast, basal peristaltic reflex activity was enhanced during a partial opiate withdrawal but not during exposure of the segments to a normorphine concentration high enough to maintain opiate tolerance/dependence. These data suggest that a supersensitivity to acetylcholine participates, at least partially, in the development of tolerance to the inhibitory action of opioids upon intestinal peristalsis.
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology*; D000818:Animals; D004361:Drug Tolerance; D006168:Guinea Pigs; D006801:Humans; D007082:Ileum / Q000187:drug effects* / Q000503:physiopathology; D008297:Male; D009021:Morphine Dependence / Q000503:physiopathology*; D009130:Muscle, Smooth / Q000503:physiopathology; D010528:Peristalsis / Q000187:drug effects
chemical_list: D000109:Acetylcholine