Morphine attenuates cholinergic nerve activity in human isolated colonic muscle.
The action of morphine on cholinergic nerves in human sigmoid taenia coli muscle strips (taenia) was investigated using a radiolabelling technique. Basal release of tritiated material from taenia was increased by electrical field stimulation (EFS). This increase was tetrodotoxin (3.14 microM)-sensitive and calcium-dependent. Analysis of basal and stimulated release of tritiated material indicated that evoked release (i.e. stimulated minus basal) is almost entirely due to an increase in [3H]-acetylcholine ([3H]-ACh) output. Evoked release of [3H]-ACh was dependent on the current strength and could be greatly reduced by exposing taenia to hemicholinium (34.8, 87.0 microM) before and during incubation with [3H]-choline (4 microCi ml-1, 15 Ci mmol-1). Spontaneous activity, muscle tone and the motor response of taenia to EFS were unaffected by morphine. Evoked, but not basal, release of tritiated material was inhibited by morphine (1.32-13.20 microM) in a concentration-dependent manner. The inhibition of release was frequency-dependent and naloxone (0.28 microM)-sensitive. The possible relationship between the effects of morphine on cholinergic nerves in taenia muscle and its actions in vivo are discussed.
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D003106:Colon / Q000187:drug effects / Q000294:innervation*; D004558:Electric Stimulation; D006426:Hemicholinium 3 / Q000494:pharmacology; D006801:Humans; D066298:In Vitro Techniques; D009020:Morphine / Q000494:pharmacology*; D009046:Motor Neurons / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects*; D018377:Neurotransmitter Agents / Q000378:metabolism; D010275:Parasympathetic Nervous System / Q000187:drug effects*; D013779:Tetrodotoxin / Q000494:pharmacology
D018377:Neurotransmitter Agents; D006426:Hemicholinium 3; D013779:Tetrodotoxin; D009020:Morphine