A preliminary investigation of the pharmacology of longitudinal muscle strips from human isolated jejunum

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Abstract
The effects of drugs on longitudinal muscle strips of human jejunum were studied in vitro. The muscarinic site of action of acetylcholine was demonstrated. The sympathomimetic amines phenylephrine, noradrenaline and isoprenaline each produced only a relaxation by an action on adrenergic α- and β-receptors. The presence of both types of receptor was demonstrated by selective adrenergic blockade with pronethalol or Hydergine. The ganglion stimulating agent dimethylphenyl-piperazinium produced a contraction by an action on intramural cholinergic nervous tissue. When the contractile response was blocked by hyoscine, a relaxation occurred, due to the stimulation of an adrenergic mechanism which could be either the sympathetic nerves of the intrinsic nerve plexus or adrenergic stores in the bowel wall. The contraction produced by histamine was not inhibited by hyoscine or hexamethonium but was blocked by mepyramine, thus indicating a direct effect of the drug on the smooth muscle. 5-Hydroxytryptamine produced a contraction by a direct action on the muscle, since the response was not inhibited by hyoscine or hexamethonium but was blocked by methysergide (UML 491).

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