The pharmacology of the cholinoceptor in muscle preparations of Ascaris lumbricoides var. suum

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Abstract
1 . The preparation of a muscle strip of Ascaris lumbricoides for the study of the effect of drugs in vitro is described. 2 . Stimulant drugs which are classified as nicotine-like in mammalian pharmacology increased the isometric tension of this preparation. These drugs were, in descending order of potency: dimethylphenylpiperazinium, nicotine, acetylcholine, carbachol, decamethonium and pyridine-2-aldoxime methiodide. 3 . Muscarine-like drugs (oxotremorine, methacholine, pilocarpine) had no activity. 4 . Potassium and barium ions stimulated the tissue, while the anti-cholin-esterases, dichlorvos and eserine, increased the resting tension of the preparation and potentiated the responses to acetylcholine. 5 . Adrenaline neither stimulated the tissue nor affected the responses to nicotine-like drugs. 6 . The relative potency of several blocking agents which antagonize the responses to nicotine-like drugs was assayed. These blocking agents were, in descending order of potency: mecamylamine, (+)-tubocurarine, hexamethonium, atropine and piperazine. Acetylcholine, dimethylphenylpiperazinium and pyridine-2-aldoxime methiodide apparently act on a common receptor, for each blocking agent had a similar molar inhibitory concentration against these stimulants. 7 . It is concluded that the cholinoceptor in muscle preparations of Ascaris lumbricoides is pharmacologically similar to that of the mammalian autonomic ganglion.