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

Abstract

. The preparation of a muscle strip of Ascaris lumbricoides for the study of the effect of drugs in vitro is described. . 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. . Muscarine‐like drugs (oxotremorine, methacholine, pilocarpine) had no activity. . 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. . Adrenaline neither stimulated the tissue nor affected the responses to nicotine‐like drugs. . 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. . It is concluded that the cholinoceptor in muscle preparations of Ascaris lumbricoides is pharmacologically similar to that of the mammalian autonomic ganglion.

Levamisole‐activated single‐channel currents from muscle of the nematode parasite Ascaris suum

“…The acetylcholine receptors of Ascaris muscle have been classified as nicotinic, as nicotinic agonists produce contractions antagonised by tubocurarine, whereas muscarinic agonists and antagonists have little effect on this preparation (Natoff, 1969;Rozkova et al, 1980;Martin, 1982, Colquhoun et al, 1991. The pharmacology of the acetycholine receptors on Ascaris muscle is most like that of the nicotinic ganglionic receptors of vertebrates, most notably mecamylamine is a potent antagonist at both receptor sites (Natoff, 1969;Rozkova et al, 1980).…”

“…The pharmacology of the acetycholine receptors on Ascaris muscle is most like that of the nicotinic ganglionic receptors of vertebrates, most notably mecamylamine is a potent antagonist at both receptor sites (Natoff, 1969;Rozkova et al, 1980).…”

Studies on chemotherapy of parasitic helminths (VI) Effects of various neuropharmacological agents on the motility of Dipylidium Caninum.

“…On the other hand, the cholinergic mechanism in nematodes such as A. suum (28,29) and A. cantonensis (26) is suggested to be nicotinic from the results on both cholinergic agonists and antagonists. Thus, differences between the natures of the cholinoceptors of nemathelminth and plathelminth may give an explanation for less susceptibility to drugs such as pyrantel which affect nematodes through its ACh-like action (30 …”

Activation and cooperative multi‐ion block of single nicotinic‐acetylcholine channel currents of Ascaris muscle by the tetrahydropyrimidine anthelmintic, morantel

“…The somatic muscle cells which line the body wall of the nematode parasite Ascaris suum have been shown to contract in response to acetylcholine (Baldwin & Moyle, 1949;Natoff, 1969). The contraction is associated with a depolarization of the muscle cells (Del Castillo et al, 1963), which is mediated by a ligand-gated, non-selective cation channel (Martin, 1982;Harrow & Gration, 1985;.…”