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T.A. Day, G.Z. Chen, C.L. Miller, M. Tian, J.L. Bennett and R.A. Pax
Parasitology 113:55-61
Cholinergic compounds inhibit FMRFamide-induced contractions
in dispersed muscle fibres isolated from adult Schistosoma mansoni.
Acetylcholine (ACh) was the most effective cholinergic agonist
tested with an EC(50) < 100 nM. Less effective were propionylcholine
and arecoline with EC(50) < 1 uM and butyrylcholine and carbachol
with EC(50) < 10 uM. Choline, muscarine, pilocarpine, nicotine,
DMPP (1,1-dimethylphenylpiperazine) and levamisole were all ineffective.
Amongst tested antagonists, d-tubocurarine (100 uM), mecamylamine
(1 mM), atropine (1 mM), scopolamine (1 mM) and quinuclidinyl
benzilate (10 uM) were all ineffective. Bicuculline, picrotoxin
and strychnine were also ineffective. However alpha-bungarotoxin,
at 100 nM, was able to block the inhibitory ACh effect. From these
data it appears that the cholinergic receptor on the schistosome
muscle fibres may be of the nicotinic type, but that its pharmacology
is different from that of nicotinic receptors of vertebrates as
well as of nematodes or a variety of other invertebrates.