Schistosoma mansoni: Neurotransmitters, longitudinal musculature and effects of electrical stimulation

Longitudinal muscle shortening of adult male Schistosoma mansoni is produced by electrical stimulation. Responses are frequency and strength dependent. Neither 5-hydroxytryptamine (5-HT) antagonists nor dopamine interfere with the response. 5-HT does not enhance it. Carbachol (10 −4 M), eserine (10 −6 M), and metrifonate (10 −5 M) block the response but acetylcholine alone has no affect. Atropine (10 −4 M) partially counteracts the effects of carbachol. Hyperosmotic sucrose but not urea blocks the stimulation response. It is concluded that the response is nonneuronally conducted via a pathway involving gap junctions and that neurotransmitters probably act as modulators of motor activity rather than as initiators of it.