In vitro effects of various neuropharmacological agents on the motility of adult Clonorchis sinensis.

Stimulatory effects were observed in vitro when 5-HT was applied to whole worm preparations of Clonorchis sinensis. The stimulatory action of 5-HT was antagonized by tryptophol, clomipramine and imipramine. Strychnine remarkably stimulated motility. The action of strychnine was enhanced by 5-HT but inhibited by tryptophol. GABA, Phenylephrine, isoproterenol, dibenamine and phentolamine showed little influence on motility. Inhibitory effects were caused by eserine, arecoline, carbachol, DMPP and hemicholinium-3, but not by ACh, pilocarpine and McN-A-343. The inhibitory actions of eserine or carbachol were not antagonized by d-tubocurarine, hexamethonium or atropine. These results suggest that in regulating the motility of C. sinensis ACh may function as an inhibitory neurotransmitter and 5-HT as an excitatory transmitter in a manner similar to that already established for other trematodes such as Fasciola hepatica and Schistosoma mansoni.