Surface Electrical Activity from Schistosoma mansoni: A Sensitive Measure of Drug Action

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Abstract
Spontaneous electrical activity was recorded by means of suction electrodes placed on the surface of adult, male S. mansoni. This electrical activity was a complex of bi- and triphasic potentials that ranged from smaller amplitude waves (0-40.mu.V) of high frequency (10-40/s), to randomly occurring, larger amplitude waves (40-1000 + .mu.V) of lower frequency (0-5/s). Many of the larger potentials (> 100 .mu.V) appeared to be propagated. This activity varied with respect to the region of the parasite. The caudal region consistently exhibited potentials > 120 .mu.V, whereas activity in the anterior region was rarely greater than 40 .mu.V. Decreased concentrations of Ca2+ (0.0 or 0.14 mM), an increased concentration of Mg2+ (30.0 mM) or addition of 1 mM CoCl2 significantly decreased the level of electrical activity. Drug concentrations of 1 .times. 10-8 M carbachol, 1 .times. 10-6 M metrifonate, 1 .times. 10-8 M dopamine and 1 .times. 10-5 M pentobarbital also significantly decreased electrical activity. Serotonin (1 .times. 10-7 M) significantly increased the level of electrical activity.