Surface electrical activity from Schistosoma mansoni: a sensitive measure of drug action.

Spontaneous electrical activity was recorded by means of suction electrodes placed on the surface of adult, male Schistosoma mansoni. This electrical activity was a complex of bi- and triphasic potentials that ranged from smaller amplitude waves (0-40 microV) of high frequency (10-40/sec), to randomly occurring, larger amplitude waves (40-1,000+ microV) of lower frequency (0-5/sec). Many of the larger potentials (greater than 100 microV) appeared to be propagated. This activity varied with respect to the region of the parasite. The caudal region consistently exhibited potentials greater than 120 microV, whereas activity in the anterior region was rarely greater than 40 microV. Decreased concentrations of Ca++ (0.0 or 0.14 mM), an increased concentration of Mg++ (30.0 mM) or addition of a mM CoCl2 significantly decreased the level of electrical activity. Drug concentrations of 1 x 10(8) M carbachol, 1 x 10(-6) M metrifonate, 1 x 10(-8) dopamine, and 1 x 10(-5) M pentobarbital also significantly decreased electrical activity. In contrast, serotonin (1 x 10(-7) M) significantly increased the level of electrical activity.