Schistosoma mansoni: Characterization of the electrical potential from the tegument of adult males

The tegumental membrane potential appears to be dependent primarily on the K+ gradient across the surface since a 10-fold increase in external K+ causes a 30-mV change in the potential.

Abstract

An electrical potential having a value of −35 mV (SD = 7.4) is recorded upon penetration of the ventral surface of adult male Schistosoma mansoni with a microelectrode. Histological studies using horseradish peroxidase as a marker injected iontophoretically through the recording electrode indicate that this potential originates in the tegumental epithelium. Recordings from animals with contractile activity showed spontaneous nonovershooting depolarizations with durations of 20 to 100 msec and amplitudes between 5 and 15 mV. Slow-wave depolarizations are also observed and are most frequent in animals showing only slight movement. The tegumental membrane potential appears to be dependent primarily on the K+ gradient across the surface since a 10-fold increase in external K+ causes a 30-mV change in the potential. Altering the external concentration of Cl− has little effect on the tegumental potential, but lowering the external Na+ concentration to 37 mM causes a 10-mV depolarization. Praziquantel (PZ) has little initial effect on the tegumental membrane potential. A slow depolarization does occur, however, which reaches a significant level about 10 min after PZ (1 μM). Carbachol and dopamine are without significant effects on the tegumental membrane potential.