|
|
|
|
|
|
|
|
|
|
T.A. Day, N. Orr, J.L. Bennett and R.A. Pax
Parasitology 106:471-477
Three morphologically distinct types of muscle fibres isolated from the phatyhelminth Schistosoma mansoni have been studied with whole cell current- and voltage-clamp techniques. Fibres showed a marked time-dependent decrease in membrane resistance in response to depolarizing current injections. Voltage-clamp experiments revealed the presence of two distinct voltage-gated outward currents. The most prominent current is a slowly activating, slowly and incompletely inactivating potassium current similar to delayed rectifier currents which have been described in a variety of cell types from a variety of organisms. Also present is a faster activating, quickly and completely inactivating potassium current that shares functional characteristics with ‘A' currents. All three of the cell types studied possess a delayed recifier current, but only two of the three types have ‘A'-currents. Though depolarization with high K+ leads to contraction of the dispersed fibres, no voltage-grated inward currents could be detected by whole cell voltage-clamp under any of our conditions.