A benzodiazepine derivative and praziquantel: effects on musculature of Schistosoma mansoni and Schistosoma japonicum.

The benzodiazepine derivative (Ro 11-3128) which has central nervous effects similar to other benzodiazepines, and praziquantel (PZ), are two new antischistosomal drugs. At low concentrations these drugs will produce a marked spastic paralysis of male Schistosoma mansoni musculature. An analysis of the action of these drugs on the parasite's musculature shows that Ro 11-3128 and PZ produced a rapid rise in the tension of the musculature of male schistosomes. Various compounds known to interact with the schistosome's neuroreceptive sites did not block of potentiate the action of these drugs. Removal of Ca2+ or addition of Mg2+ to the incubation medium blocked the action of these drugs on the schistosome's musculature. Uptake studies of inorganic cations by male schistosome's indicate that Ro 11-3128 and PZ decrease the influx of K+ but stimulate the influx of Ca2+ and Na+ into the male schistosome. It is suggested that this interference with inorganic ion transport mechanisms causes the contraction of the schistosome musculature.