EFFECTS OF PRAZIQUANTEL ON THE NEUROMUSCULAR TRANSMISSION

The effects of praziquantel, a new schistosomicide, on the neuromuscular transmission were studied on anterior tibial muscle of anesthetized rabbits and isolated rat phrenic nerve diaphragm preparations.Results showed that praziquantel (10～80 mg/kg) had a stimulatory action on the twitch of anterior tibial muscle elicited by electrical stimulation of the common peroneal nerve. The contractile response of anterior tibial muscles was increased in relation to the dosage of praziquantel. In this preparation, the neuromuscular blocking action of tubocurarine was significantly enhanced by praziquantel and antagonized by neostigmine.By the technique of glass microelectrode for intracellular recording, the changes of electrical properties of neuromuscular junction were observed on isolated rat phrenic nerve-diaphragm. Praziquantel did not significantly affect the resting membrane potential of muscle cells. In lower concentration (2×10^-4 M), it increased the frequency of miniature end-plate potential (mepp), and, in higher concentration (8×10^-4M), decreased the amplitude of mepp. Praziquantel (8×10^-4 M) also inhibited the endplate potential (epp).In conclusion, praziquantel has both presynaptic and postsynaptic action on the neuromuscular transmission. It might promote the release of acetylcholine from nerve endings and produce excitation of neuromuscular junction. It might also reduce the sensitivity of the postsynaptic receptor to acetylcholine and result in neuromuscular blockade.