吡喹酮对神经肌肉接头传递的作用

吡喹酮可使电刺激腓总神经所引起的胫前肌收缩反应明显加强。如给腓总神经施加超强刺激,静脉注射筒箭毒碱可减弱肌肉收缩反应,吡喹酮却能加强筒箭毒碱的抑制作用,使神经肌肉传递迅即完全阻断。采用微电极细胞内记录技术研究吡喹酮对离体大鼠膈神经隔肌的作用,发现吡喹酮不明显影响膈肌细胞的静息膜电位。低浓度吡喹酮(2×10^-4M)可使微终板电位(mepp)频率明显增加。高浓度吡喹酮8×10^-4M则使mepp振幅逐渐变小和消失。吡喹酮在使神经肌肉传递阻滞不断加深的同时,尚能使终板电位的振幅变小,终致完全消失。

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.