Shinozaki H, Ishida M
Brain Res. 1985 May 13;334(1):33-40. doi: 10.1016/0006-8993(85)90564-5.
At the crayfish neuromuscular junction, tuberostemonine, an alkaloid from Stemona japonica, reduced the amplitude of both the excitatory junctional potential (e.j.p.) and the glutamate response in a dose-dependent manner at concentrations above 0.1 mM. Tuberostemonine acted presynaptically on the crayfish neuromuscular junction to reduce a quantal content of extracellularly recorded e.j.p.s, and postsynaptically to reduce their unit size. The decay of the excitatory synaptic current was accelerated by tuberostemonine. The gradual decline of the successive glutamate currents induced by a train was facilitated by the presence of tuberostemonine even in the muscle fibre pre-treated with concanavalin A. The rate of recovery from the refractory form of the glutamate receptor to the free reactive one was slightly affected by tuberostemonine when it was determined by using a paired pulse method. The inhibitory action of tuberostemonine on glutamate responses was voltage-dependent and hyperpolarization increased the drug action. These results indicate that tuberostemonine acts in part as an open-channel blocker at the crayfish neuromuscular junction.
在小龙虾神经肌肉接头处，百部生物碱（一种来自日本百部的生物碱）在浓度高于0.1 mM时，以剂量依赖的方式降低兴奋性接头电位（e.j.p.）的幅度和谷氨酸反应。百部生物碱在突触前作用于小龙虾神经肌肉接头，以减少细胞外记录的e.j.p.s的量子含量，并在突触后作用以减小其单位大小。百部生物碱加速了兴奋性突触电流的衰减。即使在用伴刀豆球蛋白A预处理的肌纤维中，百部生物碱的存在也促进了由一串刺激诱导的连续谷氨酸电流的逐渐下降。当使用配对脉冲法测定时，百部生物碱对谷氨酸受体从不应期形式恢复到游离反应性形式的恢复速率有轻微影响。百部生物碱对谷氨酸反应的抑制作用是电压依赖性的，超极化会增强药物作用。这些结果表明，百部生物碱在小龙虾神经肌肉接头处部分作为开放通道阻滞剂起作用。
