The effect of ammodytin L on frog neuromuscular junction

Effects of myotoxic ammodytin L on frog neuromuscular junction were examine d by morphological, enzymatic and electrophysiological studies. Electron mi crographs of the frog neuromuscular junction revealed destruction of muscle fibers. Nerve terminals seemed to remain intact. The activity of the muscl e specific enzymes in the bathing solution rose with time in a dose-depende nt manner. Ammodytin L depressed the response of the neuromuscular preparat ion to acetylcholine. Measurements of electrically triggered isometric musc le contractions show that the toxin depresses the neuromuscular transmissio n both in the curarised and in the untreated frog neuromuscular preparation with marked difference between the time-courses of both effects, indicatin g that neurotoxic effect may also be involved.