The effect of ammodytin L on frog neuromuscular junction

Effects of myotoxic ammodytin L on frog neuromuscular junction were examined by morphological, enzymatic and electrophysiological studies. Electron micrographs of the frog neuromuscular junction revealed destruction of muscle fibers. Nerve terminals seemed to remain intact. The activity of the muscle specific enzymes in the bathing solution rose with time in a dose-dependent manner. Ammodytin L depressed the response of the neuromuscular preparation to acetylcholine. Measurements of electrically triggered isometric muscle contractions show that the toxin depresses the neuromuscular transmission both in the curarised and in the untreated frog neuromuscular preparation with marked difference between the time-courses of both effects, indicating that neurotoxic effect may also be involved.