Effects of ammodytin L on miniature and endplate potentials in neuromuscular junction of frog m. cutaneus pectoris

Neurotoxic effects of ammodytin L (AtnL), a potent phospholipase Az homolog ue, was studied in hog neuromuscular preparation m. cutaneus pectoris by me asuring the influence of the toxin on the amplitude and the frequency of mi niature and endplate potentials (MEPPs, EPPs). AtnL, in 100 nM concentratio n, significantly increases spontaneous quantal acetylcholine release from t he motor nerve endings, observed as the increase in MEPPs frequency. At 100 nM or higher concentration the toxin decreases EPPs amplitude and the memb rane potential (MP) simultaneously. No significant effect of AtnL on EPPs w as observed at any concentration bellow 100 nM. Our results indicate that i n hog AtnL shows the typical myotoxic effects, but it also exerts presynapt ic effects.