Figure 2.

Effects of different µ-conotoxins on isometric twitch tension elicited by direct electrical stimulation of isolated mouse EDL muscles. (A) Effects of µ-conotoxins on skeletal muscle contraction. Contractions evoked by direct muscle stimulation and recorded in the absence and presence of 0.1 µM µ-conotoxins. Scale bars: 0.2 g (vertical) and 0.1 s (horizontal). (B) Concentration–response curves of peptide effects on directly elicited muscle contraction. For each µ-conopeptide concentration, the maximal twitch peak amplitude is expressed relative to its control value as the mean ± SEM of three to six experiments. The theoretical curves were calculated from typical sigmoidal nonlinear regression through data points (correlation coefficient r²≥ 0.948). The µ-conopeptide concentration that inhibited 50% of the twitch tension (IC₅₀) is indicated for each peptide studied.