Effects of 5mM picrotoxin on the strength-duration curve of the mechanical threshold were examined in frog skeletal muscle fibers in Ringer solution with tetrodotoxin using a point-voltage clamp method. Picrotoxin increased about ten times the efficiency of the electrical quantity i.e., the voltage and duration product above rheobasic mechanical threshold, needed for the short depolarizing pulses, corresponding to the duration of action potentials, to reach mechanical threshold
