Frequency-dependent neuromuscular blockade by textilotoxin in vivo.

The effect of stimulation frequency on the timecourse of neuromuscular blockade, following the administration of textilotoxin (20 micrograms/kg) or beta-bungarotoxin (50 micrograms/kg), was examined in the interdigital muscles of the hindlimb in anaesthetized mice. While the time of death was variable, neuromuscular blockade of the interdigital muscles occurred at the same time as respiratory failure with both textilotoxin and beta-bungarotoxin only at stimulation rates of 0.5 Hz and above. Textilotoxin (50 micrograms/kg) produced an increase in the heart rate prior to death but no change in the shape of the electrocardiogram.