AbstractDecreasing the temperature from 37 C to 20 C in vitro reactivates muscle twitch in response to nerve stimulation in a muscle previously paralyzed by botulinum toxin. Transmitter release calculated as quantum content of endplate potentials has an extremely enhanced sensitivity to temperature in botulinum paralysis (Q10about 45) compared to normal muscle blocked by high magnesium concentration (Q10about 2). This difference is not caused by increased efficacy of the calcium mechanism of transmitter release in botulinum poisoning at low temperature, as demonstrated by unaltered calcium‐dependence of quantum content at 22 C compared to 35 C for both types of neuromuscular block. The results give exciting clues to the mode of action of botulinum toxi