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Fig. 7 Effects of heat on AP and resting membrane potential in current-clamped adult zebrafish skeletal muscle fibers. (A) Changes of AP induced by warming of the external solution. The two first and the two last AP in a 0.5-s 50-Hz train of APs are presented at 20 and 37 °C in the same fiber after re-establishing the resting potential at −100 mV at 37 °C. (B) Depolarization of the resting membrane potential and reduction in the voltage change induced by a 50-ms current step of −2 nA at 20° C and 37 °C in the same fiber before re-establishing the resting potential at −100 mV at 37 °C (Left). Histogram showing mean voltage change induced by negative current step (Left axis) and mean resting membrane potential (Right axis) at 20 °C and 37 °C in seven fibers (Right). (C) Superimposition of the first AP of the train shown in A at 20 °C and 37 °C on an expanded scale (Left). Histogram showing mean change in AP amplitude and mean elapsed time between AP peak and 50% or 75% repolarization induced by heat in the same fibers (n = 7) (Right).