Fig. 1. The amplitudes of EJPs and IJPs vary as a function of temperature. (A) Intracellular recordings from a muscle fiber in which a single EJP and a single IJP are elicited in each stimulus trial over the temperature range 2–18°C. Traces are averaged from ten trials at each temperature; the resting potential (RP) recorded at each temperature is indicated above each trace. In this experiment, the IJP reversed polarity at 6.0°C. (B) Amplitude of EJPs as a function of temperature in nine muscle fibers. Data are normalized to the value measured at 2°C; at this temperature EJP amplitude in these fibers ranged from 1.4 to 12.9 mV. EJPs are depolarizing in polarity over the entire temperature range. (C) Amplitude of IJPs as a function of temperature in six muscle fibers. Data are normalized to values measured at 2°C; at this temperature IJP amplitude in these fibers ranged from –0.1 mV to –5.2 mV. The broken line indicates the reversal of the IJP polarity; data below the broken line represent IJPs of hyperpolarizing polarity. (D) Muscle resting potential (mean ± s.e.m.) measured as a function of temperature in 18 muscle fibers, including those for which data is presented in B and C. (E) Input resistance of muscle fibers (mean ± s.e.m.; N=11) measured in response to hyperpolarizing current pulses. Values are normalized to those measured at 2°C.