Fig. 2. The effect of temperature on intracellular Ca²⁺ concentration ([Ca²⁺]_i) and L-type Ca²⁺ channel current (I_Ca) in trout atrial myocytes. (A) The effect of temperature on [Ca²⁺]_i during SQ_0.2Hz, SQ_physiol and AP_physiol (the physiological frequencies were: 0.6 Hz at 7°C, 1.0 Hz at 14°C and 1.4 Hz at 21°C). The increase in the resting level of the transient at SQ_physiol reflects the increase in diastolic Ca²⁺ concentration (see Fig. 4, Table 3). (B) Current recordings of I_Ca under the same conditions. Peak current amplitude was calculated as the difference between the peak inward current and the current recorded at the end of the depolarizing pulse. The currents elicited at SQ_0.2Hz were leakage corrected using the P/N procedure of the software (Clampex, Axon Instruments). Leakage correction was not employed at SQ_physiol or AP_physiol. Mean data and statistical analysis is given in Tables 1,2,3 and in Fig. 3. SQ_0.2Hz, square pulses at a frequency of 0.2 Hz; SQ_physiol, square pulses at physiological frequency; AP_physiol, action potential at physiological frequency.

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