Fig. 4. This figure is an example of a recording for a single myocyte at 21°C. Part (A) shows intracellular Ca²⁺ concentration ([Ca²⁺]_i) and part (B) shows the corresponding L-type Ca²⁺ channel current (I_Ca) at each stimulus change. Each panel is marked according to the frequency and waveform used to elicit currents and transients. The first five transients at each temperature were elicited by square pulses at 0.2 Hz (SQ_0.2Hz). The middle five transients were elicited by SQ pulses applied at a physiologically relevant frequency for the test temperature (SQ_1.4Hz), but with a long pulse duration (500ms). Together these factors contribute to the dramatic rise in diastolic Ca²⁺ levels. The last five transients were elicited by temperature- and frequency-dependent action potentials (AP_1.4Hz). The dotted line in the lower panel indicates 0mV. Leakage correction was employed at SQ_0.2Hz, but not at SQ_1.4Hz or AP_1.4Hz.