Fig. 1. The atrial action potential (AP) from isolated rainbow trout myocytes. AP waveforms were elicited by current-clamp at a rate that corresponded to the heart rate for rainbow trout in vivo at each temperature (0.6 Hz at 7°C, 1.0 Hz at 14°C and 1.4 Hz at 21°C). The steady-state APs from 6-10 cells at each temperature were averaged, and the resultant waveforms were used to stimulate L-type Ca²⁺ channel current (I_Ca) and sarcoplasmic reticulum (SR) Ca²⁺ accumulation in subsequent experiments where the inter-pulse holding level was -80 mV.