Fig. 2. Steady-state activation (m_x) and inactivation (h_x) of I_Na in ventricular myocytes of crucian carp, rainbow trout and burbot heart. (A) Voltage protocol for steady-state inactivation and representative recordings of I_Na from c.a. fish at +4°C. Steady-state activation curves were constructed from the I–V curves of Fig. 1 as explained in Materials and methods. (B) Voltage-dependence of steady-state activation and inactivation for w.a. (closed symbols) and c.a. (open symbols) fish (means ± S.E.M.; N=7–21).