Figure 7.

Effect of MGB on persistent I_Na (I_Na(P)) activated in response to upright isosceles triangular V_ramp, which was utilized to mimic the depolarizing or repolarizing slopes of bursting patterns in electrically excitable cells. (A) Representative current traces activated by isosceles triangular V_ramp for a duration of 8 s, or with a ramp speed of ± 75 mV/s (indicated in the uppermost part). The black color in the upper and lower part of (A) indicates the current trace activated by the ascending limb of the V_ramp, while the red color shows trace activated by the V_ramp’s descending limb. The uppermost part depicts the voltage protocol applied. The purple curved arrow indicates the direction of the current over which time goes during the activation of the triangular ramp pulse. Of note, there is a voltage-dependent hysteresis V_hys (i.e., figure of eight configuration) of I_Na(P) evoked by the isosceles triangular V_ramp with or without the MGB (10 μM) addition. In (B,C), summary bar graphs, respectively, show inhibitory effects of MGB (3 or 10 μM) on the amplitude of I_Na(P) activated by the upsloping (at −10 mV) and downsloping (at −80 mV) limb of the triangular V_ramp (mean ± SEM; n = 7 for each bar). ^* This result is significantly different from controls (p < 0.05).