Figure 10.
Figure 10. Carbamazepine action on the mutant channels containing Y1618K and glutamate substitutions for the pore loop residues in domain 4. (A) The two superimposed traces show the representative currents elicited from a holding potential of −120 mV to a test depolarization at 0 mV in the absence (black lines) and presence (red lines) of 300 μM carbamazepine. The dotted line indicates zero current level. (B) The macroscopic current decays in A are quantified by the methods in Fig. 1 D to give the relative decay rates for different mutant channels (n = 3–4). (C) The relative decay rates of the macroscopic currents (in 300 μM carbamazepine vs. in control) are examined at different test voltages and in different mutant channels (n = 3–4 for each different channel). Note the apparent lack of voltage dependence of the data from the Y1618K/L1719E double-mutant channel. (D) The decay time constants (in ms) of the macroscopic currents in control (i.e., without any drug) are plotted against different test voltages in different mutant channels (n = 4 for each different channel). The mutant channels in the figure all have significantly faster saturating inactivation kinetics than the wild-type channel. The decay time constants examined at +10 mV for the mutant channels are all ranged between 1.4 ± 0.26 and 2.4 ± 0.41 ms, and that for the wild-type channel (n = 9) is 4.1 ± 0.83 ms (P < 0.001 between any one mutant channel and the wild-type channel compared by Student’s t test). (E) Carbamazepine alters activation of the Y1618K plus L1719E double-mutant channel. The activation curves of the mutant channel were done by the protocols described in Materials and methods. The lines are fits of the data from the same oocyte with a Boltzmann function with V1/2 values (in mV) of −26.9 and −16.8, and k values of 5.1 and 6.1 in the absence (black circles) and presence (white circles) of 300 μM carbamazepine. The averaged shift of the V1/2 of the activation curve by 300 μM carbamazepine is 7.2 ± 2.6 mV (n = 3). The inset contains representative currents elicited by a step depolarization to −20 mV from a holding potential of −120 mV. The dotted vertical line marks the time point when the peak macroscopic current in control (black line) is reached. It is evident that 300 μM carbamazepine (red line) slows the macroscopic activation (rightward shifts the peak of macroscopic current) of the Y1618K plus L1719E mutant channel.

Carbamazepine action on the mutant channels containing Y1618K and glutamate substitutions for the pore loop residues in domain 4. (A) The two superimposed traces show the representative currents elicited from a holding potential of −120 mV to a test depolarization at 0 mV in the absence (black lines) and presence (red lines) of 300 μM carbamazepine. The dotted line indicates zero current level. (B) The macroscopic current decays in A are quantified by the methods in Fig. 1 D to give the relative decay rates for different mutant channels (n = 3–4). (C) The relative decay rates of the macroscopic currents (in 300 μM carbamazepine vs. in control) are examined at different test voltages and in different mutant channels (n = 3–4 for each different channel). Note the apparent lack of voltage dependence of the data from the Y1618K/L1719E double-mutant channel. (D) The decay time constants (in ms) of the macroscopic currents in control (i.e., without any drug) are plotted against different test voltages in different mutant channels (n = 4 for each different channel). The mutant channels in the figure all have significantly faster saturating inactivation kinetics than the wild-type channel. The decay time constants examined at +10 mV for the mutant channels are all ranged between 1.4 ± 0.26 and 2.4 ± 0.41 ms, and that for the wild-type channel (n = 9) is 4.1 ± 0.83 ms (P < 0.001 between any one mutant channel and the wild-type channel compared by Student’s t test). (E) Carbamazepine alters activation of the Y1618K plus L1719E double-mutant channel. The activation curves of the mutant channel were done by the protocols described in Materials and methods. The lines are fits of the data from the same oocyte with a Boltzmann function with V1/2 values (in mV) of −26.9 and −16.8, and k values of 5.1 and 6.1 in the absence (black circles) and presence (white circles) of 300 μM carbamazepine. The averaged shift of the V1/2 of the activation curve by 300 μM carbamazepine is 7.2 ± 2.6 mV (n = 3). The inset contains representative currents elicited by a step depolarization to −20 mV from a holding potential of −120 mV. The dotted vertical line marks the time point when the peak macroscopic current in control (black line) is reached. It is evident that 300 μM carbamazepine (red line) slows the macroscopic activation (rightward shifts the peak of macroscopic current) of the Y1618K plus L1719E mutant channel.

This Feature Is Available To Subscribers Only

or Create an Account

Close Modal
Close Modal