Figure 4. Carbamazepine acutely inhibits channel response to MgADP and MgGTP in isolated membrane patches. (Ai) Representative inside-out patch-clamp recording from COSm6 cells expressing WT channels without overnight carbamazepine treatment. Channels were exposed sequentially to various bath solutions as indicated by the bars above the recording. (Aii) Average currents at the various time points marked in the current trace shown in (Ai) are expressed as percent of those observed immediately after patch excision into K-INT solution. Asterisks indicate statistical significance (P < 0.05, n = 3) between the 2 time points using 2-tailed, paired Student t test. (Bi) Representative recording showing the stimulatory effect of 1 mM GTP and inhibition of this effect by carbamazepine. Note the patch was excised into K-INT solution and allowed to run down to a steady level before being exposed to 1mM GTP (free [Mg²⁺]~1mM). (Bii) Quantification of channel activity in 1 mM GTP or 1 mM GTP plus 10 µM carbamazepine as % of currents observed in K-INT. * P < 0.05 by 2-tailed, unpaired Student t test, n = 6 and 3 for 1 mM GTP and 1 mM GTP plus 10 µM carbamazepine, respectively.