Table 1

Comparison of M-current and cloned potassium channels: IC50 for linopirdine and XE991 blockade. The number of cells is indicated in parentheses. IC50 values (mean ± SEM) are expressed in micromolar. In cases where the IC50 values were >100 μM, the exact value is not reported owing to limited solubility of the drug. It has been suggested that eag-related potassium channels might encode the M-current (29), and all theeag-related channels expressed in SCG (26) were tested in addition to representative examples of delayed-rectifier and A-channels.

M-currentKCNQ2 +KCNQ3 KCNQ2 KCNQ1 eag1 erg1 erg3elk1 Kv1.2 Kv4.3
XE991
0.98 ± 0.150.6 ± 0.1 0.71 ± 0.07 0.75 ± 0.05 49 ± 6* >100 >100 >100 >10043 ± 7
(3)(6)(6)(7)(6)(4)(6)(5)(5)(5)
Linopirdine
7.0 ± 1.1 4.0 ± 0.5 4.8 ± 0.68.9 ± 0.9 31 ± 3* 53 ± 4 85 ± 537 ± 4 68 ± 6 86 ± 14
(5)(6)(5)(6)(9)(6)(5)(7)(4)(4)
  • * Blockade of the eag1 channel was incomplete with 82  ±  1% (n = 4) blockade by 1 mM linopirdine and 56  ±  2% (n = 6) blockade by 100 μM XE991.

  • Data adapted from Costa and Brown (23); a similar value of 3.4  ±  0.3 μM was obtained by Lamas et al.(22).

  • The IC50 for block of elk1 channels by linopirdine was highly voltage dependent, and the value shown is for a step to −10 mV. IC50 values ranged from 26  ±  3 μM at −20 mV (n = 7) to 144  ±  10 μM at +30 mV (n = 3).