M-currents are absent in embryonic <i>KCNQ2</i>−/− mice and reduced in <i>KCNQ2</i>+/− mice.

<p>A, representative currents recorded from +/+, +/− and −/− sympathetic neurons. Currents were recorded using a standard deactivation protocol to isolate I_K(M) from other voltage-activated currents. The cell was depolarized to −20 mV to pre-activate I_K(M), then hyperpolarized for 1 s to deactivate the current. B, mean current density of the deactivation tail currents on stepping from −20 mV to −50 mV recorded from +/+, +/− and −/− neurons (with numbers of neurons in brackets). Note the different scales in A and B (A: pA total current; B: pA.pF⁻¹).