Figure 5: KCNQ-specific blocker XE991 abolishes ghrelin’s effect on DRG neurons.

(a) Ghrelin increased evoked firing of DRG neurons. The evoked action potentials were shown before (control), during (ghrelin) and after (washout) application of 300 nM ghrelin in the bath (n=7). One or two spikes were produced by a 200-pA depolarizing current pulse in the control, whereas multiple spikes were produced in response to the same current injection in the presence of 300 nM ghrelin. (b) Recording of a cultured DRG neuron under Differential Interference Contrast microscope. Scale bar, 20 μm. (c) XE991 (30 μM, n=5) increased the evoked neuronal firing (left and middle panel). Ghrelin (300 nM, n=5) failed to further increase the evoked neuronal firing in the presence of 30 μM XE991 (right panel). (d) KCNQ currents were recorded before (control), during (ghrelin) and after (washout) application of 300 nM ghrelin using the standard deactivation protocol from −20 to −50 mV. Ghrelin significantly inhibited the KCNQ current (n=9), and the response could be washout (n=5). (e) Statistical analysis of KCNQ currents quantified from all DRG neurons held at −20 to −50 mV in the presence or absence of ghrelin (n=5). The KCNQ current of all DRG neurons were significantly inhibited by 300 nM ghrelin (n=9, **P<0.01, Ghrelin versus Control; t=4.094, Paired t-test). (f) KCNQ current was almost abolished by prolonged application of 30 μM XE991, further application of ghrelin (300 nM) had no effect on residual current. (g) Statistical analysis of f (n=5, **P<0.01, XE991 versus Control; **P<0.01, (XE991+Ghrelin) versus Control; F=19.058, analysis of variance followed by S-N-K test).