Fig. 1

KCNQ channels in nociceptive cold-sensing trigeminal neurons. a Image shows KCNQ2 immunoreactivity (KCNQ2-ir) in a trigeminal ganglion section. b Sample traces of M-currents in the absence (black) and presence (red) of 20 µM linopirdine. The voltage step used to reveal M-currents was shown under the recording traces. The box indicates the M-currents, measured by the tail currents after the voltage step. c I–V curve of tail currents in the absence (black) and presence (red) of 20 µM linopirdine. d Ca²⁺-imaging shows an example of pre-identification of cold-sensing TG neurons with menthol (100 µM). e An example of a pre-identified cold-sensing TG neuron that responded to a cooling temperature ramp by firing action potentials. The cell was under the whole-cell current-clamp recording mode. The cooling ramp from 24 to 8°C is indicated under the recording trace. f Traces on the top panel show a nociceptive cold-sensing neuron that responds to 10 current-steps at the increment of 30 pA and the cell fires a slow action potential (Rheobase = 300 pA) with broad width and a hump in the repolarization phase. A total of 15 cold-sensing TG neurons belong to this category. Traces on the bottom panel show a non-nociceptive cold-sensing neuron that responds to 10 current-steps at the increment of 30 pA and the cell fires a fast action potential (Rheobase = 30 pA) without any hump in the repolarization phase. A total of 21 cold-sensing TG neurons belong to this category. g Traces show a nociceptive cold-sensing neuron that responds to voltage steps from −80 to −20 mV at 10 mV increment. The cell was held at −60 mV. h Summary result of M-currents recorded from nociceptive cold-sensing neurons in the absence (control) and presence of 20 µM linopirdine. The M-currents were measured by the deactivating tail currents following the voltage step of −20 mV. Data represent Mean ± SEM, **P < 0.01.