Fig. 1

Linopirdine-sensitive non-inactivating K⁺ currents and KCNQ2 expression at NRs of lumbar spinal ventral nerves. A Bright image (left) and fluorescent image (right) show the same region of an L5 lumbar spinal ventral nerve viewed under a 40 × objective. Arrow indicates a node of Ranvier (NR) and a patch-clamp recording electrode tip. Alexa Fluor 555 (85 μM) was included in the recording electrode internal solution for axon labelling. B Sample traces show currents recorded at a NR following voltage steps in the absence (left, control) and presence of 100 µM linopirdine (right). C I–V curves at the beginning part (left panel) and the end part (right panel) of non-inactivating outward currents in the control (n = 10, open symbols) and the presence of linopirdine (n = 10, red symbols). D Area under the I–V curve (AUC) of the beginning (left panel) and the end part (right panel) of non-inactivating outward currents in the control (n = 10, open bar) and the presence of linopirdine (n = 10, red bar). E Left panel, sample traces show linopirdine-sensitive outward currents obtained by subtraction of total outward currents in the presence of linopirdine from total currents in the control. Right panel, I–V curves of the linopirdine-sensitive outward currents at the end part (n = 10, solid circles). F, G KCNQ2-immunoreactivity (KCNQ2-ir, F) and caspr-ir (G) on lumbar spinal ventral nerves. H Overlay image of (F) and (G) shows that KCNQ2-ir is located in the space between caspr-ir, the region of NRs. Data represent mean ± SEM, **p < 0.01, ***p < 0.001, paired Student’s t-Test