Mechanosensitivity of voltage-gated K⁺ currents in rat trigeminal ganglion neurons

We investigated the mechanosensitivity of voltage-gated K⁺ channel (VGPC) currents by using whole-cell patch clamp recording in rat trigeminal ganglion (TG) neurons. On the basis of biophysical and pharmacological properties, two types of VGPC currents were isolated. One was transient (I_K,A), the other sustained (I_K,V). Hypotonic stimulation (200 mOsm) markedly increased both I_K,A and I_K,V without affecting their activation and inactivation kinetics. Gadolinium, a well-known blocker of mechanosensitive channels, failed to block the enhancement of I_K,A and I_K,V induced by hypotonic stimulation. During hypotonic stimulation, cytochalasin D, an actin-based cytoskeletal disruptor, further increased I_K,A and I_K,V, whereas phalloidin, an actin-based cytoskeletal stabilizer, reduced I_K,A and I_K,V. Confocal imaging with Texas red-phalloidin showed that actin-based cytoskeleton was disrupted by hypotonic stimulation, which was similar to the effect of cytochalasin D. Our results suggest that both I_K,A and I_K,V are mechanosensitive and that actin-based cytoskeleton is likely to regulate the mechanosensitivity of VGPC currents in TG neurons.