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.