Involvement of TRPV4 in changes in rapidly inactivating potassium channels in the early stage of pilocarpine‐induced status epilepticus in mice

Abstract

The rapidly inactivating potassium current (I A ) is important in controlling neuronal action potentials. Altered I A function and K + channel expression have been found in epilepsy, and activation of the transient receptor potential vanilloid 4 (TRPV4) channel is involved in epilepsy pathogenesis. This study examined whether TRPV4 affects Kv4.2 and K + channel interacting protein (KCHIP) expression and I A changes following pilocarpine-induced status epilepticus (PISE) in mice. Herein, hippocampal protein levels of Kv4.2 and KCHIP2 increased 3 h-3 d and decreased 7-30 d; that of KCHIP1 increased 3-24 h and decreased 3-30 d post-PISE. The TRPV4 antagonist HC-067047 attenuated the increased protein levels of Kv4.2 and KCHIP2 but not that of KCHIP1 post-PISE. The TRPV4 agonist GSK1016790A increased hippocampal protein levels of Kv4.2 and KCHIP2 but had no effect on KCHIP1 expression. HC-067047 attenuated the increased I A in hippocampal pyramidal neurons 24 h and 3 d post-PISE. GSK1016790A increased I A in hippocampal pyramidal neurons, shifting the voltage-dependent inactivation curve toward depolarization. The GSK1016790A-induced increase of I A was blocked by protein kinase A and calcium/ calmodulin-dependent kinase II antagonists but was unaffected by protein kinase C antagonists. We conclude that TRPV4 activation may be responsible for the increases of Kv4.2 and KCHIP2 expression in hippocampi and I A in hippocampal pyramidal neurons in PISE mice, which are likely compensatory measures for hyperexcitability at the early stage of epilepsy.hippocampus, K + channel interacting protein, pilocarpine-induced status epilepticus rapidly inactivating potassium channel, transient receptor potential vanilloid 4