The antidepressant imipramine inhibits M current by activating a phosphatidylinositol 4,5-bisphosphate (PIP 2)-dependent pathway in rat sympathetic neurones

Abstract

Little is known about the intracellular actions of imipramine (IMI) in the regulation of ion channels. We tested the action of IMI on the intracellular cascade that regulates M current (I M) in superior cervical ganglion neurones (SCGs). Dialysis of the cells with GDPβS, a G protein signaling blocker, did not disrupt the inhibition of I M. When we incubated the cells with the phospholipase C (PLC) inhibitor U73122, it prevented the I M inhibition by IMI. Also, when we dialyzed the cells with an intracellular Ca 2+ chelator, it did not disrupt I M inhibition by IMI, as occurs in the M 1 cascade. When we incubated the cells with the generic kinase inhibitor wortmannin, it prevented the recovery of I M from the inhibition by IMI. Also, when we applied phosphatidylinositol 4,5-bisphosphate (PIP 2) intracellularly, it diminished the inhibition of I M by IMI. Our findings suggest that PLC is the target for IMI, that recovery of I M needs lipid phosphorylation for PIP 2 resynthesis, and that IMI inhibits I M by activating a PLC-dependent pathway, likely by decreasing the concentration of PIP 2. © 2005 Nature Publishing Group. All rights reserved.