Activation of phosphatidylcholine-selective phospholipase C by I-1-imidazoline receptors in PC12 cells and rostral ventrolateral medulla

The I-1-imidazoline receptor is expressed in the rostral ventrolateral medulla (RVLM) where it mediates vasodepression, and in PC12 pheochromocytoma cells where it elicits generation of diacylglycerol independent of phosphatidylinositol turnover or activation of phospholipase D. We hypothesized that the I-1-imidazoline receptor couples to a phosphatidylcholine-selective phospholipase C (PC-PLC). The I-1-agonist moxonidine elicited diacyglyceride accumulation and release of [H-3]phosphocholine from PC12 cells prelabeled with [H-3]choline. The PC-PLC inhibitor D609 abolished both responses, Microinjection of D609 into the RVLM of hypertensive rats blocked the vasodepressor response to intravenous moxonidine. These data implicate PC-PLC in cellular and organismic responses to I-1-receptor stimulation.