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 pheochro mocytoma cells where it elicits generation of diacylglycerol independe nt of phosphatidylinositol turnover or activation of phospholipase D. We hypothesized that the I-1-imidazoline receptor couples to a phospha tidylcholine-selective phospholipase C (PC-PLC). The I-1-agonist moxon idine elicited diacyglyceride accumulation and release of [H-3]phospho choline from PC12 cells prelabeled with [H-3]choline. The PC-PLC inhib itor D609 abolished both responses, Microinjection of D609 into the RV LM of hypertensive rats blocked the vasodepressor response to intraven ous moxonidine. These data implicate PC-PLC in cellular and organismic responses to I-1-receptor stimulation.