Up-regulation of the non-neurogenic cholinergic system in the aorta of spontaneously hypertensive rats

Abstract

Despite the intense interest in the effect of acetylcholine in the vascular system, no evidence has been provided suggesting that endothelial cells are directly innervated by cholinergic neurons. The present study was designed to test whether or not the rat aorta contain the biochemical apparatus needed to synthesize, transport, store and degrade acetylcholine, and if so, whether or not differences in the expression of these components exist between preparations from normotensive Wistar Kyoto rats (WKY) and spontaneously hypertensive rats (SHR). Gene expressions were quantified by real-time PCR. The mRNA expression for the neuronal choline acetyltransferase (which synthesizes acetylcholine from the substrates acetyl CoA and choline), vesicular acetylcholine transporter (which specializes in the trafficking of acetylcholine) and acetylcholine esterase (which breakdowns acetylcholine) were expressed in the aorta of both WKY and SHR. The expression of these enzymes was significantly higher in the latter. These data suggest that acetylcholine synthesis is not limited to the cholinergic nerves, but that the cholinergic transmitter is released directly from the aorta in an autocrine fashion to modulate local blood flow. The enhanced vascular synthesis of acetylcholine in the hypertensive rat may reflect a compensatory response to correct for endothelial dysfunction. This work is funded by the RGC – HKU.