Effects of Volatile Anesthetics on Acetylcholine-induced Relaxation in the Rabbit Mesenteric Resistance Artery

Abstract

The results confirm that ACh has a hyperpolarizing action in rabbit small mesenteric resistance arteries that is independent of EDRF inhibitors but blocked by the K+ channel blocker TEA. The ACh relaxation in these resistance arteries thus appears to consist of distinct EDRF-mediated and hyperpolarization-mediated components. Isoflurane, enflurane, and sevoflurane inhibited both components of the ACh-induced relaxation in these small arteries, indicating a more global depression of endothelial function or ACh signaling in endothelial cells, rather than a specific effect on the EDRF pathway. All these anesthetics exerted vasodilating action in the presence of NE, the primary neurotransmitter of the sympathetic nervous system, which plays a major role in maintaining vasomotor tone in vivo. This strongly indicates that the vasodilating action of these anesthetics probably dominates over their inhibitory action on the EDRF pathway and, presumably, contributes to their known hypotensive effects in vivo. Finally, the vasodilating action of these anesthetics is, at least in part, independent from endothelium.