Endothelin-1 enhances responses to sympathetic nerve stimulation in endothelium-denuded and endothelium-intact rabbit ear arteries

In the rabbit isolated and endothelium-denuded ear artery, endothelin-1 (1–10 nM) elicited concentration-dependent vasoconstrictor responses. Lower concentrations of endothelin-1 (0.1, 0.3 and 1 nM) with little or no direct vasoconstrictor action significantly enhanced responses to sympathetic nerve stimulation in both endothelium-denuded and endothelium-intact arteries. The vasoconstrictor action of endothelin-1 and its enhancing effect on stimulation-induced responses were significantly decreased by the presence of the dihydropyridine-type calcium channel antagonist nicardipine (10 nM). The enhancing effect of low concentrations of endothelin-1 on responses to sympathetic nerve stimulation may play a role in the regulation of vascular tone.