Role of dihydropyridine-sensitive calcium channels in the regulation of norepinephrine release in hypertension

In the present study, in order to elucidate the role of dihydropyridine (DHP)-sensitive calcium (Ca) channels in the regulation of neurotransmitter release in hypertension, we examined the effects of the DHP-sensitive Ca channel blocker nicardipine on norepinephrine (NE) release in blood vessels of spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto (WKY) rats. The stimulation-evoked pressor responses and NE release were significantly greater in the mesenteric arteries of SHR than in the mesenteric arteries of WKY rats. Nicardipine significantly inhibited the stimulation-evoked NE release as well as vasoconstrictor responses in the mesenteric arteries to a greater extent in SHR than in WKY rats. These results demonstrated that nicardipine markedly reduced the stimulation-evoked NE release in blood vessels of SHR, which might suggest that the DHP-sensitive Ca channels could be involved, at least in part, in the regulation of NE release in hypertension.