Effects of ketanserin, verapamil and diltiazem on vascular sympathetic nerve activity in hypertension.

This study was carried out to investigate the hypotensive mechanisms of ketanserin and Ca-antagonists (verapamil and diltiazem) in hypertension. Perfused mesenteric vasculatures were prepared in spontaneously hypertensive rats (SHR, Okamoto and Aoki strain) and age-matched Wistar Kyoto rats (WKY), and the effects of these drugs on vascular responsiveness and norepinephrine release from the sympathetic nerve endings were examined. Pressor responses and endogenous norepinephrine release during periarterial nerve stimulation were significantly increased in SHR compared with age-matched WKY. Ketanserin, verapamil and diltiazem inhibited the stimulation-evoked pressor responses and norepinephrine release dose-dependently, respectively. The suppressive magnitudes of these responses by ketanserin, verapamil and diltiazem were greater in SHR than in WKY. The results demonstrate that ketanserin, verapamil and diltiazem might inhibit norepinephrine release from the vascular adrenergic neurons more strongly in hypertension. This sympatho-depressive effect may contribute, at least partially, to the hypotensive mechanisms of these antihypertensive drugs.