[Effects of m-nisoldipine on arterial baroreflex sensitivity in anesthetized rats]

Baroreflex sensitivity (BRS) in anesthetized rats was measured as the slope of the regression line of the concomitant maximal change in heart rate (delta R-R) and blood pressure (delta BP) induced by bolus i.v. phenylephrine or sodium nitroprusside, m-nisoldipine (m-Nis) i.v. 5, 10, 20 micrograms.kg-1 depressed the BRS (2.6 +/- 0.2, 2.4 +/- 0.3, 1.6 +/- 0.2, or 1.7 +/- 0.1, 1.6 +/- 0.2, and 1.4 +/- 0.2 ms.kPa-1, respectively) compared with before medication (P < 0.01). m-Nis may act directly on carotid sinus to depress the BRS, but not through cardiac beta or M receptor nor through central nervous system.