Antihypertensive drugs distinctly modulate the rapid resetting of the baroreceptors.

We investigated the distinct ability of various antihypertensive drugs to modulate the extent (%) of rapid (15 minutes) resetting of the baroreceptors of normotensive rats to hypotensive levels. In one protocol, hemorrhage produced a complete resetting to hypotension in rats chronically treated (6 days) with captopril. Also, hemorrhage produced only partial resetting in rats acutely treated (10-15 minutes before baroreceptor recording) with captopril and in control (untreated) rats (73 +/- 7% and 49 +/- 5%, respectively). In another protocol, all vasodilators produced hypotension in normotensive rats. Nifedipine produced complete (93 +/- 4%) resetting to hypotension, whereas prazosin produced near-maximal (83 +/- 3%) resetting. The remaining drugs studied (phenoxybenzamine, trimethaphan, and MgSO4) induced a partial resetting (63 +/- 7%, 63 +/- 9%, and 50 +/- 5%, respectively) that did not differ significantly from the extent observed with hemorrhage in control (untreated) rats. These results demonstrate that different antihypertensive drugs distinctly modulate rapid baroreceptor resetting to hypotensive levels and that nifedipine and long-term treatment with captopril associated with hemorrhage modulate rapid resetting to hypotension in a more efficient manner.