Arterial baroreceptor reflex and calcium antagonists.

The tachycardia elicited by decreases in aortic pressure produced by various calcium antagonists, regardless of their chemical structures, is not always simply related to the reduction in pressure. Several experimental and clinical experiments have clearly demonstrated that some of these compounds interfer with the baroreceptor reflex control of heart rate. The voltage-dependent calcium channel blockade induced by these antagonists is probably not involved in the baroreceptor mechanotransduction, but central modulation of the baroreceptor reflex is probably an important site for action of these drugs at therapeutic levels. During chronic treatment of hypertension with calcium antagonists, a resetting of the reflex occurred with parallel shift of the set-point and of the baroreceptor reflex-response curve towards lower pressures, thus explaining the lack of change in heart rate despite a permanent reduction in blood pressure under these conditions. However, these effects of calcium antagonists on the baroreceptor reflex do not provide evidence that such interactions could play a role in their antihypertensive action during chronic therapy.