Effects of caffeine on baroreflex activity in humans

Abstract

The effects of caffeine or placebo on blood pressure, heart rate, and baroreflex activation (elicited by phenylephrine) were studied on young normotensive volunteers after a 7-day caffeine-free period. Subjects received oral doses of either 250 mg caffeine (n = 6) or placebo (n = 4), and hemodynamic changes were studied at 0, 30, 60, 120, and 180 minutes after drug administration. Thirty minutes after the caffeine dose, blood pressure had risen from 127 +/- 8/57 +/- 4 mm Hg to 136 +/- 3/68 +/- 5 mm Hg, heart rate was unchanged, and the baroreflex slope had decreased from 31 +/- 7 msec/mm Hg to 11.6 +/- 2 msec/mm Hg. Baroreflex sensitivity remained inhibited for the rest of the single-dose experimental period. In contrast, no significant changes were observed after either long-term caffeine ingestion in the same group or in the placebo group during the single- or multiple-dose study. These findings indicate that single but not multiple caffeine administration inhibits baroreflex activation in normotensive volunteers and this could contribute to the acute hemodynamic effects of caffeine.

Coffee, caffeine and blood pressure: a critical review

“…The re¯ex activation of baroreceptors is supported by a recent study using power spectral analysis, in which an increase in parasympathetic nerve activity was observed in normotensive subjects (Hibino et al, 1997). On the other hand, a single dose of caffeine reduced baroreceptor sensitivity simultaneously with an increase in blood pressure in normotensive subjects (Mosqueda-Garcia et al, 1990). The effects were not seen after multiple doses of caffeine over one week, possibly due to the development of tolerance to the hemodynamic effects of caffeine.…”

Uncoupling of the Baroreflex by N N -Cholinergic Blockade in Dissecting the Components of Cardiovascular Regulation

“…Many disorders that may have changes in adrenoreceptor sensitivity or nitric oxide metabolism have also been shown to have changes in baroreflex function. 9,12,32 Even commonly used medications (eg, digoxin) 33 and dietary substances (eg, caffeine) 34 may affect baroreflex function. Furthermore, in normal subjects, the interindividual variability of baroreflex sensitivity appears to be relatively large.…”

Sympathetic and baroreceptor reflex function in neurally mediated syncope evoked by tilt.

“…Quantification of baroreflex responses to pharmacological manipulations of blood pressure used least squares regression analysis, as reported previously (25). Intervals between each R wave of the EKG (R-R intervals) and sympathetic nerve activity were averaged during the maximal change in BP.…”