title: 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.
authors.affiliation: Department of Pharmacology, Vanderbilt University, Nashville, Tenn.
authors.forename: R
authors.initials: R
authors.lastname: Mosqueda-Garcia
authors.forename: C J
authors.initials: CJ
authors.lastname: Tseng
authors.forename: I
authors.initials: I
authors.lastname: Biaggioni
authors.forename: R M
authors.initials: RM
authors.lastname: Robertson
authors.forename: D
authors.initials: D
authors.lastname: Robertson
mesh_terms: D000284:Administration, Oral; D000328:Adult; D001794:Blood Pressure / Q000187:drug effects; D002110:Caffeine / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D008297:Male; D011311:Pressoreceptors / Q000187:drug effects*; D012018:Reflex / Q000187:drug effects*
chemical_list: D002110:Caffeine