title: Baroreflex buffering and susceptibility to vasoactive drugs.
abstract: BACKGROUND
  The overall effect of vasoactive drugs on blood pressure is determined by a combination of the direct effect on vascular tone and an indirect baroreflex-mediated effect, a baroreflex buffering of blood pressure. Differences in baroreflex function affect the responsiveness to vasoactive medications, particularly baroreflex buffering of blood pressure; however, the magnitude is not known.
  
  
  RESULTS
  We characterized baroreflex function and responses to vasoactive drugs in patients with idiopathic orthostatic intolerance, patients with essential hypertension, patients with monogenic hypertension and brachydactyly, patients with multiple system atrophy, and control subjects. We used phenylephrine sensitivity during ganglionic blockade as a measure of baroreflex buffering. Phenylephrine (25 microg) increased systolic blood pressure 6+/-1.6 mm Hg in control subjects, 6+/-1.1 mm Hg in orthostatic intolerance patients, 18+/-3.9 mm Hg in patients with essential hypertension, 31+/-3.4 mm Hg in patients with monogenic hypertension, and 25+/-3.4 mm Hg in patients with multiple system atrophy. Similar differences in sensitivities between groups were observed with nitroprusside. The sensitivity to vasoactive drugs was highly correlated with baroreflex buffering function and to a lesser degree with baroreflex control of heart rate. In control subjects, sensitivities to nitroprusside and phenylephrine infusions were correlated with baroreflex heart rate control and sympathetic nerve traffic.
  
  
  CONCLUSIONS
  Our findings are consistent with an important effect of baroreflex blood pressure buffering on the sensitivity to vasoactive drugs. They suggest that even moderate changes in baroreflex function may have a substantial effect on the sensitivity to vasoactive medications.
authors.affiliation: Franz-Volhard Clinical Research Center and Helios Klinikum, Medical Faculty of the Charité, Humboldt-University, Berlin, Germany. jordan@fvk-berlin.de
authors.forename: Jens
authors.initials: J
authors.lastname: Jordan
authors.forename: Jens
authors.initials: J
authors.lastname: Tank
authors.forename: John R
authors.initials: JR
authors.lastname: Shannon
authors.forename: Andre
authors.initials: A
authors.lastname: Diedrich
authors.forename: Axel
authors.initials: A
authors.lastname: Lipp
authors.forename: Christoph
authors.initials: C
authors.lastname: Schröder
authors.forename: Guy
authors.initials: G
authors.lastname: Arnold
authors.forename: Arya M
authors.initials: AM
authors.lastname: Sharma
authors.forename: Italo
authors.initials: I
authors.lastname: Biaggioni
authors.forename: David
authors.initials: D
authors.lastname: Robertson
authors.forename: Friedrich C
authors.initials: FC
authors.lastname: Luft
mesh_terms: D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000328:Adult; D017704:Baroreflex / Q000187:drug effects*; D001794:Blood Pressure / Q000187:drug effects; D004032:Diet; D004305:Dose-Response Relationship, Drug; D004562:Electrocardiography; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D006973:Hypertension / Q000175:diagnosis / Q000503:physiopathology*; D007024:Hypotension, Orthostatic / Q000175:diagnosis / Q000503:physiopathology*; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D008875:Middle Aged; D019578:Multiple System Atrophy / Q000175:diagnosis / Q000503:physiopathology*; D009599:Nitroprusside / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D011187:Posture; D013564:Sympathetic Nervous System / Q000187:drug effects / Q000503:physiopathology; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014665:Vasodilator Agents / Q000494:pharmacology; D014666:Vasomotor System / Q000187:drug effects / Q000503:physiopathology
chemical_list: D000318:Adrenergic beta-Agonists; D014662:Vasoconstrictor Agents; D014665:Vasodilator Agents; D009599:Nitroprusside; D010656:Phenylephrine; D007545:Isoproterenol