title: The k-complex vasoconstrictor response: evidence for central vasomotor downregulation in borderline hypertension.
abstract: Central sympathetic outflow and the baroreflex were measured as an integrated cardiopressor response to a noise stimulus during normal sleep, in 13 normotensives and 14 borderline hypertensives. The pressor response latency was prolonged in the borderline hypertensives, and the stimulus-induced increase in systolic and diastolic intra-arterial pressure was greater in the borderline hypertensives (23.0 +/- 7.3-16.2 +/- 5.6 mmHg) compared with the normotensives (16.7 +/- 5.9-13.6 +/- 4.6 mmHg; P less than 0.001), but the heart rate was not increased. Despite the increased pressor response, the baroreflex-mediated fall in the heart rate following the pressor response was reduced in the borderline hypertensives, indicating secondary adaptation to hypertension and a resetting, or downregulation, of central vasomotor control mechanisms in the borderline hypertensives relative to normotensives.
authors.affiliation: Department of Medicine, Wellington School of Medicine, New Zealand.
authors.forename: S
authors.initials: S
authors.lastname: Heald
authors.forename: R W
authors.initials: RW
authors.lastname: Siebers
authors.forename: T J
authors.initials: TJ
authors.lastname: Maling
mesh_terms: D000161:Acoustic Stimulation; D001794:Blood Pressure / Q000502:physiology; D015536:Down-Regulation / Q000502:physiology*; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D006973:Hypertension / Q000503:physiopathology*; D011930:Reaction Time / Q000502:physiology; D014661:Vasoconstriction / Q000502:physiology*; D014666:Vasomotor System / Q000503:physiopathology*