title: Impaired carotid baroreflex control of arterial blood pressure in multiple sclerosis.
abstract: Multiple sclerosis (MS), a progressive neurological disease, can lead to impairments in the autonomic control of cardiovascular function. We tested the hypothesis that individuals with relapsing-remitting MS (n = 10; 7 females, 3 males; 13 ± 4 yr from diagnosis) exhibit impaired carotid baroreflex control of blood pressure and heart rate compared with sex, age, and body weight-matched healthy individuals (CON: n = 10; 7 females, 3 males). At rest, 5-s trials of neck pressure (NP; +40 Torr) and neck suction (NS; -60 Torr) were applied to simulate carotid hypotension and hypertension, respectively, while mean arterial pressure (MAP; finger photoplethysmography), heart rate (HR), cardiac output (CO; Modelflow), and total vascular conductance (TVC) were continuously measured. In response to NP, there was a blunted increase in peak MAP responses (MS: 5 ± 2 mmHg) in individuals with MS compared with healthy controls (CON: 9 ± 3 mmHg; P = 0.005), whereas peak HR responses were not different between groups. At the peak MAP response to NP, individuals with MS demonstrated an attenuated decrease in TVC (MS, -10 ± 4% baseline vs. CON, -15 ± 4% baseline, P = 0.012), whereas changes in CO were similar between groups. Following NS, all cardiovascular responses (i.e., nadir MAP and HR and percent changes in CO and TVC) were not different between MS and CON groups. These data suggest that individuals with MS have impaired carotid baroreflex control of blood pressure via a blunted vascular conductance response resulting in a diminished ability to increase MAP in response to a hypotensive challenge.
authors.affiliation: Applied Physiology and Wellness, Southern Methodist University, Dallas, Texas;
authors.forename: Mu
authors.initials: M
authors.lastname: Huang
authors.affiliation: Applied Physiology and Wellness, Southern Methodist University, Dallas, Texas; Kinesiology, University of Texas at Arlington, Arlington, Texas; and.
authors.forename: Dustin R
authors.initials: DR
authors.lastname: Allen
authors.affiliation: Kinesiology, University of Texas at Arlington, Arlington, Texas; and.
authors.forename: David M
authors.initials: DM
authors.lastname: Keller
authors.affiliation: Kinesiology, University of Texas at Arlington, Arlington, Texas; and.
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Fadel
authors.affiliation: Neurology and Neurotherapeutics, University of Texas Southwestern Medical Center, Dallas, Texas.
authors.forename: Elliot M
authors.initials: EM
authors.lastname: Frohman
authors.affiliation: Applied Physiology and Wellness, Southern Methodist University, Dallas, Texas; Neurology and Neurotherapeutics, University of Texas Southwestern Medical Center, Dallas, Texas sldavis@smu.edu.
authors.forename: Scott L
authors.initials: SL
authors.lastname: Davis
mesh_terms: D000328:Adult; D017704:Baroreflex / Q000502:physiology*; D001794:Blood Pressure / Q000502:physiology*; D002339:Carotid Arteries / Q000503:physiopathology*; D017097:Electric Impedance; D004562:Electrocardiography; D005260:Female; D005385:Fingers / Q000503:physiopathology; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D006973:Hypertension / Q000503:physiopathology; D007022:Hypotension / Q000503:physiopathology; D008297:Male; D020529:Multiple Sclerosis, Relapsing-Remitting / Q000503:physiopathology*; D017156:Photoplethysmography; D010812:Physical Stimulation; D011312:Pressure; D012119:Respiration
keywords: baroreceptors; carotid hypertension; carotid hypotension; heart rate; sympathetic nervous system