title: Cardiopulmonary baroreflex is reset during dynamic exercise.
abstract: The purpose of this study was to examine the hypothesis that the operating point of the cardiopulmonary baroreflex resets to the higher cardiac filling pressure of exercise associated with the increased cardiac filling volumes. Eight men (age 26 +/- 1 yr; height 180 +/- 3 cm; weight 86 +/- 6 kg; means +/- SE) participated in the present study. Lower body negative pressure (LBNP) was applied at 8 and 16 Torr to decrease central venous pressure (CVP) at rest and during steady-state leg cycling at 50% peak oxygen uptake (104 +/- 20 W). Subsequently, two discrete infusions of 25% human serum albumin solution were administered until CVP was increased by 1.8 +/- 0.6 and 2.4 +/- 0.4 mmHg at rest and 2.9 +/- 0.9 and 4.6 +/- 0.9 mmHg during exercise. During all protocols, heart rate, arterial blood pressure, and CVP were recorded continuously. At each stage of LBNP or albumin infusion, forearm blood flow and cardiac output were measured. During exercise, forearm vascular conductance increased from 7.5 +/- 0.5 to 8.7 +/- 0.6 U (P = 0.024) and total systemic vascular conductance from 7.2 +/- 0.2 to 13.5 +/- 0.9 l.min(-1).mmHg(-1) (P < 0.001). However, there was no significant difference in the responses of both forearm vascular conductance and total systemic vascular conductance to LBNP and the infusion of albumin between rest and exercise. These data indicate that the cardiopulmonary baroreflex had been reset during exercise to the new operating point associated with the exercise-induced change in cardiac filling volume.
authors.affiliation: Department of Integrative Physiology, University of North Texas Health Science Center, 3500 Camp Bowie Blvd., Fort Worth, Texas 76107, USA. sogoh@hsc.unt.edu
authors.forename: Shigehiko
authors.initials: S
authors.lastname: Ogoh
authors.forename: R Matthew
authors.initials: RM
authors.lastname: Brothers
authors.forename: Quinton
authors.initials: Q
authors.lastname: Barnes
authors.forename: Wendy L
authors.initials: WL
authors.lastname: Eubank
authors.forename: Megan N
authors.initials: MN
authors.lastname: Hawkins
authors.forename: Sushmita
authors.initials: S
authors.lastname: Purkayastha
authors.forename: Albert
authors.initials: A
authors.lastname: O-Yurvati
authors.forename: Peter B
authors.initials: PB
authors.lastname: Raven
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology; D000328:Adult; D017704:Baroreflex / Q000502:physiology*; D001794:Blood Pressure / Q000502:physiology*; D001810:Blood Volume / Q000502:physiology*; D002496:Central Venous Pressure / Q000502:physiology*; D005080:Exercise Test; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008150:Lower Body Negative Pressure / Q000379:methods; D008297:Male; D010807:Physical Endurance / Q000502:physiology*; D005082:Physical Exertion / Q000502:physiology*