Effects of changes in central blood volume on carotid-vasomotor baroreflex sensitivity at rest and during exercise.
The purpose of this investigation was to examine whether the effect of changes in central blood volume on carotid-vasomotor baroreflex sensitivity at rest was the same during exercise. Eight men (means +/- SE: age 26 +/- 1 yr; height 180 +/- 3 cm; weight 86 +/- 6 kg) participated in the present study. Sixteen Torr of lower body negative pressure (LBNP) were applied to decrease central venous pressure (CVP) at rest and during steady-state leg cycling at 50% peak O2 uptake (104 +/- 20 W). Subsequently, infusions of 25% human serum albumin solution were administered to increase CVP at rest and during exercise. During all protocols, heart rate, arterial blood pressure, and CVP were recorded continuously. At each stage of LBNP or albumin infusion, the maximal gain (G(max)) of the carotid-vasomotor baroreflex function curve was measured using the neck pressure and neck suction technique. LBNP reduced CVP and increased the G(max) of the carotid-vasomotor baroreflex function curve at rest (+63 +/- 25%, P = 0.006) and during exercise (+69 +/- 19%, P = 0.002). In contrast to the LBNP, increases in CVP resulted in the G(max) of the carotid-vasomotor baroreflex function curve being decreased at rest -8 +/- 4% and during exercise -18 +/- 5% (P > 0.05). These findings indicate that the relationship between CVP and carotid-vasomotor baroreflex sensitivity was nonlinear at rest and during exercise and suggests a saturation load of the cardiopulmonary baroreceptors at which carotid-vasomotor baroreflex sensitivity remains unchanged.
Ogoh
Shigehiko
S
Department of Integrative Physiology, University of North Texas Health Science Center, 3500 Camp Bowie Blvd., Fort Worth, Texas 76107, USA. sogoh@hsc.unt.edu
Brothers
R Matthew
RM
Barnes
Quinton
Q
Eubank
Wendy L
WL
Hawkins
Megan N
MN
Purkayastha
Sushmita
S
O-Yurvati
Albert
A
Raven
Peter B
PB
D000328:Adult; D017704:Baroreflex / Q000502:physiology*; D001794:Blood Pressure / Q000502:physiology; D001810:Blood Volume / Q000187:drug effects / Q000502:physiology*; D002339:Carotid Arteries / Q000294:innervation / Q000502:physiology*; D015444:Exercise / Q000502:physiology*; D005169:Factor VIII / Q000502:physiology; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D020896:Hypovolemia / Q000503:physiopathology; D008150:Lower Body Negative Pressure; D008297:Male; D011311:Pressoreceptors / Q000502:physiology; D012146:Rest / Q000502:physiology*; D012709:Serum Albumin / Q000494:pharmacology; D014666:Vasomotor System / Q000502:physiology*
D012709:Serum Albumin; D005169:Factor VIII