Unilateral carotid-cardiac baroreflex responses in exercise trained and untrained men

To determine effects of aerobic exercise training on individual contributions of the right and left carotid sinus baroreflex control of the cardiac interval, heart rate [expressed as R-R Interval (RRI)] and mean arterial pressure (MAP) responses were elicited by pulsed trains of neck suction and pressure in exercise trained (ET = 8) and untrained (UT = 8) men. ET subjects had a greater (mean ± SD) maximal oxygen uptake (VO_2max) than UT subjects (ET = 64.5 ± 2.4 ml-kg-min^-l vs UT = 39.8 ± 3.7 ml-kg-min^-l; P < 0.001). A neck collar device was modified for delivery of suction and pressure pulses to only one side of the neck. Carotid-cardiac gains for right, left, and bilateral baroreflexes were determined from the logistic function of RRI responses to changes in estimated carotid sinus pressure (ECSP). There were no significant differences in the maximal gains for bilateral (ET = 6.4 ± 1.8 vs UT = 5.9 ± 1.3 ms•mm Hg^-l ECSP), right sided (ET = 5.3 ± 1.2 vs UT = 4.5 ± 1.2 ms•mm Hg^-l ECSP) or left sided (ET = 3.3 ± 1.8 vs UT = 3.6 ±1.8 ms•mm Hg^-l ECSP) responses between groups and both groups demonstrated an inhibitory summation of reflexes. We suggest that right and left carotid-cardiac responses, as well as the summation of these reflexes, are quantitatively similar in exercise trained and untrained subjects.