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Abstract : |
To examine the possible age-related blood pressure (BP) deregulation in response to central hypervolemia, we measured spontaneous baroreflex sensitivity (SBRS), carotid arterial compliance (CC), and R-R interval coefficient of variation (RRICV) during basal and thermoneutral resting head-out-of-water immersion (HOWI) in 7 young (YG = 24.0 آ± 0.8 years) and 6 middle-aged/older (OL = 59.3 آ± 1.3 years) healthy men. Compared with basal conditions (YG = 19.6 آ± 4.0 vs OL = 6.1 آ± 1.5 ms/mmHg, P < 0.05), SBRS remained higher in YG than OL during rest HOWI (YG = 23.6 آ± 6.6 vs OL = 9.3 آ± 2.1 ms/mmHg, P < 0.05). The RRICV was significantly different between groups (YG = 6.5 آ± 1.4 vs OL = 2.8 آ± 0.4%, P < 0.05) under HOWI. The OL group had no increase in CC, but a significant increase in systolic BP (basal = 115.3 آ± 4.4 vs water = 129.3 آ± 5.3 mmHg, P < 0.05) under HOWI. In contrast, the YG group had a significant increase in CC (basal = 0.16 آ± 0.01 vs water = 0.17 آ± 0.02 mmآ²/mmHg, P < 0.05) with no changes in systolic BP. SBRS was positively related to CC (r = 0.58, P < 0.05 for basal vs r = 0.62, P < 0.05 for water). Our data suggest that age-related vagal dysfunction and reduced CC may be associated with SBRS differences between YG and OL groups, and with BP elevation during HOWI in healthy older men., |
