Age‐Associated Differences in Central Artery Responsiveness to Sympathoexcitation: Influence of Blood Pressure

Abstract

Aging is associated with increased central artery stiffness, a potential consequence of greater tonic sympathetic nerve activity. However, less is known regarding age‐associated changes in central artery responsiveness to acute sympathoexcitation. Therefore, we tested the hypothesis that older adults would demonstrate greater increases in central artery stiffness (carotid‐femoral pulse wave velocity, cfPWV) and wave reflection (augmentation index, AIx) during the cold pressor test (CPT) compared to young adults. To control for the potential confound of blood pressure on our measurements we also employed lower‐body negative pressure (LBNP), a sympathoexcitatory stimuli with minimal influence on blood pressure. We hypothesized that older adults would have less reduction in AIx during LBNP compared to the young adults. Fourteen young (25±4yrs) and 15 older (68±4yrs) subjects completed three minutes of LBNP and CPT on a single study visit, separated by a 15‐minute washout period, in random order. Duplicate measures of cfPWV and AIx were taken at baseline and during the final minute of each perturbation. Baseline heart rate and mean arterial pressure (MAP) were not different between groups (p≥0.05 for both); however, young subjects had lower baseline cfPWV and AIx compared to older subjects (p<0.05 for both). In response to the CPT, heart rate, MAP, cfPWV, and AIx increased in both young and older groups (main effect of time p<0.01 for all); however, the change (Δ) in MAP (18±7 vs. 9±5mmHg), cfPWV (1.3±0.7 vs. 0.6±0.9m·sec−1), and AIx (17±9 vs. 7±4%) were greater in young compared to older subjects, respectively (p<0.05 for all). In response to LBNP, the changes (Δ) in MAP (−1±3 vs. −3±5mmHg), and cfPWV (0.5±0.3 vs. 0.5±0.7m·sec−1) were similar between age groups (main effect of time p<0.05 for all) although young subjects showed a greater reduction in AIx compared to their older counterparts (−8±7 vs. −2±6%, p<0.01). Interestingly, when MAP was used as a covariate, the group‐by‐time interaction for cfPWV and AIx during the CPT as well as AIx during LBNP were no longer significant (p=0.48, 0.11, and 0.39, respectively). Given that the age‐associated differences in cfPWV responsiveness to the CPT was mitigated with MAP as a covariate, and the increase in cfPWV was not different between groups in response to LBNP (no change in MAP), our data suggest age‐associated differences in central artery responsiveness to sympathoexcitation are greatly influenced by changes in MAP.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.