The effect of aging on vasomotion responses to varying rates of local heating.

Abstract

We compared the cutaneous microvascular vasomotion responses of 8 young (23 ± 1 yr) and 8 older (68 ± 2 yr) adults in the forearm and leg using laser‐Doppler fluxmetry (LDF) and wavelet analysis to investigate endothelial, neurogenic, and myogenic activity. We measured cutaneous microvascular responses at uncontrolled basal temperature (27 ± 2.2 °C), controlled basal temperature (33 °C), and initial vasodilation (onset of heating), and sustained vasodilation, at 42 and 44 °C, in response to both a slow (0.1 °C · 10 s‐1) and a fast (0.5 °C · 10 s‐1) local heating protocol. At baseline (no heating), there were no differences between the groups (all P > 0.05). At a controlled local temperature of 33 °C (thermoneutral), neurogenic activity was higher in the leg of the young compared to the older group (P = 0.04). Following the initiation of the heating protocols, the young participants responded with higher neurogenic activity in the forearm compared to the older group during fast local heating (P = 0.03), but not in response to slow local heating (P > 0.05). In the leg, the young group had higher endothelial nitric oxideindependent activity compared to the older group (P = 0.01) for both heating protocols. The young group also had an increase in endothelial nitric oxide‐dependent activity during the slow protocol (P < 0.001), while the older cohort experienced increases in neurogenic (P = 0.02) and myogenic (P = 0.04) activity. Following 35 min at 42 °C, neurogenic activity was significantly increased in the leg of the older group compared to the young group during the slow heating protocol (P = 0.02). Furthermore, after increasing local temperature from 42 to 44 °C, the older adults had higher endothelial nitric oxide‐independent activity (P = 0.04) in the forearm of the fast protocol while the young subjects had higher neurogenic activity (P = 0.04). Neurogenic activity in the leg of the older group was increased (P = 0.02) during the fast protocol at 44 °C. These results suggest that regional differences in the response to local heating persist with age and that the primary mechanisms responsible for vasodilation caused by local heating are diminished with age; however, overall vasodilation is offset by the other mechanisms. Moreover, our results suggest that as we age the reliance on endothelial activity shifts from endothelial nitric oxide‐dependent to endothelial nitric oxide‐independent mechanisms. These data suggest that the cutaneous bioavailability of nitric oxide is diminished with age.Support or Funding InformationBall State University SPA Fellows StipendThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.