Age-related changes in the control mechanisms for vasomotion in the microcirculation.

Ageing causes deterioration in function and structure of the skin microcirculation which has been reported to reflect similar deterioration in the microcirculation of other organs. The deterioration in function has been shown to reduce the total microvascular blood flow. The objective of our study was to determine the extent to which the three main control mechanisms of cutaneous microcirculation i.e., myogenic, neurogenic, and metabolic (endothelium dependent and non-endothelium dependent) are affected by ageing. We used young (approximately 2 weeks old, n=10) and older (approximately 12 weeks old, n=10) Sprague-Dawley rats. The animals were sedated, their body temperature maintained at 35 - 37 C with a heating blanket and Laser-Doppler Flowmetry recorded from the palmar surface of the forepaw. Perfusion analysis was used to estimate the microvascular blood flow within a selected region of the palm, whilst the spectral composition of flowmotion was analyzed with Continuous Wavelet Transform using the Morlet mother wavelet. We used the following published frequency bands for rats for the spectral analysis of the microcirculation: myogenic (0.20 - 0.70 Hz), neurogenic (0.08 - 0.20 Hz), and metabolic control (0.01 - 0.08 Hz). Statistical significance was examined with one-tailed, two-sample t-Test. The weights (in grams) of the young and older rats were 114±6 and 542±11 (mean±SEM). The skin perfusion for the young and older rats were 377±31 and 189±18 (perfusion units) respectively; the difference was significant with p<0.01. The mean amplitudes of the wavelet components for myogenic, neurogenic, and metabolic microvascular control for the young rats were 56.8, 71.6 and, 105.4 respectively, whilst those for the older rats were 30.4, 48.2, and 63.3; the decreases in the values for the older rats were significant (p<0.05). The study demonstrates that aging causes significant impairment of all the three major control mechanisms that influence cutaneous microcirculation. The results provide an approach to investigate interventions that may affect specific control mechanisms of the microcirculation.