Abstract
Objective: While higher frequency oscillations (0.021–0.6 Hz) in cutaneous blood flow measured by laser Doppler flowmetry (LDF) relate to oscillations in blood pressure and sympathetic nerve activity, very low-frequency oscillations (VLF, 0.0095–0.021 Hz) do not. The authors investigated whether VLF LDF power is nitric oxide (NO) specific.
Methods: LDF combined with intradermal microdialysis was used in the calves of 22 healthy volunteers aged 19–27 years. LDF power spectral analysis was performed by windowed fast Fourier transform. The authors tested whether the NO synthesis inhibitor nitro-l-arginine (NLA) produced selective decreases in VLF power before and after stimulation with acetylcholine.
Results: NLA alone did not alter total power but selectively reduced VLF power by approximately 50%. LDF and spectral power increased markedly across all spectra with acetylcholine. This increase was blunted by NLA, which selectively reduced VLF power by approximately 50%. Conclusions: The data suggest that VLF oscillations in the laser Doppler signal are NO dependent, increase with cholinergic stimulation, and have potential as a noninvasive marker for NO-dependent microvascular reactivity.
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We thank Leonard Newman and the Division of Pediatric Cardiology, especially, Michael H. Gewitz, for their unflagging support. We also thank Thomas H. Hintze, David Robertson, and Phillip Low for their constant inspiration and stimulation. This work was supported by 1RO1HL074873 from the National Heart Lung and Blood Institute and by 1R21DK071647 from the National Institute of Diabetes and Digestive and Kidney Diseases of the National Institutes of Health.