Noninvasive measure of microvascular nitric oxide function in humans using very low-frequency cutaneous laser Doppler flow spectra.
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.
Stewart
Julian M
JM
New York Medical College, Valhalla, New York, USA. stewart@nymc.edu
Taneja
Indu
I
Goligorsky
Michael S
MS
Medow
Marvin S
MS
D000109:Acetylcholine / Q000008:administration & dosage*; D000328:Adult; D001794:Blood Pressure / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000008:administration & dosage*; D005260:Female; D006801:Humans; D017078:Laser-Doppler Flowmetry; D008297:Male; D009569:Nitric Oxide / Q000097:blood*; D019335:Nitroarginine / Q000008:administration & dosage*; D012867:Skin / Q000098:blood supply / Q000378:metabolism; D013564:Sympathetic Nervous System / Q000502:physiology; D014665:Vasodilator Agents / Q000008:administration & dosage*
D004791:Enzyme Inhibitors; D014665:Vasodilator Agents; D019335:Nitroarginine; D009569:Nitric Oxide; D000109:Acetylcholine