title: Low-frequency oscillations of the laser Doppler perfusion signal in human skin.
abstract: Spectral analysis of the laser Doppler flow (LDF) signal in the frequency interval from 0.0095-2.0 Hz reveals blood flow oscillations with frequencies around 1.0, 0.3, 0.1, 0.04 and 0.01 Hz. The heartbeat, the respiration, the intrinsic myogenic activity of vascular smooth muscle, the neurogenic activity of the vessel wall and the vascular endothelium influence these oscillations, respectively. The first aim of this study was to investigate if a slow oscillatory component could be detected in the frequency area below 0.0095 Hz of the human cutaneous blood perfusion signal. Unstimulated basal blood skin perfusion and enhanced perfusion during iontophoresis with the endothelium-dependent vasodilator acetylcholine (ACh) and the endothelium-independent vasodilator sodium nitroprusside (SNP) were measured in healthy male volunteers and the wavelet transform was computed. A low-frequency oscillation between 0.005 and 0.0095 Hz was found both during basal conditions and during iontophoresis with ACh and SNP. Iontophoresis with ACh increased the normalized amplitude to a greater extent than SNP (P = 0.001) indicating modulation by the vascular endothelium. To gain further insight into the mechanisms for this endothelium dependency, we inhibited nitric oxide (NO) synthesis with N(G)-monomethyl-L-arginine (L-NMMA) and prostaglandin (PG) synthesis by aspirin. L-NMMA did not affect the increased response to ACh vs. SNP iontophoresis in the 0.005-0.0095-Hz interval (P = 0.006) but abolished the difference in the 0.0095-0.021-Hz interval (P = 0.97). Aspirin did not affect the difference in response to ACh and SNP in either of the two frequency intervals. Thus, other endothelial mechanisms, such as endothelium-derived hyperpolarizing factor (EDHF), might be involved in the regulation of this sixth frequency interval (0.005-0.0095 Hz).
authors.affiliation: Department of Intensive Care Medicine, Ullevål University Hospital, 0407 Oslo, Norway. per.vandal@ulleval.no
authors.forename: Per
authors.initials: P
authors.lastname: Kvandal
authors.forename: Svein Aslak
authors.initials: SA
authors.lastname: Landsverk
authors.forename: Alan
authors.initials: A
authors.lastname: Bernjak
authors.forename: Aneta
authors.initials: A
authors.lastname: Stefanovska
authors.forename: Hebe Désirée
authors.initials: HD
authors.lastname: Kvernmo
authors.forename: Knut Arvid
authors.initials: KA
authors.lastname: Kirkebøen
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000328:Adult; D001120:Arginine / Q000008:administration & dosage / Q000494:pharmacology; D001241:Aspirin / Q000008:administration & dosage / Q000494:pharmacology; D001783:Blood Flow Velocity / Q000187:drug effects / Q000502:physiology; D004791:Enzyme Inhibitors / Q000008:administration & dosage / Q000494:pharmacology; D005583:Fourier Analysis; D006801:Humans; D007261:Infusions, Intra-Arterial; D007478:Iontophoresis; D017078:Laser-Doppler Flowmetry / Q000295:instrumentation / Q000379:methods*; D008297:Male; D008833:Microcirculation / Q000187:drug effects / Q000502:physiology*; D009599:Nitroprusside / Q000494:pharmacology; D012039:Regional Blood Flow / Q000187:drug effects / Q000502:physiology; D012867:Skin / Q000098:blood supply*; D014665:Vasodilator Agents / Q000494:pharmacology; D019323:omega-N-Methylarginine / Q000008:administration & dosage / Q000494:pharmacology
chemical_list: D004791:Enzyme Inhibitors; D014665:Vasodilator Agents; D009599:Nitroprusside; D019323:omega-N-Methylarginine; D001120:Arginine; D000109:Acetylcholine; D001241:Aspirin