INDUCED PERIODIC HEMODYNAMICS IN SKELETAL-MUSCLE OF ANESTHETIZED RABBITS, STUDIED WITH MULTIPLE LASER-DOPPLER FLOW PROBES

Periodic fluctuations, regular slow-wave flowmotion, were induced in t he skeletal muscle of six mature anesthetized New Zealand White rabbit s by acute femoral artery pressure reduction from a median control val ue of 78 to 36 mm Hg. This phenomenon was monitored simultaneously wit h four laser Doppler flowmetry (LDF) probes placed over the gastrocnem ius muscle in a linear array with a spacing of 5 mm. The median relati ve peak-to-trough amplitude of the oscillatory flow patterns was 47%, white a frequency of approximately 2.5 cycles per minute (cpm), which remained relatively stable over an observation period of 1 h (+/- 15-2 0%). Application of two frequency analysis methods, Welch's FFT method and Prony Spectral Line Estimation yielded similar results and showed a correlation coefficient of r = + 0.84. Spectral coherence between p airs of regular slow-wave flowmotion records decreased with increasing probe separation (0.28 at 5 mm; 0.01 at 15 mm). However, patterns of frequency fluctuation over time were significantly correlated between concurrent record pairs regardless of probe separation. These results suggest that the regular slow-wave flowmotion signal originates in reg ions that are independently regulated by local vasoactive sites, which may be called pacemakers. These sites may also be influenced by an ad ditional common control mechanism, which may be myogenic/metabolic or central in nature.