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 the skeletal muscle of six mature anesthetized New Zealand White rabbits by acute femoral artery pressure reduction from a median control value of 78 to 36 mm Hg. This phenomenon was monitored simultaneously with four laser Doppler flowmetry (LDF) probes placed over the gastrocnemius muscle in a linear array with a spacing of 5 mm. The median relative 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 (+/- 15-20%). 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 pairs 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 regions that are independently regulated by local vasoactive sites, which may be called pacemakers. These sites may also be influenced by an additional common control mechanism, which may be myogenic/metabolic or central in nature.