ARTERIAL VASOMOTION - EFFECT OF FLOW AND EVIDENCE OF NONLINEAR DYNAMICS

Vasomotion has been studied on segments of rat mesenteric and femoral arteries perfused in vitro. We have investigated 1) the effect of perf usion from on the characteristics of vasomotion and 2) the nature and patterns of vasomotion. We have found that perfusion flow is not a con trol parameter that contributes to the genesis of vasomotion but that it affects, in most cases only slightly, the frequency and amplitude o f vasomotion. We have found evidence that vasomotion is low-dimensiona l chaotic. The correlation dimension ranged between 2 and 4, and the a verage Lyapunov's coefficient was similar to 0.1. A great variety of v asomotion patterns was observed with features that are typical of nonl inear deterministic systems: regular and irregular vasomotion, quasipe riodicity, period doubling and higher-order periods, intermittency, mi xed modes, and bursting activity. Vasomotion patterns appeared occasio nally to be highly sensitive bo perturbations in perfusion flow, which also supported the existence of nonlinear dynamics. Finally, entrainm ent (phase locking) was observed when arteries were perfused with osci llatory flow with frequency in the neighborhood of the frequency of va somotion.