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Department of Molecular Physiology and Biological Physics, University of Virginia Health Sciences Center, Charlottesville, Virginia 22906-0011
In rat cremasteric
microcirculation, mechanical occlusion of one branch of an arteriolar
bifurcation causes an increase in flow and vasodilation of the
unoccluded daughter branch. This dilation has been attributed to the
operation of a shear stress-dependent mechanism in the
microcirculation. Instead of or in addition to this, we hypothesized
that the dilation observed during occlusion is the result of a
conducted signal originating distal to the occlusion. To test
this hypothesis, we blocked the ascending spread of conducted vasomotor
responses by damaging the smooth muscle and endothelial cells in a
200-µm segment of second- or third-order arterioles. We found that a
conduction blockade eliminated or diminished the occlusion-associated
increase in flow through the unoccluded branch and abolished or
strongly attenuated the vasodilatory response in both vessels at the
branch. We also noted that vasodilations induced by ACh
(10
4 M, 0.6 s) spread to, but not beyond, the area
of damage. Taken together, these data provide strong evidence that
conducted vasomotor responses have an important role in coordinating
blood flow in response to an arteriolar occlusion.
gap junctions; flow dependent; arteriole; acetylcholine; ischemia
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