Estimation of shear and flow rates in pial arterioles during
somatosensory stimulation.
Ngai, Al C., and H. Richard Winn.
Department of Neurological Surgery, University of Washington School
of Medicine, Seattle, Washington 98104
APStracts 2:0473H, 1995.
We tested the hypothesis that a shear stress-dependent mechanism is
involved in the dilation of pial arterioles during somatosensory
stimulation. In chloralose-anesthetized rats implanted with cranial
windows, we simultaneously measured the diameter and flow velocity of
pial arterioles with video and dual-slit methods. Stimulation (0.2
-0.3V, 5 Hz, 0.5 ms pulses for 20 s) of the contralateral sciatic
nerve evoked consistent dilator responses in pial arterioles (36 +/-
1 [mu]m diameter) without affecting blood pressure. The dilator
responses consisted of an initial transient peak dilation of 30 +/-
3%, followed by a sustained dilation of 13 +/- 1% (n=11). Mean
velocity increased by 16.4 +/- 5.7% at 5 s after stimulus onset. Wall
shear rate and volume flow were calculated from diameter and velocity
data by assuming a parabolic flow profile. There was no significant
change in wall shear rate, whereas flow rate increased significantly
during sciatic nerve stimulation. The present findings suggest that a
flow (shear stress)-mediated mechanism does not play an important
role in the dilator response of pial arterioles to sciatic nerve
stimulation.
Received 8 May 1995; accepted in final form 4 October 1995.
APS Manuscript Number H434-5.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 6 November 95