Conducted vasodilation elevates flow in arteriole networks of
hamster striated muscle.
Kurjiaka, David T., and Steven S. Segal.
The John B. Pierce Laboratory and Departments of Epidemiology &
Public Health and Cellular & Molecular Physiology, Yale University
School of Medicine, New Haven, Connecticut, 06519
APStracts 2:0222H, 1995.
Our purpose was to investigate blood flow responses to local and
conducted vasodilation in arteriole networks supplying the cremaster
muscle of anaesthetized (pentobarbital) male hamsters. We tested the
hypothesis that, with local release of a vasodilator onto an
arteriole segment, conduction is necessary to increase arteriolar
perfusion. The tips (OD, 1-2 _m) of micropipets containing ACh (1.0
M) or NP (0.2 M) were positioned 1 mm distal to the origin of a 3A
arteriole (resting diameter, 16 +/- 2 _m) originating at a
"Y" bifurcation. Responses were monitored (n=9) at the site
of release (local) and at three upstream locations: at the vessel
origin, in the parent (2A) arteriole (diameter, 24 +/- 3 _m) and in
the paired (3A) daughter branch (17 +/- 3 _m). At each upstream site,
diameter and red blood cell velocity (Vrbc) were quantified at rest
and during the peak of diameter responses; these variables were used
to calculate blood flow and wall shear rate (WSR). Microiontophoresis
(1 mA, 500 ms) of ACh increased local diameter by 13 +/- 4 _m
(p<0.05); vasodilation was conducted to each of the upstream sites
(typical magnitude, 4 to 6 _m; p<0.05). Blood flow into branches
increased 25 to 80% above corresponding values at rest without
changing Vrbc; thus, WSR consistently decreased with dilation
(p<0.05). Microiontophoresis of NP induced similar dilation locally
(segment length, 300 _m), yet had no effect on diameter, blood flow
nor WSR in network branches. Thus, dilation of a distal arteriole
segment alone had no effect on muscle blood flow. Our findings
indicate that, with local release of a vasodilator, the conduction of
vasodilation into parent and daughter branches promotes hyperemia
throughout the supplying network.
Received 11 May 1994; accepted in final form 12 May 1995.
APS Manuscript Number H406-4.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 30 May 1995.