AJP - Heart and Circulatory Physiology, Vol 271, Issue 5 2007-H2013, Copyright © 1996 by American Physiological Society
Control of arteriovenous anastomoses in rabbit ear model of digital perfusion
D. C. Pollock, Z. Li, L. A. Koman, E. S. Gordon and T. L. Smith
Department of Orthopaedic Surgery, Bowman Gray School of Medicine of Wake Forest University, Winston-Salem, North Carolina 27157-1070, USA.
The arteriovenous anastomoses (AVA) of the cutaneous microcirculation of
the hands and feet are fundamental determinants of thermoregulatory blood
flow and may be involved in cold intolerance. These direct microvascular
studies are an initial characterization of adrenergic receptor subtypes
participating in control of AVA in the ears of anesthetized male New
Zealand White rabbits. Adrenergic alpha 1-stimulation with phenylephrine
produced AVA constriction, whereas terazosin (an alpha 1-antagonist)
produced dilation and attenuated the responses to phenylephrine. Adrenergic
alpha 2-stimulation with UK-14304 produced constriction of the AVA, whereas
atipamezole (an alpha 2-antagonist) produced dilation and attenuated the
responses to UK-14304. When equimolar concentrations of antagonists were
studied, the AVA dilation produced by alpha 2-blockade was greater than
that produced by alpha 1-blockade. Norepinephrine (a mixed alpha 1- and
alpha 2-agonist) also produced vasoconstriction, which was attenuated by
both prazosin (an alpha 1-antagonist) and atipamezole. In summary, 1) AVA
contain a heterogeneous mixture of both alpha 1- and alpha 2-receptors, and
2) alpha 2-receptors may have a greater influence than alpha 1-receptors on
overall tone in AVA.
