The Adrenergic Innervation of Arteriovenous Anastomoses in the Subcutaneous Fascia of Rat Skin

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Abstract
Stretch preparations of the subcutaneous fascia of rat trunk skin were studied using the glyoxylic acid-induced fluorescence technique for demonstrating adrenergic nerves. To facilitate the identification of blood vessels some rats were injected i.v. with a fluorescent (fluorescein isothiocyanate dextran) tracer and some stretch preparations were subsequently stained with hematoxylin and eosin. The arteriovenous anastomoses AVA were innervated with fluorescent adrenergic nerves. Several types of AVA were identified in the subcutaneous fascia of rat trunk skin: several densely innervated arteriolar branches arising from the segmental subcutaneous artery and terminating in the accompanying vein and in the capillary bed; simple arteriovenous connections with a moderately dense adrenergic innervation usually restricted to the beginning of the arteriole; and more specialized AVA which often showed a slightly tortuous or S-shaped course. They often had a dense adrenergic innervation and could occasionally be divided into a densely innervated arteriolar portion, a very densely innervated constrictory portion and an often funnel-shaped venous portion without adrenergic nerves. The control of AVA may occur via combined neural adrenergic and local regulatory mechanisms. Different tissue factors might directly influence the contractile cells of AVA and have their modulating influence on the adrenergic nervous discharge in the nerves innervating AVA. Sympathectomy or denervation during skin flap operation or an axon reflex occurring in the sensory nerves probably opens the adrenergically innervated AVA and shunts an increased quantity of blood flow through rather large mainly non-nutritive blood vessels. [The adrenergic innervation of AVA would be important for the changes in the blood flow of skin flaps which occur after surgery or in traumatic vasospastic disease.].
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