Thermally-induced cutaneous sympathetic activity related to blood flow through capillaries and arteriovenous anastomoses

Abstract

In the ears of anaesthetized rabbits cutaneous efferent sympathetic nerve activity (SkNA) and blood flow (Q) to capillaries have been measured during various thermal treatments. Warming the spinal cord or skin of the body midside caused a marked decrease in SkNA but capillary Q increased only slightly. Exposure to a warm environment or localized warming of the ear alone induced either a decrease, an increase, or no change in SkNA, but capillary Q always increased markedly. The usual slight increase in capillary Q during spinal warming, was abolished by preventing the usual marked increase in skin temperature. When the spinal cord of the conscious rat was warmed, a marked increase in temperature of the tail (which contains arteriovenous anastomoses, AVA's) indicated dilatation, whereas there was no change in ear temperature (where there are no AVA's). When these results are considered together with recently defined differential influences of reflex and direct effects of temperature on blood flow through cutaneous AVA's and capillaries, it is concluded: (1) That thermally-induced reflex changes in skin blood flow are mediated via sympathetic nervous action on AVA's; (2) Changes in blood flow evoked by direct heating take place through the capillaries, not the AVA's, quite independently of SkNA.

Pharmacological Isolation and Characterization of NMDA Receptor-Mediated Synaptic Potential in the Dentate Gyrus of Rat Hippocampal Slices

“…Prior studies also reported that sympathec tomy increased both total hindlimb blood flow and ar teriovenous anastmoses (AVA) blood flow significantly in cats and dogs (10,13). These results support the conten tion that both muscle blood vessels and AVA blood ves sels are strongly influenced by tonic sympathetic input (8,14).…”

Thermoregulation by Kangaroos from Mesic and Arid Habitats: Influence of Temperature on Routes of Heat Loss in Eastern Grey Kangaroos (Macropus giganteus) and Red Kangaroos (Macropus rufus)

“…Peripheral vasoconstriction in the heat has been reported for numerous arid-inhabiting mammals and birds since it was first reported in the antelope jackrabbit (Lepus alleni; Schmidt-Nielsen et al 1965;Dawson and Schmidt-Nielsen 1966). The mechanisms involved in such vasomotor adjustments have largely been uncovered by the studies of Hales and coworkers (Hales et al 1978a(Hales et al , 1978bHales and Fawcett 1979).…”

Blood flow in the diabetic neuropathic foot

“…They have a rich innervation which is primarily under the control of the sympathetic system although digital arteriovenous anastomoses also possess a cholinergic innervation [13]. Thermally induced reflex changes in skin blood flow are mediated via sympathetic nervous action on the arteriovenous anastomoses [14] and one would expect arteriovenous shunts to open following sympathetic denervation.…”