Cutaneous Venoconstrictor Response to Local Cooling in the Dog

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Abstract
Studies were performed in dogs to determine if inhibition of neuronal reuptake of norepinephrine was the cause of the enhanced response to sympathetic nerve impulses seen in the cutaneous veins when the temperature of the blood perfusing them was decreased. Changes in driving pressure of the saphenous vein perfused with blood at constant flow were used to measure venomotor responses. The increases in venoconstrictor response to norepinephrine infusion caused by cooling the perfusate were similar in both hindlegs, one subjected to acute and the other to chronic sympathectomy. Blocking the reentry of norepinephrine into the sympathetic nerve endings by treating the vein with cocaine did not affect the augmentation by local cooling of the constrictor response to norepinephrine or electric stimulation of the lumbar sympathetic chain. The venoconstrictor responses to norepinephrine, epinephrine, 5-hydroxytryptamine, and molar potassium chloride were all augmented by local cooling. The results suggest that the sensitizing effect of cold on the smooth muscle of the veins cannot be explained by inhibition of norepinephrine re-uptake by the nerve terminals.