Cold exposure increases the secretion of catechol amines and enhances the effect of these hormones on metabolism. Whether the sensitivity of peripheral vessels to epinephrine and norepinephrine is altered by cold exposure has not been reported. Warm- adapted (27° ± 1° C) and cold-adapted (5° ± 1 ° C) rabbits were studied under chloralose and urethane anesthesia. Epinephrine and norepinephrine were infused (3 gamma/kg/min) through an ear vein. Rectal plus ear temperature, EKG, blood flow and venous pressure in the ear were measured. Compliance of veins was calculated from the ?V / ?P at pressures between 20 and 30 mm Hg.
After prolonged cold exposure rabbits responded to catechol amine infusion (adrenaline and noradrenaline) with less change in heart rate during infusion and a more rapid return to control levels following infusion; with less decrease in ear temperature during infusion and a more rapid return to control levels following infusion; less increase in peripheral resistance, and less effect on compliance of the capacitance vessels (veins).