Responses of Cold- and Warm-Adapted Dogs to Infused Noradrenalin and Acute Body Cooling

摘要

A total of 12 experiments was done in cold-adapted (C-A) and warm-adapted (W-A) beagle dogs, kept more than 40 days at -10 C and 28 C, respectively. The animals, anesthetized with pentobarbital sodium were paralyzed with Flaxedil (5 mg/kg/hour) and mechanically ventilated at 28-30 C. Oxygen consumption, heart rate and colonic, pinna and paw skin temperatures were measured continuously. The dogs were infused with noradrenalin for 20 minutes at 30 C and after 45 minutes of acute cold exposure to 5 C. At 28-30 C, basal oxygen consumption was higher in C-A dogs. Oxygen consumption of C-A dogs increased with a slight increase in the heart rate during the initial 18-20 minutes after body cooling and then decreased. In W-A dogs, oxygen consumption decreased continuously after acute cold exposure. Calorigenic effects of infused noradrenalin were consistent in C-A and W-A dogs at 30 and 5 C, but there was no difference between the increased amount of oxygen consumption from the initial levels in both groups. Nor-adrenalin caused an increase of the heart rate in W-A dogs at 30 and 5 C, with decrease or no change in C-A dogs. Colonic, pinna and paw skin temperatures were significantly higher in C-A than in W-A dogs. Noradrenalin caused an increase in the temperatures, but the effect of the drug was more prominent in W-A than in C-A animals at lower temperature. (Author)