EFFECTS OF NORADRENALINE AND CARBACHOL ON TEMPERATURE REGULATION OF COLD‐STRESSED AND COLD‐ACCLIMATED RATS

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Abstract
1 Noradrenaline (20 μg) and carbachol (1 μg) injected into the anterior hypothalamus of rats at an ambient temperature of 23°C evoked significant falls in core temperature and increases in tail temperature. 2 When rats were cold-stressed (4°C for 90 min) or cold-acclimated (4°C for 4 weeks) and the above amine injections repeated, only carbachol evoked significant falls in core temperature and neither amine increased tail temperature. 3 Central injections of noradrenaline and carbachol also evoked increases in plasma glucose concentrations but not plasma non-esterified fatty acid (NEFA) concentrations in control, acutely cold-stressed and cold-acclimated rats. 4 Although concentrations of plasma glucose and blood lactate of rats were unaffected by cold exposure to 4°C for 1 to 28 days, glucose oxidation rate of both cold-stressed and cold-acclimated rats was significantly greater than in rats at 23°C. Concentrations of plasma NEFA were increased after 1 to 28 days of cold exposure.