INTERRELATIONSHIPS OF LOW ENVIRONMENTAL TEMPERATURES ON THE ACTIONS OF DRUGS,
TORONTO UNIV (ONTARIO) DEPT OF PHARMACOLOGY
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The effect of drugs on cold-exposed rats depends on the duration of exposure prior to treatment. Immediately after exposure to cold the albino rat increases its heat production, largely through an increase in skeletal muscle activity. Since reserpine, chlorpromazine, noradrenaline, and sodium salicylate produce a fall in the metabolic rate of these animals it might be concluded that 1 these drugs in some way inhibit heat production via shivering or 2 that an increase in thermogenesis via skeletal muscle activity is not adequate enough to offset the drug-induced hypothermia. After prolonged exposure, non-shivering thermogenesis contributes a large part of the heat requirement while the contribution due to shivering is reduced. In considering the effects of drugs on thermoregulation, or the actions of drugs at any specific ambient temperature, it appears to be necessary to have information of the effects on 1 production of heat, 2 loss of heat, 3 body temperature balance of 1 and 2, and 4 duration of action at existing body temperature. As usual, dose must be added to these variables. It is apparent that these factors are interdependent. From the work reported it is clear that any study of a drug must be carried out under specific thermal conditions, and when the drug alters the above parameters these too must be stated.
- Anatomy and Physiology