Heat production and heat loss in d-amphetamine hyperthermia in aggregated Swiss Webster and BDF mice

Heat Production and Heat Loss in d-Amphetamine Hyperthermia in Aggregated Swiss Webster and BDF₁ Mice. The difference in response of aggregated Swiss Webster and BDF₁ mice to the hyperthermic effects of d-amphetamine was investigated. Heat production via motor activity and plasma free fatty acid stimulation were studied. The concentration of plasma free fatty acids in aggregated amphetaminetreated Swiss Webster and BDF₁ mice did not follow any consistent relationship with either the dose of amphetamine or the hyperthermia produced by it. Motor activity measurements also failed to show any differences that would account for the differential hyperthermia caused by amphetamine. Differences in heat production via free fatty acids and motor activity did not explain the differences in hyperthermia.Heat production was also estimated by oxygen utilization in aggregated Swiss Webster and BDF₁ mice. The indirect calorimetric oxygen utilization studies failed to show any strain difference which would account for the differences in hyperthermia. Heat loss by evaporative water loss was also measured after amphetamine administration. At room temperatures of 19° and 27°C, the BDF₁ mice were found to lose more heat through evaporation than the Swiss Webster mice after 20 mg/kg d-amphetamine sulfate. Thus, the pharmacogenetic difference in toxic and hyperthermic responses of aggregated Swiss Webster and BDF₁ mice was explained by a difference in evaporative water loss (heat loss) between the two strains.