THE EFFECTS OF EXERCISE AND LIMITATION OF MOVEMENT ON AMPHETAMINE TOXICITY

Abstract

The effects of forced exercise and limitation of movement on the toxicity of amphetamine in isolated, aggregated and closely grouped or crowded mice were studied at environmental temperatures of 20°, 26°, and 32°C.

In general, within the temperature range of this study, elevation of environmental temperature increased amphetamine toxicity. Aggregation effect was noted only at a temperature of 26°C but at this temperature crowding together of animals whose physical movements were limited to a small area did not produce an increase in drug effect comparable to that of aggregation. Forced exercise produced an increase in drug toxicity at 20°C, at which temperature animals not forceably exercised tended to be relatively inactive. At 26° the effect of forced exercise on isolated animals was as great as the effect of "aggregating" animals. At 32°C animals whose movements were restricted to a small area were less susceptible to amphetamine toxicity than animals free to move in larger areas or forced to exercise. At this temperature when the motor activity of the mice was limited to a small area, those that were closely crowded together were more susceptible to the drug than isolated animals. Since a rapidly moving stream of air at ambient temperature eliminated the effect of aggregation at 26°C, and the effect of grouping in close proximity at 32°C, and since forced exercise increases amphetamine toxicity as much as aggregation at 26°C, it is possible that "aggregation effect" may be due, at least in part, to an increase in body temperature resulting from an increase in the motor activity of aggregated mice. It would thus appear that factors which increase heat production or decrease heat loss tend to increase amphetamine toxicity.