Hypoxia and Spontaneous Locomotor Activity in the Rat

Abstract

Three experiments investigated the effects of hypoxia on activity wheel running in male Sprague-Dawley rats. Ss were exposed to atmospheres containing 21% O2 (normoxia), 16% O2, 12% O2, and 8% O2 for 20 min. of running. Decreases in activity occurred in atmospheres below 16% O2. Activity over the length of each 20-min. running period decreased as a function of amount of previously elapsed running time but was not significantly affected by the duration of previous exposure to the experimental atmosphere. Running in a normoxic atmosphere was increased if the immediately preceding exposure involved a hypoxic rather than normoxic atmosphere. The results suggest a dual effect of hypoxia. Hypoxia initially increases the tendency to be active in the non-running rat but eventually reduces activity in the running animal. Hypoxia was compared to other deprivation states with respect to motivational properties.