Impaired learning of active avoidance in water-intoxicated rats.

Brain edema is an important clinical condition. Pathophysiological findings on behavioral changes may be helpful for a comprehensive understanding of brain edema. However, only few reports on behavioral studies of brain edema have so far appeared. Experiments using psychological techniques on animals are rather time-consuming and may not be suitable for the study of transient conditions, as brain edema caused by trauma, vascular accidents, or others. We have developed a method for avoidance learning of rats using a running wheel apparatus with computer assistance. This model was employed in studies on brain edema from water introxication in rats. As a result, avoidance learning was significantly impaired by water intoxication. Either direct overhydration of the brain or indirect effects, as a decrease in cerebral blood flow, or both, are suggested as mechanisms underlying the impairment of behavior.