Correlation between retention of defensive conditioned reflexes and brain acetylcholinesterase activity in rats.

Abstract

1. Acetylcholinesterase activity in the motor and visual cortex and in the hippocampus of rats 1, 2, or 4 weeks after the formation of a defensive conditioned two-way avoidance reflex in the animals does not differ from the corresponding values obtained by studying the brain of animals exposed to the uncomblned action of the stimuli (active control). 2. Testing preservation of conditioned reflexes by their repeated formation 1 or 2 weeks after initial training was not accompanied by any change in acetylcholinesterase activity of the brain structures examined compared with the active control. When retention of conditioned reflexes was tested 4 weeks after their formation, a considerable decrease in acetylcholinesterase activity was found in the motor and visual cortex of the trained animals. 3. The dynamics of retention of conditioned reflexes is evidently due to changes in reactivity of the cholinergic systems of the brain with respect to stimuli used for conditioning.