Glucose-enhanced performance by aged rats on a test of conditional discrimination learning

Abstract

Groups of normal old rats and young adult rats were administered a test of conditional discrimination learning (CDL) with variable intervals between stimulus presentation and response selection. Previous work with this task showed that CDL acquisition depends on frontal-lobe involvement, whereas the ability to recall conditional stimuli at relatively long intervals requires an intact hippocampus. Old rats were slower to learn the CDL habit and their impairment increased with the length of the stimulus—response interval. Peripheral injections of glucose (100 mg/kg) improved performance of old rats at delays of 5 and 15 sec, but had no effect in the 0-sec delay condition. Young rats did not respond to glucose treatment. The enhancing effects of glucose in the old group were found to correlate positively with measures of glucose metabolism. The results provide evidence that glucose-induced attenuation of cognitive loss in old rats is especially pronounced for specific memory function under hippocampal control. © 1995, Psychonomic Society, Inc.. All rights reserved.