Glucose administration enhances memory in several amnestic populations, including old humans and rodents. The present experiment demonstrates that glucose also enhances measures of sleep in old rats. Three-hour daytime sleep EEGs were assessed in 3- and 24-month-old rats. The animals received injections of saline or glucose (100, 500, and 1000 mg/kg) on different days in a counterbalanced order. At doses of 100 and 500 mg/kg, glucose augmented the duration of paradoxical sleep bouts and total paradoxical sleep time in old, but not young, rats. Within 2 weeks after the sleep tests, measures of several brain neurotransmitter functions were obtained. Glucose was more effective in enhancing paradoxical sleep in those individual aged rats with high levels of hippocampal choline acetyltransferase and occipital cortex serotonin concentrations than in aged rats with lower levels on these neurochemical measures. The findings suggest that glucose attenuates selective age-related sleep deficits in old rats. More generally, these results add to a growing body of evidence indicating that moderate doses of peripheral glucose can influence a variety of CNS measures.
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