In the present study, we examined whether cholinergic drugs such as arecoline and physostigmine attenuated an impairment of time perception presented by daily scheduled feeding in aged rats. When feeding was restricted to a single meal at a fixed time of day (13:00-17:00) for 6 successive days, young rats exhibited intense locomotor activity from 1-3 h before feeding time. Intense locomotor activity was observed between 12:00-17:00 in young animals even on the fasting day (on day 7) (mealtime-associated activity). However, this mealtime-associated activity was impaired in old rats. Daily injection of arecoline (10 mg/kg) or physostigmine (0.1 and 0.2 mg/kg) at 17:00 for 6 successive days attenuated the impairment of mealtime-associated activity on the fasting day in a dose-dependent manner in old rats, whereas daily treatment with d-glucose (100 or 2000 mg/kg) did not. The results of the present study suggest that cholinergic drugs attenuate the impairment of the manifestation of mealtime-associated anticipatory activity related to 'temporal learning' in old rats.
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