Effects of cholinergic drugs and cerebral metabolic activators on memory impairment in old rats.

Age-related changes in the acquisition and retention of memory based on the step-through active avoidance response were studied in rats and the effects of cholinergic drugs and cerebral metabolic activators on memory impairment in old rats were also tested. Six- and 12-month-old rats showed lower rates of acquisition of the active avoidance response than did 2-month-old rats. In addition, the retention of the active avoidance response in 6- and 12-month-old rats diminished rather rapidly compared with that observed in 2-month-old rats. Intraventricular injection of acetylcholine at doses of 20 and 50 ng caused a significant improvement of memory impairment in old rats. Physostigmine and arecoline also caused a significant ameliorating effect at doses of 0.02 and 0.05 mg/kg i.p. and 0.2 and 0.5 mg/kg i.p., respectively. Hopantenate calcium (100 mg/kg, p.o.), idebenone (20 and 50 mg/kg, i.p.), indeloxazine (50 mg/kg, p.o.) and DM-9384 (30 mg/kg, p.o.) also proved useful to improve memory impairment in old rats.