Flood_1988_J.Gerontol_43_B54

The amnesias characteristic of Alzheimer's disease and other age-related dementias are refractory to conventional pharmacotherapy. A recent treatment strategy is to combine drugs, particularly cholinergic drugs, to improve their memory enhancing effect. We previously reported that in young, weakly trained mice, the combination of arecoline and tacrine was more effective on a mg/kg basis than either drug administered alone. This was true whether the route of administration was intracerebroventricular, subcutaneous, or oral. These drug treatments have also been found to improve retention in 24-month-old mice. Mice 24 months of age show very poor recall one week after training. Failing memory must develop over time but may only be detected in mice younger than 24 months of age when the retention test interval is substantially longer. We now report that 18-month-old mice trained to avoid footshock in a T-maze show poor retention when tested two months after training and drug administration. Subcutaneous administration of arecoline, tacrine, and arecoline plus tacrine all enhanced retention of 18-month-old mice compared to the saline-injected control. The combination was as effective as the single drug treatments even though 96% less arecoline and 99.7% less tacrine were administered.