Tetrahydroaminoacridine improves the recency effect in Alzheimer's disease

We investigated the effects of a single administration of tetrahydroaminoacridine (25 and 50 mg, orally), a cholinesterase inhibitor, on memory function in Alzheimer's disease patients. The recall of memory items from the end of the word list (recency effect) was improved in a subgroup of Alzheimer's disease patients (responders 10 out of 28) by tetrahydroaminoacridine 50 mg. However, tetrahydroaminoacridine 50 mg had no effect on the recall of those words from the beginning or middle of the list. Tetrahydroaminoacridine did not markedly improve non-verbal delayed matching to sample or paired associates learning in any of the Alzheimer's disease patients. The "responders" performed better than the "non-responders" in tests measuring memory and frontal functions. The responders had less severe hippocampal atrophy and less prefrontal blood flow defect, and had a lower frequency of the apolipoprotein E4 allele than the "non-responders". These results suggest that acute tetrahydroaminoacridine treatment may stimulate the recency effect, and that a severe dysfunction of hippocampus and prefrontal regions blocks this effect of tetrahydroaminoacridine on short-term memory performance.