Alzheimer's disease and THA: a review of the cholinergic theory and of preliminary results.

The cholinergic theory is based on the assumption that acetylcholine (ACh) metabolism plays an important role in memory processes and that the deterioration of memory and other cognitive functions in Alzheimer's disease (AD) is directly related to degeneration of cerebral presynaptic cholinergic neurons. This article reviews various therapeutic strategies based on this theory and particularly that of using cholinesterase inhibitors such as tetrahydroaminoacridine (THA). The few available studies--all preliminary--on THA are reviewed. They show that THA is neither a cure nor a definitive treatment for AD. However, the preliminary reports suggest for the most part a certain degree of efficacy, greater at any rate than the efficacy of other pharmaceutical agents tried so far. Despite the apparent multiplicity of pharmacological actions of THA, it appears that the cholinergic hypothesis remains valid and should be pursued further.