THA improves word priming and clonidine enhances fluency and working memory in Alzheimer's disease

We investigated the effects of a single administration of a cholinesterase inhibitor, tetrahydroaminoacridine (THA, 25 and 50 mg, orally), and an alph a(2)-agonist, clonidine (0.5 and 2 mu g/kg, orally), on neuropsychologic pe rformance in two groups of patients with Alzheimer's disease (AD). Clonidin e enhanced a spatial working memory and verbal fluency, but had no effect o n spatial span or word priming. THA enhanced word priming, but had no effec t on other performance measures. Our data suggests that degeneration of the LC noradrenergic system and the cholinergic cells of the basal forebrain h ave different functional consequences during the progression of AD. Finally , a combined treatment with noradrenergic and cholinergic drugs might produ ce a qualitatively broader effect on cognitive functions than either of the treatments alone, and more effectively attenuate clinical dementia. [Neuro psychopharmacology 20:357-364; 1999] (C) 1999 American College of Neuropsyc hopharmacology. Published by Elsevier Science Inc.