9-Amino-1,2,3,4-tetrahydroacridine (THA), an alleged drug for the treatment of Alzheimer's disease, inhibits acetylcholinesterase activity and slow outward K+ current.

The in vitro release of acetylcholine in rat brain tissue was inhibited by 9-amino-1,2,3,4-tetrahydroacridine (THA). Atropine antagonized this effect of THA. As THA does not display an affinity for muscarinic receptors, we conclude that THA inhibits acetylcholinesterase activity. In electrophysiological studies with neurons of Lymnaea stagnalis, THA inhibited the slow outward K+ current and consequently increased the duration of the action potentials. It is discussed that both effects of THA possibly contribute to its reported effect in the treatment of patients with Alzheimer's disease.