Tetrahydroaminoacridine blocks voltage-dependent ion channels in hippocampal neurons

Tetrahydroaminoacridine (THA) is a centrally active anticholinesterase that may produce functional improvement in patients with Alzheimer's disease. Because of its structural similarity to the potassium channel (A-current) blocking drug 4-aminopyridine (4-AP), it has been speculated that some of the therapeutic benefit of THA might result from inhibition of potassium currents. In the present study, THA produced a dose-dependent, reversible block of the A-current in cultured hippocampal neurons (IC50, 30 microM). However, at similar concentrations it also inhibited other voltage-dependent currents.