Inhibitory effect of 1,2,3,4‐tetrahydro‐9‐aminoacridine on the depolarization‐induced release of GABA from cerebral cortex

1,2,3,4‐Tetrahydro‐9‐aminoacridine (THA) has an inhibitory effect on the activity of acetylcholinesterase which has led to its use in the treatment of Alzheimer's disease. Other actions of THA include the inhibition of voltage‐dependent ion channels. In this paper we describe the effect of THA on the depolarization‐induced release of [14C]‐γ‐aminobutyric acid (GABA) from tissue slices of rat cerebral cortex. THA produced a dose‐dependent inhibition of the 30mM K+‐evoked release of [14C]‐GABA with an IC50 of 56 μm. The maximal response was an 84% inhibition of the evoked response. THA (up to a concentration of 1 mm) had no effect on the basal release of GABA. A similar inhibitory effect on the K+‐evoked release of [14C]‐GABA was seen with 4‐aminopyridine (4‐AP) but no inhibition was obtained with tetraethylammonium up to a concentration of 20 mM. The maximal inhibitory effect of 4‐AP (39%) occurred at 1mM (IC50 of 112 μm) and this response was much smaller in magnitude than that obtained with THA.