GABAERGIC SYNAPTIC CURRENT IN DISSOCIATED NUCLEUS BASALIS OF MEYNERT NEURONS OF THE RAT

gamma-Aminobutyric acid (GABA)-mediated spontaneous inhibitory postsynaptic currents (IPSCs) were recorded from dissociated rat nucleus basalis of Meynert neurons which still had their synaptic boutons attached. The membrane currents were recorded by the whole-cell patch-clamp technique. Elevated extracellular K+ concentration and the addition of the calcium ionophore, A23187, enhanced the amplitude and frequency of spontaneous IPSCs. Ryanodine and Ca2+-free external solution containing EGTA or BAPTA markedly decreased the spontaneous IPSC activities. Spontaneous IPSC activities were reversibly reduced by baclofen and increased by phaclofen, indicating that the GABA(B) receptor regulates the release of GABA from nerve terminals and acts as a negative autoreceptor.