EMBRYONIC rat hippocampal neurons were cultured on poly D-lysine (PDL) or on cortical astrocytes, some of which had been pretreated for 2 4 h with amyloid β-protein (β-AP). Amino acid-induced currents were quantified. Membrane capacitance (Cm), as well as the amplitude and density of amino acid-evoked currents recorded in neurons cultured on untreated astrocytes were all statistically greater than those recorded in neurons grown on PDL. However, compared to untreated astrocytes, those treated wit h β-AP led to significantly lower values in neurons for Cmand GABA, kainate- and NMDA-induced currents, while glycine-activated current values were not significantly different. Furthermore, β-AP treatment abolished spontaneous Cac2+fluctuations in astrocytes, which may account for their impaired ability to promote the expression of functional transmitter receptors in neurons.