Suppression of microglial neurotoxicity by DCKA and DAAOx. Primary microglia were treated for 24 h in the absence (Con) or presence of 15 μM Aβ1–42 (Aβ). The conditioned medium from these cultures was then diluted four-fold into the medium of primary hippocampal neuron cultures; neuronal viability was measured 24 h later by LDH release. Some neuronal cultures received simultaneous application of 1 or 10 μM DCKA, and additional sets were exposed to microglia-conditioned medium that had been pre-treated with DAAOx. Values represent the mean ± SEM of triplicate determinations, and the results are representative of three experiments (*p < 0.01 versus "no drug, +Aβ"). Similar data were obtained using MTT reduction as an index of viability.