SN protects against MPP+-elicited DA neurodegeneration through microglia. SN (10-14 M) or MPP+ (0.2 μM) were added to the following types of cell cultures: (NG): original neuron-glial cultures; (N): neuron-enriched cultures; (N+10%MG): cultures reconstituted by adding 10% of microglia to the neuron-enriched cultures; (N+50%AS): cultures reconstituted by adding 50% of astroglia to the neuron-enriched cultures. Two and 4 days after MPP+ treatment, SN (10-14 M) was added again to the SN-treated cultures. On day 8, the MPP+-induced dopaminergic neurotoxicity was quantified by the [3H]-DA uptake assay (A), and on day 4, the release of superoxide was determined as described in Materials and methods section. Results are expressed as percentage of the vehicle-treated control cultures and represent the mean ± SE. for three independent experiments performed in triplicate. *P < 0.05, compared with MPP+ treated cultures. # P < 0.05, ## P < 0.01 compared with the vehicle-treated control cultures.