A dose-dependent increase of Tau immunostaining is produced by glutamate toxicity in primary neuronal cultures.

Neuronal degeneration was produced in primary cultures by glutamate exposure and the modifications of Tau immunoreactivity were analysed in degenerating neurons. After 8-12 days of culture, glutamate was applied at different concentrations (50, 100, 200 and 500 mumol) in a Na(+)- and Mg(2+)-free solution containing calcium. Prior to and 12 hours after glutamate exposure cell death was defined by cell counting in each dish. After fixation, neurons were processed for immunocytochemistry using a Tau2 monoclonal antibody and a Tau polyclonal antibody (Sigma). Tau immunostaining was scored by a blind count of immunoreactive cells and a semi-quantitative evaluation. The results show that the number of labelled neurons and the magnitude of neuronal immunolabelling are both related to the glutamate concentration. Our findings indicate that glutamate induces a dose-dependent increase of Tau immunoreactivity directly related to its cellular action on neuronal cells.