Mouse astrocytes were prepared from the cortex of postnatal day 1 (P1) BL6 mice, after treatment with Trypsin/EDTA (PAA, Pasching, Austria). The astrocytes were washed with prewarmed DMEM (37°C, PAA) and transferred to DMEM containing 2 mM l-glutamine, penicillin and streptomycin and 10% fetal bovine serum (PAA). Cells were cultured in a humidified incubator at 95% air and 5% . One day prior to hippocampi preparation, astrocyte growth was blocked with mitomycin (Sigma-Aldrich, Deisenhofen, Germany) for 1.5 h followed by washing with DMEM (PAA) and cultivation in DMEM supplemented with 2 mM l-glutamine, penicillin and streptomycin, and 10% fetal bovine serum (PAA). Prior to preparation of the hippocampi, the astrocytes were transferred to prewarmed Neurobasal medium (Invitrogen, Darmstadt, Germany) containing B27 supplement (Invitrogen), 2 mM l-glutamine (PAA), penicillin (PAA), and streptomycin (PAA).