P.1.021 Longitudinal changes of N-acetyl-aspartate in early onset psychosis

behavior compared with controls (n = 8, p< 0.01, Students t-test), indicating that they had remembered the initial FS test. No co-localization of c-Fos with BrdU was found in either group. The number of BrdU-positive neurons was higher in the dentate gyrus of the FS group (19.6±2.1 neurons, n = 8) than in control animals (12.0±1.1 neurons, n = 4) (p< 0.03, Student’s t-test). To investigate a role of GRs in the survival-promoting effect of FS we pre-treated rats with the GR antagonist RU486 before the initial FS challenge. RU486 impaired the behavioural immobility response in the 4-week retest (n = 7/group; p< 0.01, posthoc Bonferroni test) and abolished the FS-evoked increase in neuronal survival compared with the vehicle-pre-treated group (n = 5/control group, 7/FS group; p< 0.001, posthoc Bonferroni test). Thus, a single FS challenge promotes the survival of new adult-born DG granule neurons, which requires GR activation at the time of the stressful challenge and which may contribute to the formation of long-term memories of the FS event.