PEA decreases astrocyte activation in organotypic cultures of rat hippocampi and rescues neuronal CA3 damage caused by Aβ challenge. Aβ-challenged (1 μg/ml) slices of rat hippocampi were treated for 24 hours with PEA (0.1 μM) in the presence of the selective PPARγ antagonist (GW9662, 9 nM) or the selective PPARα antagonist (MK886, 3 μM). (A) Nissl staining showing the effect of treatment on the morphology of organotypic hippocampal slices. Scale bar: 80 μm. Aβ caused a marked neuronal loss, mainly in the CA3 region of hippocampus, as highlighted by arrows. PEA was able to reverse this effect. (B) Representative photomicrographs of the CA3 region showing the results of immunofluorescence experiments aimed at investigating the effect of treatments on astrocyte activation and neuronal loss, as determined by immunostaining for GFAP (green) and MAP2 (red) alone or merged, respectively. Nuclei were stained with Hoechst (blue). Scale bar: 10 μm. Arrows in the photomicrographs indicate astrocyte infiltration events and apoptotic condensation in the nuclei of adjacent neurons. (C) Relative quantification of GFAP-positive cell number as a count of astrocyte proliferation. (D) Apoptotic events detected on MAP2-expressing cells as an indication of neuronal death. For (C) and (D), the average value was determined by counting cells in at least five microscopic fields for each treatment. Results are presented as means ± SEM of four separate experiments. At least four slices from each experimental group were observed for each experiment. Statistical analysis was performed using parametric one-way analysis of variance, and multiple comparisons were performed using the Bonferroni test. ***P < 0.001 and *P < 0.05 vs. control; ∘∘
P < 0.01 and ∘
P < 0.05 vs. Aβ-challenge slices.