DIFFERENTIAL EXCITOTOXIC VULNERABILITY OF HIPPOCAMPAL CA1 AND CA2 NEURONS IN RELATION TO POLYAMINE DYNAMICS

Excitotoxic neuronal death is a central mechanism in neurological disorders, although the hippocampus exhibits marked regional differences, with pronounced vulnerability of CA1 neurons and relative resistance of the CA2 region. In this study, we investigated whether distinct patterns of polyamine (PA) metabolism may contribute to this divergent sensitivity. We exposed rat organotypic hippocampal slice cultures to 25 microM NMDA to reproduce disease-relevant excitotoxic injury, and observed extensive damage in CA1 while CA2 neurons were significantly less affected. LC-MS profiling revealed that NMDA exposure significantly depleted ornithine, a key precursor of PA synthesis, as well as putrescine, spermidine, spermine, while N1-acetylspermine, whereas arginine and N1-acetylspermidine levels remained unchanged. To assess the functional relevance of PA metabolism, we inhibited spermine synthase using APCHA. APCHA alone was non-toxic at all tested concentrations, whereas it reduced NMDA-mediated neuronal death in a dose-dependent manner. A concentration of 1 mM was selected for further experiments as it almost completely abolished NMDA-induced damage in CA2 while providing only a modest protection in CA1. This regional protection was reversed by co-application of 100 microM spermine, which exacerbated neuronal death in both CA1 and CA2. Together, these findings support a role for PA homeostasis in shaping regional hippocampal neuronal vulnerability to excitotoxic neuronal death. This work was supported by: National Science Centre grant no. 2023/49/N/NZ4/02660.