Abstracts

Rationale: Previously we showed that postnatal (P) P20 rats are relatively resistant to hippocampal CA1 injury when they have a history of two earlier neonatal seizures, whereas other limbic areas are less spared. Transcriptome profiling of the CA1 subregion following single (1×KA) and multiple early life seizures (3×KA) showed many common and uncommon genes were up and downregulated. Certain anti-apoptotic and anti-inflammatory genes were exclusively upregulated in CA1 neurons after (3×KA). To gain further understanding of which genes are actually involved in spatially protective vs. neurotoxoic effects, we profiled genes of the CA3, dentate gyrus (DG), and amygdala entorhinal complex (Amg/ERcx) under similar conditions.Methods: The CA3, DG, and Amg/ERcx were isolated and total RNA was extracted, subjected to RT-PCR, and hybridized with a rat microarray platform. Several transcripts were validated with QPCR and immunohistochemistry.Results: Similar to the CA1, autophagy and pro-inflammatory genes were triggered in the CA3; however, many protective genes were also differentially upregulated, particularly after 3×KA. These included but were not limited to Ca++ modulated proteins, apoptosis inhibitors, adaptor-related protein complexes, ADAM metalloproteinases, adaptor ATG autophagy genes, caspase cascade activators, ATP-mediated gliotransmitters, GTP binding proteins, cyclins, F-box proteins, growth factors, interleukins, heat shock proteins, certain GABAergic, ionotropic and metabotropic glutamate neurotransmitter receptors and synthesizing enzymes. Differential downregulation included genes encoding ankyrin-repeat proteins, adenosine receptors, ATP synthases, caspases, Ca++ channels, certain heat shock proteins, NFKB activating proteins, synaptosomal associated proteins, K+ voltage gated channels, and zinc finger domains. In contrast, within the DG, autophagy, pro-inflammatory, pro-apoptotic, and anti-apoptotic transcripts were absent. Instead, dual specificity phosphatases that negatively regulate members of the mitogen-activated protein (MAP) kinase superfamily, axonal and vesicular motility (e.g. dynein) and ATP/ITP metabolism gene regulators predominated which likely contribute to increased Ca++ transport. Downregulated genes of the DG included ankyrins, reelin, vimentin and other adhesive and guiding transcripts, the GluR1 subunit, and several G-protein-coupled receptors. In contrast, the Amg/Ercx showed unique upregulation of cholinergic nicotinic and adrenergic receptors, and distinguished downregulation of dopamine, cholinergic muscarinic, histamine, and serotonergic receptors.Conclusions: Results indicate that sustained seizures during early life induce marked region specific brain differences in a large number of critical neurotransmitter genes that encode glutamatergic, adrenergic, chloninergic, and monomonergic receptors to influence the seizure threshold, neuronal vulnerability, proliferation and migratory domains.