The 1.5 million new cases per year of traumatic brain injury (TBI) are a significant cause of morbidity in the US. Treatment is complicated when the primary mechanical event is followed by secondary insults, resulting in reduced oxygen to the brain and exacerbation of injury. This proposal tests the hypothesis that sublethal mechanical injury sensitizes the brain to secondary injury from mild hypoxia. Using cultured organotypic hippocampal slices and a novel in vitro TBI model, the contributions of mechanical injury (acceleration) and hypoxia can be studied (Aim 1). The delay between acceleration and oxygen glucose deprivation (OGD) and the duration of OGD will define the temporal profile of secondary injury. Sensitization by acceleration will be quantified by LDH release, and injury regionally identified with PI labeling, with cell subtype determined by immunocytochemistry. Mechanisms of, and protection against, sensitization will be investigated. Methods include measurement of [Ca2+]i (Aim 2), and electrophysiologic measurements of field evoked post synaptic potentials and long-term potentiation (Aim 3). The goal is to identify novel mechanisms responsible for sensitization, expected to be critical in establishing novel neuroprotective strategies. [unreadable] [unreadable]