Acute Brain Injury, Mechanisms and Consequences

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DESCRIPTION (Adapted from applicant's abstract): This is an application to support studies aimed at clarifying the role(s) of excitotoxic and /or apoptotic cell death mechanisms in developmental (perinatal) brain injury associated with head trauma and hypoxia/ischemia. In addition to addressing these aims during the application period, the investigator has made the unanticipated discovery that during the synaptogenesis period of development transient ethanol intoxication triggers a massive wave of apoptotic neurodegeneration, deleting millions of neurons from many different regions of the developing rat, mouse, or guinea pig brain. Our findings document that ethanol triggers apoptosis by a dual mechanism - blockade of NMDA glutamate receptors and excessive activation of GABAA receptors. We propose that our findings can help explain the reduced brain mass and lifelong neurobehavioral disturbances associated with the human fetal alcohol syndrome (FAS). Significance of this discovery is broadened by accompanying evidence that ethanol's neurotoxic properties are shared by numerous other agents that either block NMDA glutamate receptors or activate GABAA receptors, and many of these agents are drugs of abuse and/or are used regularly in obstetric and pediatric medicine. An important feature of our findings is that within the synaptogenesis period (first 2 weeks after birth for rats and mice, but third trimester and first several years after birth for humans) different neuronal populations have different temporal patterns for responding to the apoptosis-inducing effects of these drugs. Thus, depending on the timing of exposure, different combinations of neuronal groups will be deleted.