This laboratory is examining the disturbances of regulatory systems involved in microcirculatory control in the brain. Microcirculatory changes following brain injury may cause secondary injury by exacerbating ischemia or hypoxia. The microcirculation and its regulation following focal ischemia or trauma are studied by the use of microelectrodes for measurement of blood flow and local oxygen tension and by microdialysis systems for measurement of excitotoxic amino acids. Another area of interest is the development of continuous brain oxygen extraction measurements for use in humans as an index of cerebral autoregulatory capacity following brain injury. The relationship between oxygen consumption and oxygen delivery becomes abnormal under certain pathological conditions. The nature of the microcirculatory disturbance that leads to this dependence is under investigation. A second goal is to identify mechanisms whereby the local chemical environment of the ventrolateral medullary chemoreceptors regulate breathing.