This project focuses upon the role of hydrostatic pressure gradients in the formation and resolution of brain edema in experimental animals. We intend to show that edema formation associated with cold injury and with hydrocephalus, depends upon intracranial pressure gradients and that one may be controlled by manipulating the other. This study will test the validity of the hypothesis that a hydrostatic gradient is the fundamental pathophysiologic process in both vasogenic and interstitial edema. Acute and chronic experiments will employ cold injury of the brain, communicating hydrocephalus, and their combination. The edema wave created by each edemogenic process will be studied for tissue water and electrolytes, and for distribution of labelled albumin injected into the CSF or blood. In addition, intracranial pressure gradients between the cortical surface and the lateral ventricle will be measured during the progressive phase of hydrocephalus in awake animals to determine the role of a transcerebral mantle pressure gradient in that disorder.