The effect of disturbance of cerebral venous drainage on acute ischemic cerebral edema and cerebral circulation were studied by measuring local cerebral blood flow (LCBF) and local changes in brain water content using a middle cerebral artery (MCA) occlusion model. Rats were anesthetized with halothane and the stem of the left MCA was occluded. Disturbance of cerebral venous drainage was induced by bilateral occlusion of the external jugular veins, i.e., the right external jugular vein was cannulated and the left one was occluded by a clip. LCBF was measured by the 14C-iodoantipyrine (14C-IAP) autoradiographic method at 2 hours after MCA occlusion. Local changes in brain water content were studied 2 hours after MCA occlusion by measuring the specific gravity of cerebral tissue in the gradient column with bromobenzene and kerosene. The control rats which underwent the same anesthesia and surgical procedure including the MCA occlusion and cannulation into the right external jugular veins, but which did not undergo occlusion of the left external jugular veins, were prepared and studied at the same time after MCA occlusion. In the rats with bilateral occlusion of the external jugular veins, the external jugular venous pressure was evaluated up to about 8 mmHg (100 mmH2O) (control: 1.3 mmHg). At 2 hours after MCA occlusion, LCBF in the ischemic core was decreased. The ischemic area was more extensive in the rats with bilateral occlusion of the external jugular veins compared with the controls. Furthermore, specific gravity of the brain was decreased in the entire left MCA territory in the rats with bilateral occlusion of the external jugular veins.(ABSTRACT TRUNCATED AT 250 WORDS)