The role of brain stem vasomotor centers in the neurogenic control of cerebrovascular tonus

Abstract

This experiment was designed to clarify the neurogenic control of the dorsomedial nucleus of the hypothalamus (DM), the reticular formation of the midbrain (MBRF), and the reticular formation of the medulla oblongata (MORF) on cerebrovascular tonus. Using 56 cats, electrodes were inserted into the DM, MBRF, and MORF, the latter stimulated, and the vasomotor centers subsequently coagulated with the lesions in the DM and MBRF enlarged. The effect of increasing the number of lesions coagulated simultaneously was also examined. The MORF was stimulated just after the DM and MBRF were coagulated simultaneously. Blood pressure (BP), intracranial pressure (ICP), and cerebral blood volume (CBV) were continuously measured. A transient decrease in BP and increases in ICP and CBV were observed at insertion. Simultaneous increases in BP, ICP, and CBV were induced by stimulation. Temporary decrease in BP and increases in ICP and CBV were observed with coagulation in the DM and MBRF. Transient increases in BP, ICP, and CBV were induced by coagulation of the MORF. Increasing the size and number of lesions led to changes in BP, ICP, and CBV being magnified. The combination of MORF stimulation and coagulation of DM and MBRF also increased ICP transiently. These results suggested that the areas stimulated and/or coagulated in the DM, MBRF, and MORF play an important role in decreasig cerebral vasomotor tonus.