Effect of sympathetic stimulation on cerebral circulation.

The role of sympathetic regulation in cerebral circulation was studied in the cat by continuous measurement of cerebral tissue oxygen tension (BrPO2), carbon dioxide tension (BrPCO2), pH(BrpH) and blood pressure. The ipsilateral superior cervical ganglion was electrically stimulated for 3 min. A slight decrease in BrPO2 and a slight but significant increase in BrPCO2 were observed during sympathetic stimulation. These changes suggested that sympathetic stimulation slightly decreased cerebral blood flow. The present results do not rule out a significant role for sympathetic regulation of cerebral circulation. Sympathetic constriction of the extraparenchymal vessels might be compensated for by secondary dilation of the intraparenchymal vessels elicited by a chemical control (escape phenomenon).