EFFECTS OF INTRACEREBROVENTRICULAR ADMINISTRATION OF AMINOPHYLLINE ONHYPERBARIC INDUCED INCREASE IN CAROTID BLOOD-FLOW

Carotid blood flow was measured in rats by implanted transit-time ultr asonic flowprobes during hyperbaric experiments at up to 70 bar (7 MPa ) using an helium-oxygen hyperoxic (partial pressure of O-2 = 400 mbar ) mixture. Before the hyperbaric experiment, an intracerebroventricula r injection of phosphate saline buffered solution (PBS) or aminophylli ne, an adenosine receptor blocker, in PBS was given. Throughout the hy perbaric experiment carotid blood flow increased with ambient pressure in both PBS, i.e. control, and aminophylline treated rats. The increa se in carotid blood flow was significantly attenuated in aminophylline treated rats. Additional experiments showed that the increased caroti d blood flow was independent of hyperoxia as well as of temperature. T he hypothesis that the hyperbaric dependent increase in carotid blood flow was mediated by brain adenosine receptors and its implication reg arding a cerebral vasodilatation are discussed.