CENTRAL INHIBITORY EFFECT OF ADENOSINE-DEAMINASE ON CAROTID BLOOD-FLOW INCREASE AT HIGH-PRESSURE

Carotid blood flow in rats was measured by implanted transit-time ultr asonic flowprobes throughout hyperbaric experiments conducted up to 70 bar (7 MPa) with a helium-oxygen hyperoxic (PO2 = 400 mbar) mixture. Before the hyperbaric experiment, an intracerebroventricular (ICV) inj ection of phosphate saline-buffered solution (PBS) or adenosine deamin ase (ADA, 100 U.ml(-1)) in PBS was performed. Throughout the hyperbari c experiment carotid blood flow increased with ambiant pressure in PBS -treated rats. Conversely, the increase in carotid blood flow was atte nuated by ADA treatment. These results suggest that the increase in ca rotid blood now at high ambiant pressure could result from an increase of adenosine concentration in the rat brain.