Vascular response to hyperoxemia in rat brain surface microvessels.
The effects of hyperoxemia on pial vessel diameters were studied in rats using a cranial window technique. The brain surface was superfused with mock cerebrospinal fluid at 5 ml/hr, and the intracranial pressure was maintained at 5 mmHg. Animals were artificially ventilated, and the arterial carbon dioxide tension was constantly controlled in each animal. Arterioles (14-90 microns diameter during air inhalation) constricted significantly according to the arterial oxygen tension (PaO2) increase: 94 +/- 7% (30% O2), 91 +/- 8% (60% O2), and 88 +/- 8% (100% O2). The percentage diameter change per mmHg PaO2 increase was 0.1% under normoxemia, but became less under hyperoxemia (0.025% and 0.01% per mmHg during 30%-to-60% and 60%-to-100% O2 inhalations, respectively). The diameter change between 60% and 100% O2 inhalations was not significant. There was no significant relationship between the vascular response and the control diameter. Some small arterioles (< or = 50 microns diameter) underwent marked constriction (-20% to -35%), but there were no large vessels (> 50 microns diameter) showed a constriction greater than -20%. Venules (17-114 microns diameter) did not have a significant response to hyperoxemia. The vasoconstriction of pial arterioles was proportional to arterial O2, but the relationship was not linear.
Kawamura
S
S
Department of Surgical Neurology, Research Institute for Brain and Blood Vessels-AKITA.
Yasui
N
N
D000818:Animals; D002560:Cerebrovascular Circulation; D008297:Male; D008833:Microcirculation; D010100:Oxygen / Q000097:blood*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014666:Vasomotor System / Q000503:physiopathology*
D010100:Oxygen