抄録
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 (14-90μm 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 (≤ 50 μm diameter) underwent marked constriction (-20% to -35%), but there were no large vessels (>50μm diameter) showed a constriction greater than -20%. Venules (17-114μm 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.
