The effects of graded hypoxia on intraparenchymal arterioles in rat brain slices.

HYPOXIA-INDUCED changes in intracerebral arterioles, the major determinants of local cerebral oxygen delivery, are not well understood. Hippocampal arteriolar diameters were measured in rat brain slices using computerized videomicroscopy. In group 1 (control), artificial cerebrospinal fluid oxygen tension (P-O2) was maintained at 500 mmHg. In groups 2 and 3, P-O2 was gradually reduced to anoxia (95% N-2/5% CO2). In g 3, prostaglandin F-2a alpha was given to approximate physiological, myogenic tone. P-CO2 and PH were controlled. Graded hypoxia progressively dilated vessels (P-O2 300 mmHg = 2.4 +/- 1.2%, 4.2 +/- 1.6%; P-O2 90 mHg = 15.4 +/- 3.0%, 14.5 +/- 1.8%; groups 2 and 3, respectively). The presence of preconstriction did not influence the extent of hypoxia-induced dilation. This vasorelaxation may be important in maintaining cerebral oxygen delivery during microvascular hypoxia. (C) 1998 Rapid Science Ltd.