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

Staunton, Michael1; Dulitz, Michael, G.1; Fang, Celia1; Schmeling, William, T.1,2,5; Kampine, John, P.1,3; Farber, Neil, E.1,2,4,6

Neurophysiology

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 (PO2) was maintained at 500 mmHg. In groups 2 and 3, PO2 was gradually reduced to anoxia (95% N2/5% CO2). In group 3, prostaglandin F2a α was given to approximate physiological myogenic tone. PCO2 and pH were controlled. Graded hypoxia progressively dilated vessels (PO2 300 mmHg = 2.4±1.2%, 4.2 ± 1.6%; PO2 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.

1Department of Anesthesiology, The Medical College of Wisconsin, Children's Hospital of Wisconsin, MEB, 462C, 8701 Watertown Plank Rd., Milwaukee, WI 53226

2Departments of Pharmacology and Toxicology, The Medical College of Wisconsin, Children's Hospital of Wisconsin, MEB, 462C, 8701 Watertown Plank Rd., Milwaukee, WI 53226

3Department of Physiology, The Medical College of Wisconsin, Children's Hospital of Wisconsin, MEB, 462C, 8701 Watertown Plank Rd., Milwaukee, WI 53226

4Department of Pediatrics, The Medical College of Wisconsin, Children's Hospital of Wisconsin, MEB, 462C, 8701 Watertown Plank Rd., Milwaukee, WI 53226

5The Zablocki Veterans Affairs Medical Center, Milwaukee, WI, USA

6Corresponding Author and Address: Neil E. Farber, Department of Anesthesiology, The Medical College of Wisconsin, Children's Hospital of Wisconsin, MEB, 462C, 8701 Watertown Plank Rd., Milwaukee, WI 53226

ACKNOWLEDGEMENTS: The authors wish to sincerely thank Dr Antal G. Hudetz for helpful comments and suggestions and David A. Schwabe for expert technical assistance in all facets of this investigation. Supported in part by NIH RO1 Grant #GM56398-01 (N.E.F.) and by the Foundation for Anesthesia Education and Research, Ohmeda and the Society for Pediatric Anesthesia (N.E.F.).

Received 8 January 1998; accepted 1 March 1998

© Lippincott-Raven Publishers.