Optical spectroscopy and cerebral vascular effects of alcohol in the intact brain: effects on tissue deoxyhemoglobin, blood content, and reduced cytochrome oxidase.
Dose-response effects of acute ethanol infusions were studied, noninvasively, in the unopened brain to examine the hypothesis that ethanol can induce stroke-like events as a consequence of cerebral vasospasm and tissue ischemia. By using a single sending and receiving fiber, an optical backscatter measurement (500-800 nm) was used to monitor the levels of deoxyhemoglobin (DH), reduced cytochrome oxidase (rCO), and relative tissue blood content in a closed cranium preparation. Anesthetized rats were prepared by cannulating a branch of the internal carotid artery and subjected to either bolus infusions (1.25 or 2.5 microM ethanol in Ringers/g tissue) or to constant infusions of 5 or 10% ethanol at various rates (0.30-2.92 microM/g/min). To facilitate optical penetration, a portion of the left parietal cranium was shaved to a translucent appearance. Results showed that low, bolus doses of ethanol typically produced a slight increase (5-10%) in the oxyhemoglobin signal, indicating that vasodilation had probably occurred. Higher doses, however, produced a prompt and significant reduction in the hemoglobin signal, increased levels of DH, and a rise in rCO suggesting a vasoconstrictor response leading to ischemia had occurred, followed by recovery within 3-5 min. Constant infusions of ethanol produced a similar cerebral vascular response, in a dose-related manner, but of a more sustained nature. At levels of 50-60% of the maximum bolus dose, the effect was more pronounced, accompanied by an increase in the levels of rCO (by 50-90%). Control experiments using identical volumes/flow rates of Ringers solution produced no significant alterations in the optical spectrum.(ABSTRACT TRUNCATED AT 250 WORDS)
Barbour
R L
RL
Department of Pathology, State University of New York, Health Science Center at Brooklyn 11203.
Gebrewold
A
A
Altura
B M
BM
D000435:Alcoholic Intoxication / Q000503:physiopathology*; D000818:Animals; D001810:Blood Volume / Q000187:drug effects* / Q000502:physiology; D001921:Brain / Q000098:blood supply*; D002561:Cerebrovascular Disorders / Q000503:physiopathology; D004305:Dose-Response Relationship, Drug; D003576:Electron Transport Complex IV / Q000378:metabolism*; D000431:Ethanol / Q000633:toxicity; D006454:Hemoglobins / Q000378:metabolism*; D008297:Male; D010084:Oxidation-Reduction; D051381:Rats; D017208:Rats, Wistar; D012039:Regional Blood Flow / Q000502:physiology
D006454:Hemoglobins; D000431:Ethanol; C100003:deoxyhemoglobin; D003576:Electron Transport Complex IV