&p.1:Abstract Different times of incomplete cerebral isch- emia (2, 4, 6, 8, 10 and 30 min) were induced by bilater- al common carotid artery occlusion in anesthetized rats to evaluate the time course of changes in lipid peroxida- tion and energy metabolism. Analysis of malondialde- hyde (used to assess the levels of lipid peroxidation), as- corbic acid, oxypurines, nucleosides, nicotinic coen- zymes and high-energy phosphates, was carried out by high-performance liquid chromatography on neutralized perchloric acid extract of brain tissue. Under the present experimental conditions, malondialdehyde, nicotinic co- enzymes and ATP catabolites (oxypurines and nucleo- sides) were affected by increasing times of ischemia, with respect to control sham-operated rats. In particular, the concentration of malondialdehyde, undetectable in control brains, increased from 1.26 nmol/g wet weight after 2 min of carotid clamping to 13.42 nmol/g wet weight at the end of 30 min of incomplete cerebral isch- emia. The presence of oxidative stress was further sup- ported by ascorbic acid depletion, which was particularly significant after 10 and 30 min of incomplete ischemia. Carotid clamping provoked an imbalance between ener- gy production and consumption that was evidenced by a reduction in ATP and GTP concentrations and an in- crease in ATP degradation products such as AMP, oxyp- urines and nucleosides. A decrement in the sum of ade- nine nucleotides and the energy charge potential indicat- ed a progressive malfunctioning of energy-producing metabolic cycles. A possible contribution to such a se- vere change in energy state might be related to depletion of NAD and NADP, particularly noticeable after the longest incomplete brain ischemia times, that should have provoked a consequent lessening of oxido-reductive reactions. Bilateral carotid clamping causes a significant reduction in brain oxygen and substrate supply that re- sults in inhibition of energy metabolism and triggering of oxygen-radical-induced lipid peroxidation. &kwd:Key words Cerebral ischemia · Peroxidative damages · Malondialdehyde · Oxypurines · Nucleosides&bdy: Introduction Cerebral ischemia, defined as a reduction in cerebral blood flow to levels that are insufficient to maintain nor- mal brain function or metabolism, is one of the most im- portant pathological conditions encountered in several cerebral disorders. In these circumstances, the estimation of tissue damage related to brain ischemia is of great im- portance for the understanding of the molecular mecha- nisms at the basis of the injury itself. One of the early biochemical events subsequent to central nervous system trauma or ischemia, identified during the last decade, is oxygen radical generation and subsequent lipid peroxidation (Ginsberg et al. 1988; Hall and Braughler 1989; Brown and Hall 1992). During isch- emia, mitochondrial oxidative phosphorylation ceases and cellular levels of ATP drop, while those of ADP and AMP rise significantly. Therefore, AMP is metabolized via the purine salvage pathway to adenosine, inosine and hypoxanthine. Normally, hypoxanthine is transformed by xanthine dehydrogenase (XDH) to xanthine and, ulti- mately, to uric acid. With the onset of ischemia, however, several reports have shown that there is a calcium-depen- R. Vagnozzi ( ✉ ) · B. Fraioli · S. Signoretti Chair of Neurosurgery, Department of “Sanità Pubblica”, University of Rome “Tor Vergata”, Via Tor Vergata 135, I-00133 Rome, Italy; Tel.: +39-6-72596360, Fax: +39-6-59044371 B. Tavazzi · D. Di Pierro Department of Experimental Medicine and Biochemical Sciences, University of Rome “Tor Vergata”, Via Tor Vergata 135, I-00133 Rome, Italy B. Giardina Institute of Chemistry and Clinical Chemistry, and “Centro C.N.R. per lo Studio della Chimica dei Recettori”, Catholic University of Rome “Sacro Cuore”, Largo F. Vito 1, I-00135 Rome, Italy M. Galvano · S. Distefano · G. Lazzarino Institute of Biochemical and Pharmacological Sciences, University of Catania, Viale A. Doria 6, I-90125 Catania, Italy&/fn-block: Exp Brain Res (1997) 117:411–418 © Springer-Verlag 1997 RESEARCH ARTICLE &roles:R. Vagnozzi · B. Tavazzi · D. Di Pierro · B. Giardina B. Fraioli · S. Signoretti · S. Distefano · M. Galvano G. Lazzarino Effects of increasing times of incomplete cerebral ischemia upon the energy state and lipid peroxidation in the rat &misc:Received: 22 July 1996 / Accepted: 17 January 1997