Brain mitochondrial redox state, tissue haemodynamic and extracellular ion responses to four-vessel occlusion and spreading depression in the rat

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Abstract
Fibre-optic surface fiuorometer reflectrometry was used to monitor the NADH (nicotine adenine dinucleotide) redox state from rat brain during three- or four-vessel occlusion. To compare the completeness of the electrocauterization of the vertebral arteries and the effectiveness of the anterior cerebral arteries, two light guides were implanted above the cerebral hemispheres. The NADH level was measured and correlated with the changes in the intensity of the reflected light at the excitation wavelength (366 nm) and to the ECoG (electrocorticogram). In the present study, we used ten rats in which unilateral and bilateral carotid occlusion were performed. In a second group of rats we tested the effects of four-vessel occlusion on the metabolic and extracellular K+ and Ca2+ activities as compared with those recorded under spreading depression conditions. These experiments were done by using the multiprobe assembly (MPA) approach. The results could be summarized as follows: (1) in the four-vessel occlusion model, the level of cerebral ischaemia could be estimated quantitatively, in real-time, by monitoring the NADH redox state; (2) unilateral carotid occlusion (after vertebral coagulation) led to a variable level of ipsilateral ischaemia, depending upon the blood flow compensation between the two hemispheres; (3) fibre-optic fluorometry enabled the correlation of NADH redox state with other physiological parameters as well as during after-brain ischaemia; (4) using the MPA in rats exposed to four-vessel occlusion as well as spreading depression, we identified the differences between the two pathological states, although there were some similarities in the ion homeostasis responses.

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