NADH fluorescence in vivo: changes in cerebral oxidative metabolism and perfusion induced by pentobarbital, indomethacin, and salicylate

Mitochondrial function and brain Metabolic Score (BMS) in ischemic Stroke: Evaluation of "neuroprotectants" safety and efficacy

The initial and significant event developed in ischemic stroke is the sudden decrease in blood flow and oxygen supply to brain tissue, leading to dysfunction of the mitochondria. Many attempts were and are being made to develop new drugs and treatments that will save the ischemic brain, but the efficacy is not optimal and in many patients, irreversible damage to the brain will persist. We review a unique approach to evaluate mitochondrial function and microcirculatory hemodynamic in real time in vivo. Three out of four monitored physiological parameters are integrated into a new Brain Metabolic Score (BMS) calculated in real time and is correlated to Brain Oxygen Balance. The technology was adapted to various experimental as well as clinical situations for monitoring the brain in real time. The developed protocols could be used in testing the efficacy and safety of new drugs in experimental animals. Few models of brain monitoring during partial or complete ischemia were developed and used in naive animals or under brain activation protocols. It was found that mitochondrial function/dysfunction is the major and dominant parameter affecting the calculated Brain Metabolic Score. Using our monitoring system and protocols will provide direct information regarding the ability of the tested brain to provide enough oxygen consumed by the mitochondria in the "resting" or in the "activated" brain in vivo and in real-time. Preliminary studies, indicated that testing the efficacy and safety of new neuroprotectant drugs provided significant results to the R&D studies of ischemic stroke related to mitochondrial function.

Cerebral metabolic response to low blood flow: possible role of cytochrome oxidase inhibition

The reactions of cerebral metabolism to imposed changes of cerebral blood flow (CBF) are poorly understood. A common explanation of the mismatched CBF and oxygen consumption (CMR(O(2))) during neuronal excitation holds that blood flow rises more than oxygen consumption to compensate for an absent oxygen reserve in brain mitochondria. The claim conversely implies that oxygen consumption must decline when blood flow declines. As the prevailing rate of reaction of oxygen with cytochrome c oxidase is linked to the tension of oxygen, the claim fails to explain how oxygen consumption is maintained during moderate reductions of CBF imposed by hyperventilation (hypocapnia) or cyclooxygenase (COX) inhibition. To resolve this contradiction, we extended the previously published oxygen delivery model with a term allowing for the adjustment of the affinity of cytochrome c oxidase to a prevailing oxygen tension. The extended model predicted constant oxygen consumption at moderately reduced blood flow. We determined the change of affinity of cytochrome c oxidase in the extended model by measuring CBF in seven, and CMR(O(2)) in five, young healthy volunteers before and during COX inhibition with indomethacin. The average CBF declined 35%, while neither regional nor average CMR(O(2)) changed significantly. The adjustment of cytochrome c oxidase affinity to the declining oxygen delivery could be ascribed to a hypothetical factor with several properties in common with nitric oxide.

Effects of indomethacin on cerebral blood flow and oxygen metabolism: a positron emission tomographic investigation in the anaesthetized baboon

The aim of this study was to clarify the controversy about the effects of indomethacin on the coupling of cerebral blood flow (CBF) to cerebral oxygen metabolism (CMRO2). CBF, blood volume (CBV), oxygen extraction fraction (OEF) and CMRO2 were measured by positron emission tomography (PET) in five anaesthetized baboons before and during an i.v. administration of indomethacin (bolus 20 mg/kg followed by perfusion 10 mg/kg.h). Administration of indomethacin resulted in a marked and homogenous decrease of CBF in every region analysed (-28% to -40%) and a moderate reduction in CBV (-8% to -16%). In contrast, CMRO2 displayed a small increase in thalamus and pons (+10% and +13%, respectively). OEF increased greatly in all structures studied (+59% to +96%). These findings show that the potent cerebrovascular effects of indomethacin are not related to a decrease in CMRO2 as measured through the use of PET.

Microvascular changes during the early phase of experimental bacterial meningitis

We investigated the temporal profile of the changes in regional CBF (rCBF) and intracranial pressure (ICP) during the early phase of pneumococcal meningitis in the rat. rCBF, as measured by laser-Doppler flowmetry, and ICP were continuously monitored during 6 h post infection (p.i.). Brain edema formation was assessed by brain water content determinations. Meningitis was induced by intracisternal injection of 75 microliters of 10(7) colony-forming units/ml pneumococci (n = 7). In control animals (n = 6), saline was injected. There was no change in the rCBF or ICP of controls throughout the experiment. However, there was a dramatic increase in rCBF and ICP associated with brain edema formation in untreated meningitis animals. rCBF increased to 135.3 +/- 33.8% (mean +/- SD) in the untreated animals at 1 h p.i. and reached 211.1 +/- 40.5% at 6 h p.i. (p less than 0.05 compared with controls). ICP increased from 2.9 +/- 1.4 to 10.4 +/- 4.7 mm Hg at 6 h p.i. (p less than 0.05 compared with controls). Brain water content was significantly elevated (79.69 +/- 0.24 compared with 78.94 +/- 0.16% in the control group, p less than 0.05). We investigated the effect of dexamethasone (3 mg/kg i.p.), which was given prior to the induction of meningitis (n = 3) or at 2 h after pneumococcal injection (n = 5), indomethacin (10 mg/kg i.v., n = 5), and superoxide dismutase (SOD; 132,000 U/kg i.v. per 6 h, n = 6).(ABSTRACT TRUNCATED AT 250 WORDS)

Temporal evolution of regional energy metabolism following focal cerebral ischemia in the rat

Focal cerebral ischemia in the rat was induced by occlusion of the left middle cerebral artery. The temporal evolution of regional energy metabolism was studied over the 14 days consequent to the induction of ischemia in the frontal, cingulate, parietal, and occipital cortices as well as in the striatum. Regional concentrations of adenosine triphosphate (ATP), phosphocreatine, and lactate and, in addition, glucose and the cerebral/plasma glucose ratio (C/P) were measured in the hemispheres both ipsilateral and contralateral to the occlusion. Two hours after middle cerebral artery occlusion, the biochemical changes were severe in the striatum and moderate in cortical regions. Later on (at 24 and 48 h), an overall aggravated metabolic status was noted while lactate declined and glucose markedly increased. These latter biochemical changes likely indicate a marked inhibition of the rate of glucose utilization. At 48 h, the energy reserves (ATP, phosphocreatine) of parietal cortex no longer equaled those of other cortical regions, but abruptly fell to the levels found in the striatum without any increase in lactate level. Finally, at 7 and 14 days, the levels of the various metabolites in most cortical regions returned toward control values, although signs of a depressed glucose metabolism remained. However, in both striatum and parietal cortex, ATP and phosphocreatine concentrations, although higher than those observed at 48 h, remained significantly decreased. Our present biochemical study permits the classification of these selected brain regions into three categories. First there are those that are outside the area of infarction: the frontal, cingulate, and occipital cortices. These regions show little temporal evolution of brain energy metabolism but, notwithstanding, they are regions in which glucose use would appear to be greatly depressed. Second is a region considered to be the focus of infarction: the striatum. The caudate-putamen is a region with early and profound metabolic disturbances with no final restitution. Last is the region of metabolic penumbra--the parietal cortex, in which there is a time-related exacerbation of the consequences of middle cerebral occlusion in the rat.