Nitric Oxide Measured by a Porphyrinic Micro Sensor in Rat Brain after Transient Middle Cerebral Artery Occlusion

Abstract

Summary: We measured, in vivo, the local concentration of nitric oxide (NO) in cerebral tissue, during and after transient middle cerebral artery occlusion in the rat (n = 8). Baseline concentration of NO was <10-8 M; upon initiation of ischemia, NO concentration increased to -10-6 M and then declined. Reperfusion likewise stim ulated an increase in NO concentration to above baseline Nitric oxide (NO) plays a multifaceted and im portant role in the brain. It is a neurotransmitter (Bredt et aI., 1991) and a free radical (Beckman, 1990(Beckman, , 1991, and it has been implicated in the regu lation of cerebral blood flow (Faraci, 1991;Faraci and Heistad, 1992; Kozniewski et aI. , 1992; Iade cola, 1992) and inflammation (Granger et aI., 1990). NO is also an important factor in pathophysiologi cal events in brain. Recent studies have implicated alterations in cerebral NO levels with ischemic cell damage, particularly with glutamate neurotoxicity after cerebral ischemia (Garthwaite, 1991; Dawson et aI., 1991;Snyder and Bredt, 1992; Nowicki et aI. , 1991). Although NO is a subject of great interest in brain research, to our knowledge, direct in vivo measurements of NO in brain after ischemia have not been performed. NO is a reactive molecule, and 355level. Administration of N-nitro-L-arginine methyl ester (n = 4), an inhibitor of nitric oxide synthase, before onset of ischemia, maintained NO at basal levels. Our data in dicate that large increases in NO occur at onset of isch emia, which may affect tissue response to an ischemic insult. Key Words: Nitric oxide-Middle cerebral artery occlusion-Rat.it is therefore difficult to measure in vivo using stan dard chemical techniques. Here we report the first direct measurement of NO in rat brain during and after cerebral ischemia, using a NO sensitive por phyrinic microsensor . MATERIALS AND METHODSEight male Wistar rats (weighing 260--300 g) were anes thetized with 3.5% halothane for induction and 1% halo thane for maintenance, in a 3:1 N20/02 mixture. Four of the animals were administered a nitric oxide synthase in hibitor, L-NAME (N-nitro-L-arginine methyl ester; 30 mg! kg, i. v.), 15 min before induction of middle cerebral ar tery (MCA) occlusion. The femoral artery was cannulated to monitor arterial blood pressure and for sampling of blood gases. The rectal temperature was maintained at 37.0 ± i.O°C. MCA occlusion was induced for 2 h using a method of intraluminal vascular occlusion (Nagasawa and Kogure, 1989; Zea Longa et aI., 1989; Chen et aI., 1992a). Briefly, the right common carotid artery, external carotid artery, and internal carotid artery were isolated via a ven tral midline incision. The distal end of the external carotid artery was ligated with 5-0 silk suture at the branch of the occipital artery, and the origin of the external carotid ar tery was loosely tied with 5-0 silk suture. A microvascular clip was placed across the common carotid artery and internal carotid artery. A 5-cm length of 4-0 nylon mono filament, with its tip rounded by heating near ...

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Nitric Oxide: Considerations for the Treatment of Ischemic Stroke

“…Occlusion of the middle cerebral artery (MCAo) results in an increased production of NO by 20-fold for up to 30 minutes (Malinski et al, 1993;Kader et al, 1993) most likely through increased calcium availability and activation of nNOS (Huang et al, 1994). Thereafter, the brain tissue NO is reduced below detectable levels for up to 7 days (Malinski et al, 1993;Sugimura et al, 1998), indicating a long-lasting NO deficiency in the ischemic brain. If reperfusion occurs, NO concentration may transiently increase by 50% for about 30 minutes (Fassbender et al, 2000;Uetsuka et al, 2002).…”

Mechanisms of Brain Injury in Bacterial Meningitis: Workshop Summary

“…The concentration of nitric oxide synthase is highest in the brain-i.e., at least 20-fold higher than levels in endothelial cells. Nitric oxide concentrations of2-4 J.LM in ischemic brain [43] account for ,..., 10% of oxygen consumption by the CNS during ischemia. These concentrations should be contrasted with nitric oxide concentrations within macrophages, as opposed to 0.4 J.LM in endothelial cells and much less than 0.1 J.LM in most other cell types.…”