6-cyano-7-nitroquinoxaline-2-3-dione and Brain-Edema

Decreased cerebral blood flow, hence decreased oxygen and glucose, leads to ischemic brain injury via complex pathophysiological events, including excitotoxicity, mitochondrial dysfunction, increased intracellular Ca2+, and reactive oxygen species (ROS) generation. Each of these could also contribute to cerebral edema, which is the primary cause of patient mortality after stroke. In vitro brain slices are widely used to study ischemia. Here we introduce a slice model to investigate ischemia-induced edema. Significant water gain was induced in coronal slices of rat brain by 5 min of oxygen and glucose deprivation (OGD) at 35 degrees C, with progressive edema formation after return to normoxic, normoglycemic medium. Edema increased with increasing injury severity, determined by OGD duration (5-30 min). Underlying factors were assessed using glutamate-receptor antagonists (AP5/CNQX), blockade of mitochondrial permeability transition [cyclosporin A (CsA) versus FK506], inhibition of Na+/Ca2+ exchange (KB-R7943), and ROS scavengers (ascorbate, Trolox, dimethylthiourea, Tempol). All agents except KB-R7943 and FK506 significantly attenuated edema when applied after OGD; KB-R7943 was effective when applied before OGD. Significantly, complete prevention of ischemia-induced edema was achieved with a cocktail of AP5/CNQX, CsA and Tempo applied after OGD, which demonstrates the involvement of multiple, additive mechanisms. The efficacy of this cocktail further shows the potential value of combination therapies for the treatment of cerebral ischemia.

Topics: 2-Amino-5-phosphonovalerate; 6-Cyano-7-nitroquinoxaline-2,3-dione; Animals; Antioxidants; Brain Edema; Cell Hypoxia; Cyclic N-Oxides; Cyclosporine; Drug Therapy, Combination; Excitatory Amino Acid Antagonists; Glucose; Glutamic Acid; Hypoxia-Ischemia, Brain; In Vitro Techniques; Male; Mitochondria; Neuroprotective Agents; Rats; Rats, Long-Evans; Reactive Oxygen Species; Receptors, Glutamate; Sodium-Calcium Exchanger; Spin Labels; Water

Glutamate receptor-mediated changes in light transmittance were imaged in the dentate gyri of the epileptic hippocampi, taken from patients with temporal lobe epilepsy and the rat pilocarpine model, to investigate epilepsy-associated alterations in activity-induced cell swelling. A static pattern of light transmittance corresponded to the layered structure of dentate gyrus and reflected epilepsy-associated alterations. Hypoosmotic stress produced more than 35% of dynamic changes in the increase of light transmittance as a reflection of osmotic swelling in the epileptic dentate gyri. This degree of increase was not different from the increase observed in control dentate gyri, suggesting that the capability of osmotically regulating cell volume was preserved in the epileptic dentate gyri. In contrast, alpha-amino-3-hydroxy-5-methyl-4-isoxazole proprionic acid (AMPA) induced activity-dependent swelling and an increase in light transmittance by 60.5% in the control dentate gyri, whereas the degree of increase in the epileptic dentate gyri remained 17.9% in response to AMPA. Selective attenuation of light transmittance in response to AMPA in the epileptic but not control dentate gyri suggested a possible alteration in the swelling properties of the epileptic dentate gyri that are linked to the AMPA receptor activation. Surviving cells in the epileptic hippocampus may have a mechanism of downregulating neuronal activity-dependent swelling to maintain optimal cell volume during repeated network hyperexcitation in epilepsy.

Topics: 6-Cyano-7-nitroquinoxaline-2,3-dione; Adult; alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; Animals; Brain Edema; Dentate Gyrus; Epilepsy, Temporal Lobe; Excitatory Amino Acid Agonists; Excitatory Amino Acid Antagonists; Glutamic Acid; Humans; Light; Male; Membrane Potentials; Neurons; Optics and Photonics; Organ Culture Techniques; Osmotic Pressure; Rats; Rats, Sprague-Dawley; Receptors, AMPA; Tetrodotoxin

The hexachlorophene-induced cytotoxic brain oedema is an experimental model of brain damage, suitable for testing cerebroprotective substances (Andreas 1993). In order to examine whether glutamate receptors are involved in mediating functional disorders due to neurotoxic brain damage, we have studied the protective effects of several competitive and non-competitive antagonists using adult male Wistar rats in a simple "ladder-test" for assessing coordinative motor behaviour. Hexachlorophene-induced brain damage was verified by histological examination of the cerebellum with vacuolation of white matter, astrocyte hypertrophy and astrocyte proliferation taken as signs of neurotoxic injury. The non-competitive N-methyl-D-aspartate (NMDA) antagonist dizocilpine maleate (MK-801) decreased the motor disturbance on the first and second day of the "ladder-test" when applied in the doses 0.1 mg/kg and 0.2 mg/kg intraperitoneally for 3 weeks during the hexachlorophene treatment. Acute MK-801 administration (0.1 mg/kg intraperitoneally) after 3 weeks hexachlorophene exposure improved the coordinative motor response only on the first day. When testing the competitive NMDA receptor antagonist 2-amino-5-phosphonopentanoic acid (AP-5) in the dose 1.0 mg/kg intraperitoneally the motor disturbance was lowered significantly earlier than in spontaneous remission. Similar effects were observed with 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) in the dose of 0.8 mg/kg intraperitoneally, an antagonist interacting both with the strychnine-insensitive binding site for glycine within the NMDA receptor complex and with the kainate(+/-)-alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptor complex. Concurrent MK-801 administration decreased the vacuolation of white matter. The results suggest that NMDA receptors and non-NMDA receptors are involved in development of functional disorders induced by hexachlorophene.

Topics: 2-Amino-5-phosphonovalerate; 6-Cyano-7-nitroquinoxaline-2,3-dione; Animals; Brain; Brain Edema; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; Hexachlorophene; Male; Rats; Rats, Wistar; Receptors, Glutamate