phenobarbital-sodium and Reperfusion-Injury

Excessive glutamate receptor activation is thought to be involved in the retinal ganglion cell (RGC) death after ischemic injury. In this study, we examined the effect of 2-PMPA (2-(phosphonomethyl)pentanedioic acid) on RGC survival in an ischemia-reperfusion model using C57BL/6 mouse eyes. 2-PMPA is a NAALADase (N-acetylated-alpha-linked-acidic dipeptidase) inhibitor, an enzyme responsible for the hydrolysis of the neuropeptide NAAG (N-acetyl-aspartyl-glutamate) to N-acetyl-aspartate and glutamate. 100mg/kg 2-PMPA were given with intraperitoneal injections 30 min before ischemia followed per hour injection for 3h. 2-PMPA increased surviving RGCs as well as retinal thickness after pressure-induced retinal ischemia. In addition, neuroprotection afforded by 2-PMPA was greater than that of N-methyl-D-aspartate receptor blocker. These data indicate that NAALADase inhibition may be useful in retinal disorders in which excessive amino acid transmission is pathogenic.

Topics: Animals; Carboxypeptidases; Glutamate Carboxypeptidase II; Mice; Mice, Inbred C57BL; Neuroprotective Agents; Optic Neuropathy, Ischemic; Organophosphorus Compounds; Pressure; Reperfusion Injury; Retinal Ganglion Cells

Excessive glutamate receptor activation is thought to be involved in the neuronal injury caused by stroke. Based on the hypothesis that N-acetyl-aspartyl-glutamate (NAAG) is a modulatory neurotransmitter or storage form of glutamate, we have pursued a novel strategy of therapeutic intervention, blockade of N-acetylated alpha-linked acidic dipeptidase (NAALADase), the enzyme that hydrolyzes NAAG to liberate glutamate. Using the suture model of transient middle cerebral artery occlusion (MCAO) in rats, the prototype NAALADase inhibitor 2-(phosphonomethyl)pentanedioic acid (2-PMPA) dramatically reduced extracellular glutamate accumulation measured by microdialysis both during a 2-hour occlusion and during reperfusion, consistent with an effect on glutamate supply. During reperfusion, the decrease in glutamate was accompanied by an equimolar, reciprocal rise in extracellular NAAG. NAALADase inhibition may prove to be a well tolerated therapy for cerebral ischemia. In addition, NAALADase inhibitors should prove to be important tools in understanding the physiological role of NAAG in the brain.

Topics: Animals; Carboxypeptidases; Dipeptides; Glutamate Carboxypeptidase II; Glutamic Acid; Infarction, Middle Cerebral Artery; Neuroprotective Agents; Organophosphorus Compounds; Rats; Reperfusion Injury