dizocilpine-maleate and Subarachnoid-Hemorrhage

Spreading depression (SD)-like depolarizations may augment neuronal damage in neurovascular disorders such as stroke and traumatic brain injury. Spreading ischemia (SI), a particularly malignant variant of SD-like depolarization, is characterized by inverse coupling between the spreading depolarization wave and cerebral blood flow. SI has been implicated in particular in the pathophysiology of subarachnoid hemorrhage. Under physiological conditions, SD is blocked by N-methyl-D-aspartate receptor (NMDAR) antagonists. However, because both SD-like depolarizations and SI occur in presence of an increased extracellular K+ concentration ([K+]o), we tested whether this increase in baseline [K+]o would reduce the efficacy of NMDAR antagonists.. Cranial window preparations, laser Doppler flowmetry, and K+-sensitive/reference microelectrodes were used to record SD, SD-like depolarizations, and SI in rats in vivo; microelectrodes and intrinsic optical signal measurements were used to record SD and SD-like depolarizations in human and rat brain slices.. In vivo, the noncompetitive NMDAR antagonist dizocilpine (MK-801) blocked SD propagation under physiological conditions, but did not block SD-like depolarizations or SI under high baseline [K+]o. Similar results were found in human and rat neocortical slices with both MK-801 and the competitive NMDAR antagonist D-2-amino-5-phosphonovaleric acid.. Our data suggest that elevated baseline [K+]o reduces the efficacy of NMDAR antagonists on SD-like depolarizations and SI. In conditions of moderate energy depletion, as in the ischemic penumbra, or after subarachnoid hemorrhage, NMDAR inhibition may not be sufficient to block these depolarizations.

Topics: 2-Amino-5-phosphonovalerate; Animals; Body Temperature; Brain; Brain Injuries; Cortical Spreading Depression; Dizocilpine Maleate; Electrodes; Excitatory Amino Acid Antagonists; Humans; Ions; Ischemia; Laser-Doppler Flowmetry; Male; Neuroprotective Agents; Potassium; Rats; Rats, Wistar; Receptors, N-Methyl-D-Aspartate; Subarachnoid Hemorrhage

Previous studies of neuronal degeneration induced by the neurotoxin, kainic acid, employed silver stain techniques that are non-quantitative or ELISA measurement of the non-neuronal protein, glial fibrillary acidic protein. As previous studies employed biomarkers that were either non-quantitative or non-neuronal, the present study employed a new neuronally localized biomaker of neuronal damage, cleaved microtubule-associated protein (MAP)-tau (C-tau). The time course of kainate neurotoxicity was quantitatively determined in several brain regions in the present study employing a C-tau specific ELISA. Differences in ELISA determined regional brain levels of C-tau were compared with the density of somatodendritic C-tau labeling qualitatively determined in immunohistochemical anatomical mapping studies of kainic acid-treated animals. Immunoblot studies revealed that the C-tau antibodies employed in the present study were highly specific for proteolytic cleaved C-tau. Immunolabeling of 45 kD-50 kD C-tau proteins was observed only in brain samples from kainic acid-treated but not vehicle-treated rats. Time course studies revealed that C-tau levels determined by ELISA were maximal 3 days after kainic acid with C-tau levels increasing 26-fold in hippocampus, 16-fold in cortex and four-fold in both striatum and hypothalamus. These statistical differences in maximal C-tau levels observed in the ELISA studies were similar to differences qualitatively observed in C-tau immunohistochemical studies. C-tau immunohistochemistry revealed extensive damage in hippocampal regions CA1 and 3, moderate damage in several cortical regions and mild damage in striatum and hypothalamus. Similar cleavage of rat MAP-tau to C-tau has been reported after neuronal degeneration induced by neurotoxic doses of methamphetamine and neuronal degeneration resulting from bacterial meningitis. In humans, C-tau proteolysis has been demonstrated to be a reliable biomarker of neuronal damage in traumatic brain injury and stroke where cerebrospinal C-tau levels are correlated with patient clinical outcome. These data suggest that C-tau proteolysis may prove a reliable species independent biomarker of neuronal degeneration regardless of source of injury.

Topics: Animals; Biomarkers; Brain; Brain Chemistry; Cell Death; Cerebrospinal Fluid; Dizocilpine Maleate; Enzyme-Linked Immunosorbent Assay; Excitatory Amino Acid Agonists; Excitatory Amino Acid Antagonists; Humans; Immunoblotting; Immunohistochemistry; Kainic Acid; Male; Microtubule Proteins; Microtubule-Associated Proteins; Neuregulin-1; Neurons; Neurotoxicity Syndromes; Rats; Rats, Sprague-Dawley; Silver Staining; Subarachnoid Hemorrhage; tau Proteins; Time Factors

This report describes the initial clinical assessment of (+)-3-[123I]Iodo-MK-801 and its potential to provide single photon emission tomographic (SPET) images in vivo of NMDA receptor activation during cerebral ischaemia. Multiple SPET images were obtained in the 120 min after the administration of 150 MBq of (+)-3-[123I]Iodo-MK-801 to five patients with cerebral ischaemia (due to cerebral haemorrhages) and to five normal volunteers. In normal subjects, (+)-3-[123I]Iodo-MK-801 has a rapid uptake into the brain. The tracer has a high non-specific retention in the central nervous system due to its lipophilicity, which was made evident by the retention of tracer in the cerebellum and white matter (brain areas with few NMDA receptors). In all patients with cerebral haemorrhages, the initial uptake of (+)-3-[123I]Iodo-MK-801 into the ipsilateral hemisphere was markedly reduced, consistent with a reduced level of cerebral blood flow. In two of five patients, relatively increased tracer retention at later time points (60-120 min after tracer administration) could be seen in cortical areas adjacent to the site of the haemorrhage, consistent with activated NMDA receptors. In three of the patients, no relatively enhanced tracer retention could be identified. Using (+)-3-[123I]Iodo-MK-801, it may be possible to image excessive glutamate (NMDA) receptor activation during an ischaemic episode in living human patients. The utility of (+)-3-[123I]Iodo-MK-801 as a SPET ligand for assessing modest alterations in NMDA receptor activity may ultimately be limited by its lipophilicity and consequent high non-specific binding.

Topics: Aged; Brain; Brain Ischemia; Cerebral Hemorrhage; Dizocilpine Maleate; Gamma Cameras; Humans; Iodine Radioisotopes; Receptors, N-Methyl-D-Aspartate; Subarachnoid Hemorrhage; Tissue Distribution; Tomography, Emission-Computed, Single-Photon

To detect stress responses of the brain to subarachnoid hemorrhage (SAH), we investigated the expression of immediate early genes (IEGs) and hsp70 mRNA by in situ hybridization. Experimental SAH was produced in 49 rats by endovascular penetration. We also monitored the intracranial pressure (ICP) changes. The genes c-fos and c-jun were induced in the cerebral cortex, hippocampus and dentate gyrus in the penetrated side. mRNA coding for hsp70 was induced in the cerebral cortex, hippocampus, thalamus, hypothalamus and caudoputamen in the penetrated side and extended to the contralateral hemisphere. IEGs in the cerebral cortex were completely blocked by MK-801 pretreatment, but hsp70 mRNA was not. This suggests that the expression of IEGs correlates with spreading depression. The IEGs and hsp70 expression may reflect the severity of SAH impact and relate to the mechanisms of symptomatic vasospasm.

Topics: Animals; Brain Chemistry; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; Gene Expression Regulation; HSP70 Heat-Shock Proteins; In Situ Hybridization; Intracranial Pressure; Proto-Oncogene Proteins c-fos; Proto-Oncogene Proteins c-jun; Rats; Rats, Wistar; RNA, Messenger; Subarachnoid Hemorrhage