conotoxin-gv and Brain-Ischemia

Glutamate is the main excitatory neurotransmitter in the central nervous system and it plays a significant role not only in synaptic transmission but also in acute and chronic neuropathologies including stroke. Presently, four receptors for glutamate have been identified and the NMDA receptor family is the most intensively studied. A number of NMDA receptor antagonists have been developed and used for treatment of neurological diseases in patients. However, all of these drugs have been failed in clinical trials either because of intolerable side effects or lack of medical efficacy. Recently, the understanding of molecular structure of NMDA receptors has been advanced and this finding thus provides information for designing subtype-selective antagonists. Using NR2B subunit selective antagonists, ifenprodil and eliprodil, as basic structure models, second and third generation congeners have been developed. Several NR2B-selective compounds showed neuroprotective actions at doses that did not produce measurable side effects in preclinical studies. Some of NR2B subunit selective antagonists have also been tested for the treatment of ischemic brain injury. The present review describes the role of glutamate in ischemic brain injury with an emphasis on the NR2B containing NMDA receptors.

Topics: Animals; Brain; Brain Ischemia; Conotoxins; Drug Design; Excitatory Amino Acid Antagonists; Felbamate; Glutamic Acid; Humans; Neuroprotective Agents; Phenylcarbamates; Piperidines; Propylene Glycols; Protein Conformation; Rats; Receptors, N-Methyl-D-Aspartate

Delayed cell death following ischemic brain injury has been linked to alterations in gene expression. In this study we have evaluated the upregulation of several genes associated with delayed cell death (c-fos, bax, and bcl-2) during the initial 24 h of transient middle cerebral artery occlusion (MCAo) in the rat and the effects of postinjury treatment with the NR2B subunit specific NMDA receptor antagonist CGX-1007 (Conantokin-G, Con-G). C-fos mRNA levels peaked at 1 h postinjury in both cortical and subcortical ischemic brain regions (30-fold increase), remained elevated at 4 h and returned to within normal, preinjury levels 24 h postinjury. The increase in mRNA levels correlated to increased protein expression in the entire ipsilateral hemisphere at 1 h. Regions of necrosis at 4 h were void of C-Fos immunoreactivity with continued upregulation in surrounding regions. At 24 h, loss of C-Fos staining was observed in the injured hemisphere except for sustained increases along the border of the infarct and in the cingulate cortex of vehicle treated rats. CGX-1007 treatment reduced c-fos expression throughout the infarct region by up to 50%. No significant differences were measured in either bcl-2 or bax mRNA expression between treatment groups. However, at 24 h postinjury CGX-1007 treatment was associated with an increase in Bcl-2 immunoreactivity that correlated to a reduction in DNA fragmentation. In conclusion, CGX-1007 effectively attenuated gene expression associated with delayed cell death as related to a neuroprotective relief of cerebral ischemia.

Topics: Animals; Antibodies; bcl-2-Associated X Protein; Brain Ischemia; Cell Death; Conotoxins; DNA Damage; Excitatory Amino Acid Antagonists; Gene Expression; Histocytochemistry; Infarction, Middle Cerebral Artery; Male; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-bcl-2; Proto-Oncogene Proteins c-fos; Rats; Rats, Sprague-Dawley; RNA, Messenger

In focal cerebral ischemia, peri-infarct depolarizations (PIDs) cause an expansion of core-infarcted tissue into adjacent penumbral regions of reversible injury and have been shown to occur through 6 hr after injury. However, infarct maturation proceeds through 24 hr. Therefore, we studied PID occurrence through 72 hr after both transient and permanent middle cerebral artery occlusion (MCAo) via continuous DC recordings in nonanesthetized rats. PIDs occurred an average 13 times before reperfusion at 2 hr and then ceased for an average approximately 8 hr. After this quiescent period, PID activity re-emerged in a secondary phase, which reached peak incidence at 13 hr and consisted of a mean 52 PIDs over 2-24 hr. This phase corresponded to the period of infarct maturation; rates of infarct growth through 24 hr coincided with changes in PID frequency and peaked at 13 hr. In permanent MCAo, PIDs also occurred in a biphasic pattern with a mean of 78 events over 2-24 hr. Parameters of secondary phase PID incidence correlated with infarct volumes in transient and permanent ischemia models. The role of secondary phase PIDs in infarct development was further investigated in transient MCAo by treating rats with a high-affinity NMDA receptor antagonist at 8 hr after injury, which reduced post-treatment PID incidence by 57% and provided 37% neuroprotection. Topographic mapping with multielectrode recordings revealed multiple sources of PID initiation and patterns of propagation. These results suggest that PIDs contribute to the recruitment of penumbral tissue into the infarct core even after the restoration of blood flow and throughout the period of infarct maturation.

Topics: Animals; Brain Ischemia; Cell Death; Conotoxins; Cortical Spreading Depression; Electric Conductivity; Excitatory Amino Acid Antagonists; Infarction, Middle Cerebral Artery; Kinetics; Male; Neuroprotective Agents; Rats; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate

The NMDA antagonist CGX-1007 (Conantokin-G) has previously been shown to possess potent neuroprotective properties when administered intracranially following experimental ischemic brain injury. Using the same model of middle cerebral artery occlusion (MCAo) in rats we now report the neuroprotective effects of CGX-1007 when delivered intrathecally (i.t.). When given 4 h post-occlusion, a reduction in brain infarction was measured along with significant neurological recovery. Furthermore, we describe an i.t. neuroprotective therapeutic window lasting > or = 8 h from the start of the injury. Critically, this is the first comprehensive report of a neuroprotective agent that can be administered i.t. to ameliorate experimental brain injury and potentially provide an excellent therapeutic window as a neuroprotection treatment.

Topics: Animals; Body Weight; Brain Edema; Brain Ischemia; Cerebral Cortex; Conotoxins; Corpus Striatum; Disease Models, Animal; Excitatory Amino Acid Antagonists; Fever; Infarction, Middle Cerebral Artery; Injections, Spinal; Male; Neuroprotective Agents; Rats; Rats, Sprague-Dawley; Telencephalon; Treatment Outcome