conotoxin-gv and Disease-Models--Animal

The neuroprotective activity of conantokin-G (con-G), a naturally occurring antagonist of N-methyl-D-aspartate receptors (NMDAR), was neurologically and histologically compared in the core and peri-infarct regions after ischemia/reperfusion brain injury in male Sprague-Dawley rats. The contralateral regions served as robust internal controls. Intrathecal injection of con-G, post-middle carotid artery occlusion (MCAO), caused a dramatic decrease in brain infarct size and swelling at 4 hr, compared to 26 hr, and significant recovery of neurological deficits was observed at 26 hr. Administration of con-G facilitated neuronal recovery in the peri-infarct regions as observed by decreased neurodegeneration and diminished calcium microdeposits at 4 hr and 26 hr. Intact Microtubule Associated Protein (MAP2) staining and neuronal cytoarchitecture was observed in the peri-infarct regions of con-G treated rats at both timepoints. Con-G restored localization of GluN1 and GluN2B subunits in the neuronal soma, but not that of GluN2A, which was perinuclear in the peri-infarct regions at 4 hr and 26 hr. This suggests that molecular targeting of the GluN2B subunit has potential for reducing detrimental consequences of ischemia. Overall, the data demonstrated that stroke-induced NMDAR excitoxicity is ameliorated by con-G-mediated repair of neurological and neuroarchitectural deficits, as well as by reconstituting neuronal localization of GluN1 and GluN2B subunits in the peri-infarct region of the stroked brain.

Topics: Animals; Brain; Brain Infarction; Conotoxins; Disease Models, Animal; Male; Microtubule-Associated Proteins; Neurons; Neuroprotective Agents; Protein Subunits; Protein Transport; Rats; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate; Reperfusion Injury; Time Factors; Treatment Outcome

There are a number of neurologically active ion channel blocking peptides derived from cone snail venom, such as conantokin-G and omega-conotoxin MVIIA. Conantokin-G inhibits NMDA receptors containing the NR2B subunit whereas omega-conotoxin MVIIA blocks N-type Ca(2+) channels. Separately, these peptides induce antinociceptive effects in pre-clinical pain models following intrathecal injection. In the current study, the efficacies of these peptides were determined separately and in combination by intrathecal injection into rats with a spinal nerve ligation, in rats with a spinal cord compression injury and in the formalin test. Separately, both conantokin-G and omega-conotoxin MVIIA dose-dependently attenuated nociceptive responses in all of these models. However, at high antinociceptive doses for both formalin and nerve injury models, omega-conotoxin MVIIA evoked untoward side effects. Using isobolographic analysis, the combination of sub-antinociceptive doses of peptides demonstrated additive antinociception in rats with a nerve ligation and in the formalin test, without apparent adverse side effects. In a model of neuropathic spinal cord injury pain, which is clinically difficult to treat, the combination of conantokin-G and omega-conotoxin MVIIA resulted in robust synergistic antinociception. These data suggest that a combination of these peptides may be analgesic across diverse clinical pains with limited untoward side effects, and particularly potent for reducing spinal cord injury pain.

Topics: Analgesics; Animals; Conotoxins; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Synergism; Hyperalgesia; Male; Motor Activity; Neuralgia; omega-Conotoxins; Pain Measurement; Pain Threshold; Rats; Rats, Sprague-Dawley; Reaction Time; Rotarod Performance Test; Time Factors

The potent NMDA receptor antagonist, Conantokin-G (CGX-1007), a snail peptide, has an 8-h therapeutic window in rat focal cerebral ischemia. We hypothesized that the mechanism of neuroprotection is the inhibition of 'secondary phase' peri-infarct depolarizations (PIDs), recently shown to recur 6--24 h post-reperfusion. Rats were implanted with intrathecal (i.t.) catheters for drug delivery and DC-compatible electrodes for continuous PID monitoring and subjected to transient (2 h) middle cerebral artery occlusion. Four groups were studied. In two groups (C(40)C and C(20)C), continuous infusion of CGX--1007 was administered over 8--24 h post-occlusion at 0.1 microg/h (0.04 nmol/h) following either a 40- or 20-nmol bolus dose at 8 h. Another group (C(40)S) received the 40-nmol bolus followed by saline infusion, and a control group received saline. Intrathecal drug treatment reduced infarct volumes relative to controls by 61%, 31%, and 10% in C(40)C, C(40)S, and C(20)C groups, respectively, but also induced dose-dependent paralysis and elevated mortality. All rats had PID rates similar to the control group prior to treatment, but following treatment secondary phase PIDs were reduced by 47--57% in each drug group compared to controls. Because several animals exhibited PID inhibition but no neuroprotection, there was no significant correlation between these endpoints across groups. However, drug-treated animals that did not exhibit secondary phase PIDs prior to treatment had significantly smaller infarcts and reduced subsequent PID activity than corresponding control rats. Results suggest that post-reperfusion PIDs play a substantial, though still undefined pathogenic role in delayed maturation of cerebral infarction and NMDA receptor-targeted neuroprotection.

Topics: Analysis of Variance; Animals; Body Temperature; Body Weight; Brain Infarction; Conotoxins; Cortical Spreading Depression; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Administration Schedule; Electrodes; Excitatory Amino Acid Antagonists; Infarction, Middle Cerebral Artery; Ischemia; Male; Rats; Rats, Sprague-Dawley; Reperfusion; Time Factors

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