Pregabalin suppresses calcium-mediated proteolysis and improves stroke outcome

Gabapentinoids for the treatment of stroke

ABSTRACT

Gabapentinoid drugs (pregabalin and gabapentin) have been successfully used in the treatment of neuropathic pain and in focal seizure prevention. Recent research has demonstrated their potent activities in modulating neurotransmitter release in neuronal tissue, oxidative stress, and inflammation, which matches the mechanism of action via voltage-gated calcium channels. In this review, we briefly elaborate on the medicinal history and ligand-binding sites of gabapentinoids. We systematically summarize the preclinical and clinical research on gabapentinoids in stroke, including ischemic stroke, intracerebral hemorrhage, subarachnoid hemorrhage, seizures after stroke, cortical spreading depolarization after stroke, pain after stroke, and nerve regeneration after stroke. This review also discusses the potential targets of gabapentinoids in stroke; however, the existing results are still uncertain regarding the effect of gabapentinoids on stroke and related diseases. Further preclinical and clinical trials are needed to test the therapeutic potential of gabapentinoids in stroke. Therefore, gabapentinoids have both opportunities and challenges in the treatment of stroke.

Neuroinflammatory Biomarkers in the Brain, Cerebrospinal Fluid, and Blood After Ischemic Stroke

The most frequent type of stroke, known as ischemic stroke (IS), is a significant global public health issue. The pathological process of IS and post-IS episodes has not yet been fully explored, but neuroinflammation has been identified as one of the key processes. Biomarkers are objective indicators used to assess normal or pathological processes, evaluate responses to treatment, and predict outcomes, and some biomarkers can also be used as therapeutic targets. After IS, various molecules are produced by different cell types, such as microglia, astrocytes, infiltrating leukocytes, endothelial cells, and damaged neurons, that participate in the neuroinflammatory response within the ischemic brain region. These molecules may either promote or inhibit neuroinflammation and may be released into extracellular spaces, including cerebrospinal fluid (CSF) and blood, due to reasons such as BBB damage. These neuroinflammatory molecules should be valued as biomarkers to monitor whether their expression levels in the blood, CSF, and brain correlate with the diagnosis and prognosis of IS patients or whether they have potential as therapeutic targets. In addition, although some molecules do not directly participate in the process of neuroinflammation, they have been reported to have potential diagnostic or therapeutic value against post-IS neuroinflammation, and these molecules will also be listed. In this review, we summarize the neuroinflammatory biomarkers in the brain, CSF, and blood after an IS episode and the potential value of these biomarkers for the diagnosis, treatment, and prognosis of IS patients.

The α2δ-1-NMDA receptor complex and its potential as a therapeutic target for ischemic stroke

N-methyl-_D-aspartate receptors (NMDARs) play a critical role in excitotoxicity caused by ischemic stroke, but NMDAR antagonists have failed to be translated into clinical practice for treating stroke patients. Recent studies suggest that targeting the specific protein-protein interactions that regulate NMDARs may be an effective strategy to reduce excitotoxicity associated with brain ischemia. α2δ-1 (encoded by the Cacna2d1 gene), previously known as a subunit of voltage-gated calcium channels, is a binding protein of gabapentinoids used clinically for treating chronic neuropathic pain and epilepsy. Recent studies indicate that α2δ-1 is an interacting protein of NMDARs and can promote synaptic trafficking and hyperactivity of NMDARs in neuropathic pain conditions. In this review, we highlight the newly identified roles of α2δ-1-mediated NMDAR activity in the gabapentinoid effects and NMDAR excitotoxicity during brain ischemia as well as targeting α2δ-1-bound NMDARs as a potential treatment for ischemic stroke.

Serum calcium channel subunit α2δ-1 concentrations and outcomes in patients with acute spontaneous intracerebral hemorrhage

BACKGROUND

Voltage-gated calcium channel subunit α2δ-1 plays an important role in acute brain injury. We attempted to investigate whether serum α2δ-1 subunit concentrations are correlated with severity and prognosis following intracerebral hemorrhage (ICH).

METHODS

Serum α2δ-1 subunit concentrations were quantified in 103 ICH patients and 103 healthy controls. National Institutes of Health Stroke Scale (NIHSS) score and hematoma volume were estimated for assessing illness severity. Modified Rankin scale score of 3-6 at 90 days after stroke onset was defined as a worse outcome.

RESULTS

Serum α2δ-1 subunit concentrations were markedly higher in patients than in controls (median, 875.1 vs. 209.3 pg/ml). Serum α2δ-1 subunit concentrations of patients were tightly correlated with NIHSS score (r = 0.589) and hematoma volume (r = 0.594). Serum α2δ-1 subunit concentrations ≥ 875.1 pg/ml independently discriminated development of 90-day poor outcome with odds ratio of 5.228 (95% CI, 2.201-12.418) and area under the receiver operating characteristic curve of 0.794 (95% CI, 0.703-0.867). Serum α2δ-1 subunit concentrations > 973.4 pg/ml predicted 90-day poor outcome with 64.0% sensitivity and 90.6% specificity. The prognostic predictive ability of serum α2δ-1 concentrations was equivalent to those of NIHSS score and hematoma volume (both P > 0.05), and serum α2δ-1 concentrations also significantly improved the prognostic predictive capabilities of NIHSS score and hematoma volume (both P < 0.05).

CONCLUSIONS

Serum α2δ-1 subunit concentrations are intimately correlated with illness severity and are independently associated with poor 90-day outcome, substantializing serum α2δ-1 subunit as a potential prognostic biomarker for ICH.

Superior antioxidant and anti-ischemic neuroprotective effects of cerebrolysin in heat stroke following intoxication of engineered metal Ag and Cu nanoparticles: A comparative biochemical and physiological study with other stroke therapies

Military personnel are often exposed to high environmental heat associated with industrial or ambient abundance of nanoparticles (NPs) affecting brain function. We have shown that engineered metal NPs Ag and Cu exacerbate hyperthermia induced brain pathology. Thus, exploration of novel drug therapy is needed for effective neuroprotection in heat stroke intoxicated with NPs. In this investigation neuroprotective effects of cerebrolysin, a balanced composition of several neurotrophic factors and active peptides fragments exhibiting powerful antioxidant and anti-ischemic effects was examined in heat stroke after NPs intoxication. In addition, its efficacy is compared to currently used drugs in post-stroke therapies in clinics. Thus, levertiracetam, pregabalin, topiramat and valproate were compared in standard doses with cerebrolysin in heat stroke intoxicated with Cu or Ag NPs (50-60nm, 50mg/kg, i.p./day for 7 days). Rats were subjected to 4h heat stress (HS) in a biological oxygen demand incubator at 38°C (Relative Humidity 45-47%; Wind velocity 22.4-25.6cm/s) that resulted in profound increase in oxidants Luminol, Lucigenin, Malondialdehyde and Myeloperoxidase, and a marked decrease in antioxidant Glutathione. At this time severe reductions in the cerebral blood flow (CBF) was seen together with increased blood-brain barrier (BBB) breakdown and brain edema formation. These pathophysiological responses were exacerbated in NPs treated heat-stressed animals. Pretreatment with cerebrolysin (2.5mL/kg, i.v.) once daily for 3 days significantly attenuated the oxidative stress, BBB breakdown and brain edema and improved CBF in the heat stressed group. The other drugs were least effective on brain pathology following heat stroke. However, in NPs treated heat stressed animals 5mL/kg conventional cerebrolysin and 2.5mL/kg nanowired cerebrolysin is needed to attenuate oxidative stress, BBB breakdown, brain edema and to improve CBF. Interestingly, the other drugs even in higher doses used are unable to alter brain pathologies in NPs and heat stress. These observations are the first to demonstrate that cerebrolysin is the most superior antioxidant and anti-ischemic drug in NPs exposed heat stroke, not reported earlier.

Calcium Channel Subunit α2δ-1 as a Potential Biomarker Reflecting Illness Severity and Neuroinflammation in Patients with Acute Ischemic Stroke

BACKGROUND

Voltage-gated calcium channels (VGCCs) dysfunction is involved in the development of acute ischemic stroke (AIS). As a subunit of VGCC complexes, we detected the levels of α2δ-1 subunit in serum and cerebrospinal fluid (CSF) specimens from AIS patients.

METHODS

The study included 105 patients with first-ever AIS, who were admitted within 48 hours after stroke onset. The serum and CSF levels of α2δ-1 were measured with ELISA and the severity of AIS patients was evaluated according to the National Institutes of Health Stroke Scale (NIHSS) score. The cerebral infarct volume was calculated through the Pullicino formula based on the cranial CT or MRI scan. C-reactive protein (CRP) and serum amyloid A (SAA) were measured using the latex-enhanced immunoturbidimetric assay.

RESULTS

Compared to the control subjects, the serum α2δ-1 level was significantly increased in AIS patients with large infarct volume and in severe AIS cases with high NIHSS score, which correlated positively with the inflammatory markers CRP and SAA. Furthermore, the concentration of α2δ-1 in CSF was elevated with the infarct volume, which was higher in severe AIS patients.

CONCLUSION

Our study suggests that the increased α2δ-1 levels in serum and CSF specimens may be used as a potential marker for reflecting VGCCs dysfunction, illness severity and neuroinflammation in AIS patients.

The neuroprotective effects of pregabalin after cerebral ischemia by occlusion of the middle cerebral artery in rats

Activation of presynaptic voltage-gated calcium channels and glutamate release serves a central role in neuronal necrosis after cerebral ischemia. Pregabalin binds to the α2-δ subunit of voltage-gated calcium channels and results in reduced glutamate release. The aim of the current study was to evaluate the effect of pregabalin on cerebral outcome following cerebral ischemia using an established rat model. Male Sprague-Dawley rats were randomized to receive oral administration of 5 mg/kg pregabalin for 1 day (PD1 group) or 5 days (PD5 group), or an equal amount of normal saline for 1 day (SD1 group) or 5 days (SD5 group) after 1 day of middle cerebral artery occlusion (MCAO) and reperfusion. Behavioral tests were assessed at postoperative days 1 and 7. Cerebral infarct volume was measured using a brain MRI scan on days 1 and 7 following surgery. Using immunohistochemistry to detect brain-derived neurotrophic factor (BDNF), histologic examinations of perilesional cortex and ipsilateral hippocampus were performed at postoperative day 7. BDNF-positive immunostaining was more abundant in the perilesional cortex of mice of the PD1 group compared with mice of the SD1 group (P=0.001). In the ipsilateral hippocampus, greater BDNF-positive staining was present in the PD5 group compared with the SD5 group (P=0.04). No statistically significant differences were indicated for behavioral tests or cerebral infarct volume between the PD1 and SD1 groups or the PD5 and SD5 groups. In conclusion, treatment with pregabalin beneficially impacts BDNF expression and histologic cerebral outcome in rats after cerebral ischemia.

Focal Cerebral Ischemia and Reperfusion Induce Brain Injury Through α2δ-1-Bound NMDA Receptors

Background and Purpose- Glutamate NMDARs (N-methyl-D-aspartate receptors) play a major role in the initiation of ischemic brain damage. However, NMDAR antagonists have no protective effects in stroke patients, possibly because they impair physiological functions of NMDARs. α2δ-1 (encoded by Cacna2d1) is strongly expressed in many brain regions. We determined the contribution of α2δ-1 to NMDAR hyperactivity and brain injury induced by ischemia and reperfusion. Methods- Mice were subjected to 90 minutes of middle cerebral artery occlusion followed by 24 hours of reperfusion. Neurological deficits, brain infarct volumes, and calpain/caspase-3 activity in brain tissues were measured. NMDAR activity of hippocampal CA1 neurons was measured in an in vitro ischemic model. Results- Middle cerebral artery occlusion increased α2δ-1 protein glycosylation in the cerebral cortex, hippocampus, and striatum. Coimmunoprecipitation showed that ischemia rapidly enhanced the α2δ-1-NMDAR physical interaction in the mouse brain tissue. Inhibiting α2δ-1 with gabapentin, uncoupling the α2δ-1-NMDAR interaction with an α2δ-1 C terminus-interfering peptide, or genetically ablating Cacna2d1 had no effect on basal NMDAR currents but strikingly abolished oxygen-glucose deprivation-induced NMDAR hyperactivity in hippocampal CA1 neurons. Systemic treatment with gabapentin or α2δ-1 C-terminus-interfering peptide or Cacna2d1 genetic knock-out reduced middle cerebral artery occlusion-induced infarct volumes, neurological deficit scores, and calpain/caspase-3 activation in brain tissues. Conclusions- α2δ-1 is essential for brain ischemia-induced neuronal NMDAR hyperactivity, and α2δ-1-bound NMDARs mediate brain damage caused by cerebral ischemia. Targeting α2δ-1-bound NMDARs, without impairing physiological α2δ-1-free NMDARs, may be a promising strategy for treating ischemic stroke.

Pregabalin affords retinal neuroprotection in diabetic rats: Suppression of retinal glutamate, microglia cell expression and apoptotic cell death

Pregabalin is the first drug to receive FDA approval for treating diabetic neuropathic pain. This study investigated the neuroprotective effect of pregabalin in an experimental model of diabetic retinopathy and tested some possible mechanisms underlying the putative neuroprotective effect. Male Wistar rats received streptozotocin (45 mg/kg) to induce type 1 diabetes mellitus. After two weeks, a course of pregabalin (3, 10 and 30 mg/kg) has been launched for five consecutive weeks. Retinal expression of interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) was estimated by real-time PCR and retinal glutamate content was also estimated. Further, retinal caspase-3 immunoblotting and DNA fragmentation assays determined the degree of apoptosis. Pregabalin improved histopathological abnormalities in diabetic retinas and suppressed the diabetes-enhanced retinal expression of IL-1β, TNF-α, CD₁₁b (a surface marker for microglia) while attenuated expression of caspase-3 and DNA fragmentation versus the diabetic group. In addition, diabetic rats treated with pregabalin displayed reductions in retinal glutamate, nitric oxide and malondialdehyde (MDA) and enhanced reduced glutathione (GSH) content versus the diabetic controls. Furthermore, pregabalin enhanced the histopathological picture and reduced fibrosis in the optic nerve of diabetic rats in addition to suppression of the content of the glia fibrillary acidic protein. The findings provide the first evidence demonstrating that pregabalin alleviates retinal neuroinflammation, apoptosis and oxidative stress in an experimental type 1 diabetes mellitus. Therefore, pregabalin might serve as a potential therapy for retinopathy after adequate clinical research.

Amelioration of spinal cord injury in rats by blocking peroxynitrite/calpain activity

Background

Spinal cord injury (SCI) is one of the leading causes of disability and chronic pain. In SCI-induced pathology, homeostasis of the nitric oxide (NO) metabolome is lost. Major NO metabolites such as S-nitrosoglutathione (GSNO) and peroxynitrite are reported to play pivotal roles in regulating the activities of key cysteine proteases, calpains. While peroxynitrite (a metabolite of NO and superoxide) up regulates the activities of calpains leading to neurodegeneration, GSNO (a metabolite of NO and glutathione) down regulates the activities of calpains leading to neuroprotection. In this study, effect of GSNO on locomotor function and pain threshold and their relationship with the levels of peroxynitrite and the activity of calpain in the injured spinal cord were investigated using a 2-week rat model of contusion SCI.

Results

SCI animals were initially treated with GSNO at 2 h after the injury followed by a once daily dose of GSNO for 14 days. Locomotor function was evaluated by “Basso Beattie and Bresnahan (BBB) locomotor rating scale” and pain by mechanical allodynia. Peroxynitrite level, as expression of 3-nitrotyrosine (3-NT), calpain activity, as the degradation products of calpain substrate alpha II spectrin, and nNOS activity, as the expression phospho nNOS, were measured by western blot analysis. Treatment with GSNO improved locomotor function and mitigated pain. The treatment also reduced the levels of peroxynitrite (3-NT) and decreased activity of calpains. Reduced levels of peroxynitrite resulted from the GSNO-mediated inhibition of aberrant activity of neuronal nitric oxide synthase (nNOS).

Conclusions

The data indicates that higher levels of 3-NT and aberrant activities of nNOS and calpains correlated with SCI pathology and functional deficits. Treatment with GSNO improved locomotor function and mitigated mechanical allodynia acutely post-injury. Because GSNO shows potential to ameliorate experimental SCI, we discuss implications for GSNO therapy in clinical SCI research.

Effect of pregabalin administration upon reperfusion in a rat model of hyperglycemic stroke: Mechanistic insights associated with high-mobility group box 1

Hyperglycemia, which reduces the efficacy of treatments and worsens clinical outcomes, is common in stroke. Ability of pregabalin to reduce neuroexcitotoxicity may provide protection against stroke, even under hyperglycemia. We investigated its protective effect against hyperglycemic stroke and its possible molecular mechanisms. Male Wistar rats administered dextrose to cause hyperglycemia, underwent middle cerebral artery occlusion for 1 h and subsequent reperfusion. Rats were treated with an intraperitoneal injection of 30 mg/kg pregabalin or an equal amount of normal saline at the onset of reperfusion (n = 16 per group). At 24 h after reperfusion, neurological deficit, infarct volume, and apoptotic cell count were assessed. Western blot analysis was performed to determine protein expression of high-mobility group box 1 (HMGB1), toll-like receptor-4 (TLR-4), phosphorylated nuclear factor-kappa B (p-NF-κB), interleukin-1beta (IL-1β), tumor necrosis factor-alpha (TNF-α), phosphorylated inducible and endothelial nitric oxide synthase (p-iNOS, p-eNOS), Bcl-2, Bax, Cytochrome C, and caspase-3 in the brain. Pregabalin-treated rats showed significantly improved neurological function (31% decrease in score), reduced infarct size (by 33%), fewer apoptotic cells (by 63%), and lower expression levels of HMGB1, TLR4, p-NF-κB, IL-1β, and TNF- α, compared with control rats. Decreased p-iNOS and increased p-eNOS expressions were also observed. Expression of Bax, Cytochrome C, and cleaved caspase-3/caspase3 was significantly downregulated, while Bcl-2 expression was increased by pregabalin treatment. Pregabalin administration upon reperfusion decreased neuronal death and improved neurological function in hyperglycemic stroke rats. Cogent mechanisms would include attenuation of HMGB1/TLR-4-mediated inflammation and favorable modulation of the NOS.

Method parameters' impact on mortality and variability in mouse stroke experiments: a meta-analysis

Although hundreds of promising substances have been tested in clinical trials, thrombolysis currently remains the only specific pharmacological treatment for ischemic stroke. Poor quality, e.g. low statistical power, in the preclinical studies has been suggested to play an important role in these failures. Therefore, it would be attractive to use animal models optimized to minimize unnecessary mortality and outcome variability, or at least to be able to power studies more exactly by predicting variability and mortality given a certain experimental setup. The possible combinations of methodological parameters are innumerous, and an experimental comparison of them all is therefore not feasible. As an alternative approach, we extracted data from 334 experimental mouse stroke articles and, using a hypothesis-driven meta-analysis, investigated the method parameters’ impact on infarct size variability and mortality. The use of Swiss and C57BL6 mice as well as permanent occlusion of the middle cerebral artery rendered the lowest variability of the infarct size while the emboli methods increased variability. The use of Swiss mice increased mortality. Our study offers guidance for researchers striving to optimize mouse stroke models.

The neuroprotective effects of R-phenibut after focal cerebral ischemia

R-phenibut is a γ-aminobutyric acid (GABA)-B receptor and α₂-δ subunit of the voltage-dependent calcium channel (VDCC) ligand. The aim of the present study was to test the effects of R-phenibut on the motor, sensory and tactile functions and histological outcomes in rats following transient middle cerebral artery occlusion (MCAO). In this study, MCAO was induced by filament insertion (f-MCAO) or endothelin-1 (ET1) microinjection (ET1-MCAO) in male Wistar or CD rats, respectively. R-phenibut was administrated at doses of 10 and 50mg/kg for 14 days in the f-MCAO or 7 days in the ET1-MCAO. The vibrissae-evoked forelimb-placing and limb-placing tests were used to assess sensorimotor, tactile and proprioceptive function. Quantitative reverse transcriptase-PCR was used to detect brain-derived neurotrophic factor (BDNF) and vascular endothelial growth factor (VEGF) gene expression in the damaged brain hemisphere. Both f-MCAO and ET1-MCAO resulted in statistically significant impairment of sensorimotor function and brain infarction. R-phenibut at a dose of 10mg/kg significantly improved histological outcome at day 7 in the ET1-MCAO. R-phenibut treatment at a dose of 50mg/kg significantly alleviated reduction of brain volume in damaged hemisphere in both f-MCAO and ET1-MCAO. In R-phenibut treated animals a trend of recovery of tactile and proprioceptive stimulation in the vibrissae-evoked forelimb-placing test was observed. After R-phenibut treatment at a dose of 50mg/kg statistically significant increase of BDNF and VEGF gene expression was found in damaged brain hemisphere. Taken together, obtained results provide evidence for the neuroprotective activity of R-phenibut in experimental models of stroke. These effects might be related to the modulatory effects of the drug on the GABA-B receptor and α₂-δ subunit of VDCC.

Targeting the nNOS/peroxynitrite/calpain system to confer neuroprotection and aid functional recovery in a mouse model of TBI

Traumatic brain injury (TBI) derails nitric oxide (NO)-based anti-inflammatory and anti-excitotoxicity mechanisms. NO is consumed by superoxide to form peroxynitrite, leading to decreased NO bioavailability for S-nitrosoglutathione (GSNO) synthesis and regulation of neuroprotective pathways. Neuronal peroxynitrite is implicated in neuronal loss and functional deficits following TBI. Using a contusion mouse model of TBI, we investigated mechanisms for the opposed roles of GSNO versus peroxynitrite for neuroprotection and functional recovery. TBI was induced by controlled cortical impact (CCI) in adult male mice. GSNO treatment at 2h after CCI decreased the expression levels of phospho neuronal nitric oxide synthase (pnNOS), alpha II spectrin degraded products, and 3-NT, while also decreasing the activities of nNOS and calpains. Treatment of TBI with FeTPPS, a peroxynitrite scavenger, had effects similar to GSNO treatment. GSNO treatment of TBI also reduced neuronal degeneration and improved neurobehavioral function in a two-week TBI study. In a cell free system, SIN-1 (a peroxynitrite donor and 3-nitrotyrosinating agent) increased whereas GSNO (an S-nitrosylating agent) decreased calpain activity, and these activities were reversed by, respectively, FeTPPS and mercuric chloride, a cysteine-NO bond cleaving agent. These data indicate that peroxynitrite-mediated activation and GSNO-mediated inhibition of the deleterious nNOS/calpain system play critical roles in the pathobiology of neuronal protection and functional recovery in TBI disease. Given GSNO׳s safety record in other diseases, its neuroprotective efficacy and promotion of functional recovery in this TBI study make low-dose GSNO a potential candidate for preclinical evaluation.

Pregabalin attenuates excitotoxicity in diabetes

Diabetes can exacerbate seizures and worsen seizure-related brain damage. In the present study, we aimed to determine whether the standard antiepileptic drug pregabalin (PGB) protects against pilocarpine-induced seizures and excitotoxicity in diabetes. Adult male Sprague-Dawley rats were divided into either a streptozotocin (STZ)-induced diabetes group or a normal saline (NS) group. Both groups were further divided into subgroups that were treated intravenously with either PGB (15 mg/kg) or a vehicle; all groups were treated with subcutaneous pilocarpine (60 mg/kg) to induce seizures. To evaluate spontaneous recurrent seizures (SRS), PGB-pretreated rats were fed rat chow containing oral PGB (450 mg) for 28 consecutive days; vehicle-pretreated rats were fed regular chow. SRS frequency was monitored for 2 weeks from post-status epilepticus day 15. We evaluated both acute neuronal loss and chronic mossy fiber sprouting in the CA3 area. In addition, we performed patch clamp recordings to study evoked excitatory postsynaptic currents (eEPSCs) in hippocampal CA1 neurons for both vehicle-treated rats with SRS. Finally, we used an RNA interference knockdown method for Kir6.2 in a hippocampal cell line to evaluate PGB's effects in the presence of high-dose ATP. We found that compared to vehicle-treated rats, PGB-treated rats showed less severe acute seizure activity, reduced acute neuronal loss, and chronic mossy fiber sprouting. In the vehicle-treated STZ rats, eEPSC amplitude was significantly lower after PGB administration, but glibenclamide reversed this effect. The RNA interference study confirmed that PGB could counteract the ATP-sensitive potassium channel (K_ATP)-closing effect of high-dose ATP. By opening K_ATP, PGB protects against neuronal excitotoxicity, and is therefore a potential antiepileptogenic in diabetes. These findings might help develop a clinical algorithm for treating patients with epilepsy and comorbid metabolic disorders.

Energy restriction negates NMDA receptor antagonist efficacy in ischemic stroke

Preclinical evaluation of drugs for neurological disorders is usually performed on overfed rodents, without consideration of how metabolic state might affect drug efficacy. Using a widely employed mouse model of focal ischemic stroke, we found that that the NMDA receptor antagonist dizocilpine (MK-801) reduces brain damage and improves functional outcome in mice on the usual ad libitum diet, but exhibits little or no therapeutic efficacy in mice maintained on an energy-restricted diet. Thus, NMDA receptor activation plays a central role in the mechanism by which a high dietary energy intake exacerbates ischemic brain injury. These findings suggest that inclusion of subjects with a wide range of energy intakes in clinical trials for stroke may mask a drug benefit in the overfed/obese subpopulation of subjects.