AMPA Receptor-mediated Excitotoxicity Research Articles

C9ORF72 repeat expansion causes vulnerability of motor neurons to Ca2+-permeable AMPA receptor-mediated excitotoxicity

Mutations in C9ORF72 are the most common cause of familial amyotrophic lateral sclerosis (ALS). Here, through a combination of RNA-Seq and electrophysiological studies on induced pluripotent stem cell (iPSC)-derived motor neurons (MNs), we show that increased expression of GluA1 AMPA receptor (AMPAR) subunit occurs in MNs with C9ORF72 mutations that leads to increased Ca2+-permeable AMPAR expression and results in enhanced selective MN vulnerability to excitotoxicity. These deficits are not found in iPSC-derived cortical neurons and are abolished by CRISPR/Cas9-mediated correction of the C9ORF72 repeat expansion in MNs. We also demonstrate that MN-specific dysregulation of AMPAR expression is also present in C9ORF72 patient post-mortem material. We therefore present multiple lines of evidence for the specific upregulation of GluA1 subunits in human mutant C9ORF72 MNs that could lead to a potential pathogenic excitotoxic mechanism in ALS.

Calpain-Dependent Degradation of Nucleoporins Contributes to Motor Neuron Death in a Mouse Model of Chronic Excitotoxicity.

Glutamate-mediated excitotoxicity induces neuronal death by altering various intracellular signaling pathways and is implicated as a common pathogenic pathway in many neurodegenerative diseases. In the case of motor neuron disease, there is significant evidence to suggest that the overactivation of AMPA receptors due to deficiencies in the expression and function of glial glutamate transporters GLT1 and GLAST plays an important role in the mechanisms of neuronal death. However, a causal role for glial glutamate transporter dysfunction in motor neuron death remains unknown. Here, we developed a new animal model of excitotoxicity by conditionally deleting astroglial glutamate transporters GLT1 and GLAST in the spinal cords of mice (GLAST+/-/GLT1-cKO). GLAST+/-/GLT1-cKO mice (both sexes) exhibited nuclear irregularity and calpain-mediated degradation of nuclear pore complexes (NPCs), which are responsible for nucleocytoplasmic transport. These abnormalities were associated with progressive motor neuron loss, severe paralysis, and shortened lifespan. The nuclear export inhibitor KPT-350 slowed but did not prevent motor neuron death, whereas long-term treatment of the AMPA receptor antagonist perampanel and the calpain inhibitor SNJ-1945 had more persistent beneficial effects. Thus, NPC degradation contributes to AMPA receptor-mediated excitotoxic motor neuronal death, and preventing NPC degradation has robust protective effects. Normalization of NPC function could be a novel therapeutic strategy for neurodegenerative disorders in which AMPA receptor-mediated excitotoxicity is a contributory factor.SIGNIFICANCE STATEMENT Despite glial glutamate transporter dysfunction leading to excitotoxicity has been documented in many neurological diseases, it remains unclear whether its dysfunction is a primary cause or secondary outcome of neuronal death at disease state. Here we show the combined loss of glial glutamate transporters GLT1 and GLAST in spinal cord caused motor neuronal death and hindlimb paralysis. Further, our novel mutant exhibits the nuclear irregularities and calpain-mediated progressive nuclear pore complex degradation. Our study reveals that glial glutamate transporter dysfunction is sufficient to cause motor neuronal death in vivo.

Excitation BolsTORs Motor Neurons in ALS Mice

It is unclear why motor neurons selectively degenerate in amyotrophic lateral sclerosis (ALS). Saxena etal. (2013) demonstrate that excitation of motor neurons can prevent their demise in a mouse model of inherited ALS by a mechanism involving the mTOR pathway.

Intracellular Ca2+ release through ryanodine receptors contributes to AMPA receptor-mediated mitochondrial dysfunction and ER stress in oligodendrocytes

Overactivation of ionotropic glutamate receptors in oligodendrocytes induces cytosolic Ca2+ overload and excitotoxic death, a process that contributes to demyelination and multiple sclerosis. Excitotoxic insults cause well-characterized mitochondrial alterations and endoplasmic reticulum (ER) dysfunction, which is not fully understood. In this study, we analyzed the contribution of ER-Ca2+ release through ryanodine receptors (RyRs) and inositol triphosphate receptors (IP3Rs) to excitotoxicity in oligodendrocytes in vitro. First, we observed that oligodendrocytes express all previously characterized RyRs and IP3Rs. Blockade of Ca2+-induced Ca2+ release by TMB-8 following α-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate (AMPA) receptor-mediated insults attenuated both oligodendrocyte death and cytosolic Ca2+ overload. In turn, RyR inhibition by ryanodine reduced as well the Ca2+ overload whereas IP3R inhibition was ineffective. Furthermore, AMPA-triggered mitochondrial membrane depolarization, oxidative stress and activation of caspase-3, which in all instances was diminished by RyR inhibition. In addition, we observed that AMPA induced an ER stress response as revealed by α subunit of the eukaryotic initiation factor 2α phosphorylation, overexpression of GRP chaperones and RyR-dependent cleavage of caspase-12. Finally, attenuating ER stress with salubrinal protected oligodendrocytes from AMPA excitotoxicity. Together, these results show that Ca2+ release through RyRs contributes to cytosolic Ca2+ overload, mitochondrial dysfunction, ER stress and cell death following AMPA receptor-mediated excitotoxicity in oligodendrocytes.

VEGF protects motor neurons against excitotoxicity by upregulation of GluR2

Influx of Ca(2+) ions through the α-amino-3-hydroxy-5-methylisoxazole propionic acid (AMPA) receptors is toxic to neurons and contributes to motor neuron degeneration observed in amyotrophic lateral sclerosis (ALS). The Ca(2+) permeability of the AMPA receptor depends on its subunit composition. If the GluR2 subunit is present in the receptor complex, the AMPA receptor is impermeable to Ca(2+). In this study, we identified vascular endothelial growth factor-A (VEGF) as a GluR2 inducing molecule. Cultured motor neurons pretreated with VEGF displayed higher GluR2 levels. This resulted in AMPA receptor currents with a low relative Ca(2+) permeability and in motor neurons that were less vulnerable to AMPA receptor-mediated excitotoxicity. This effect of VEGF was mediated through the VEGFR2 present on the motor neurons and was due to stimulation of GluR2 transcription. Intracerebroventricular treatment with VEGF similarly induced GluR2 expression in the ventral spinal cord of rats and this mechanism contributes to the protective effect of VEGF on motor neurons.

Morphological features and responses to AMPA receptor-mediated excitotoxicity of mouse motor neurons: comparison in purified, mixed anterior horn or motor neuron/glia cocultures

Primary motor neuron cultures are widely used as in vitro model to study the early mechanisms involved in the aetiology of amyotrophic lateral sclerosis. In this study, we directly compared the morphological features and the responses to AMPA receptor (AMPAR) activation of mouse spinal cord motor neurons under different culture conditions (OptiPrep-purified, mixed anterior horn or motor neuron/glia cocultures). Motor neurons cocultured with a confluent glial layer had significant improvements in axonal length and in somata perimeter and area, compared both to mixed anterior horn cultures and to purified cultures, suggesting that the presence of more “mature” glial cells was determinant to obtain healthier motor neurons. By immuno-cytochemical assays we found that both in mixed anterior horn cultures and in cocultures, lower AMPA (0.3 μM) or kainate (5 μM) concentrations, but not the higher (1 or 15 μM, respectively), induced classical apoptotic events such as the nuclear fragmentation, the membrane externalization of phosphatidylserine residues and the activation of caspases-9 and -3. The morphological features and the different degenerative pathways induced by AMPAR agonist concentrations suggest that the experimental conditions used for in vitro studies are key factors that should be deeply considered to obtain more valid and reproducible results.

Attenuation of AMPA receptor activity improves motor skills in a mouse model of juvenile Batten disease

Juvenile Batten disease, caused by mutations in the CLN3 gene, is a fatal, incurable neurodegenerative disorder in children. The Cln3-loss-of-function (Cln3Δex1–6) mouse model of the disease exhibits many characteristic pathological features of the human disorder including a deficit in motor skills. Our recent findings [Kovács, A.D., Weimer, J.M., Pearce, D.A., 2006. Selectively increased sensitivity of cerebellar granule cells to AMPA receptor-mediated excitotoxicity in a mouse model of Batten disease. Neurobiol. Dis. 22, 575–585] suggested that the neurological deficit in the Cln3Δex1–6 mouse model of the disease might result from an abnormally increased AMPA receptor activity in the cerebellum. Therefore, we tested if administration of low doses of an AMPA receptor antagonist, that attenuate AMPA receptor function but avoid a toxic, complete blockade of the receptor, have beneficial effects in Cln3Δex1–6 mice. Here we show that attenuation of AMPA receptor activity by a single intraperitoneal injection of the non-competitive AMPA antagonist, EGIS-8332 (1 mg/kg), significantly improves the motor skills of Cln3Δex1–6 mice. Our results provide a new, promising therapeutic approach for juvenile Batten disease.

Astrocytes regulate GluR2 expression in motor neurons and their vulnerability to excitotoxicity

Influx of Ca(2+) ions through alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptors contributes to neuronal damage in stroke, epilepsy, and neurodegenerative disorders such as ALS. The Ca(2+) permeability of AMPA receptors is largely determined by the glutamate receptor 2 (GluR2) subunit, receptors lacking GluR2 being permeable to Ca(2+) ions. We identified a difference in GluR2 expression in motor neurons from two rat strains, resulting in a difference in vulnerability to AMPA receptor-mediated excitotoxicity both in vitro and in vivo. Astrocytes from the ventral spinal cord were found to mediate this difference in GluR2 expression in motor neurons. The presence of ALS-causing mutant superoxide dismutase 1 in astrocytes abolished their GluR2-regulating capacity and thus affected motor neuron vulnerability to AMPA receptor-mediated excitotoxicity. These results reveal a mechanism through which astrocytes influence neuronal functioning in health and disease.

Role of mitochondria in kainate-induced fast Ca 2+ transients in cultured spinal motor neurons

Motor neuron death in amyotrophic lateral sclerosis (ALS) has been linked to selective vulnerability towards AMPA receptor-mediated excitotoxicity. We investigated intracellular mechanisms leading to impairment of motor neuron Ca 2+ homeostasis with near physiological AMPA receptor activation. Using fast solution exchange on patch-clamped cultured neurons, kainate (KA) was applied for 2 s. This induced a transient increase in the cytosolic Ca 2+ concentration ([Ca 2+] c) for seconds. Inhibition of the mitochondrial uniporter by RU-360 abolished the decay of the Ca 2+ transient and caused immediate [Ca 2+] c overload. Repetitive short KA stimulation caused a slowing of the decay of the Ca 2+ transient and a gradual increase in peak and baseline [Ca 2+] c in motor neurons, but not in other neurons, indicating saturation of the mitochondrial buffer. Furthermore, mitochondrial density was lower in motor neurons and, in a network of neurons with physiological synaptic AMPA receptor input, RU-360 acutely induced an increase in Ca 2+ transients. We conclude that motor neurons have an insufficient mitochondrial capacity to buffer large Ca 2+ elevations which is partly due to a reduced mitochondrial density per volume compared to non-motor neurons. This may exert deleterious effects in motor neuron disease where mitochondrial function is thought to be compromised.

Selectively increased sensitivity of cerebellar granule cells to AMPA receptor-mediated excitotoxicity in a mouse model of Batten disease

Batten disease, a lysosomal storage disorder, is caused by mutations in the CLN3 gene. The Cln3-knockout (Cln3-/-) mouse model of the disease exhibits many characteristic pathological features of the human disorder. Here, we show that Cln3-/- mice, similarly to Batten disease patients, have a deficit in cerebellar motor coordination. To explore the possible cellular cause of this functional impairment, we compared the vulnerability of wild type (WT) and Cln3-/- cerebellar granule cell cultures to different toxic insults. We have found that cultured Cln3-/- cerebellar granule cells are selectively more vulnerable to AMPA-type glutamate receptor-mediated toxicity than their WT counterparts. This selective sensitivity was also observed in organotypic cerebellar slice cultures. Our results suggest that lack of the CLN3 protein has a significant influence on the function of AMPA receptors in cerebellar granule neurons, and that AMPA receptor dysregulation may be a major contributor to the cerebellar dysfunction in Batten disease.

GluR2 Deficiency Accelerates Motor Neuron Degeneration in a Mouse Model of Amyotrophic Lateral Sclerosis

AMPA receptor-mediated excitotoxicity has been implicated in the selective degeneration of motor neurons in amyotrophic lateral sclerosis (ALS). Motor neurons in vitro are particularly vulnerable to excessive AMPA receptor stimulation and one of the factors underlying this selective vulnerability is the presence of a large proportion of Ca2+ -permeable (i.e. GluR2-lacking) AMPA receptors. However, the precise role of GluR2-lacking AMPA receptors in motor neuron degeneration remains to be defined. We therefore studied the impact of GluR2 deficiency on motor neuron death in vitro and in vivo. Cultured motor neurons from GluR2-deficient embryos displayed an increased Ca2+ influx through AMPA receptors and an increased vulnerability to AMPA receptor-mediated excitotoxicity. We deleted the GluR2 gene in mutant SOD1G93A mice by crossbreeding them with GluR2 knockout mice. GluR2 deficiency clearly accelerated the motor neuron degeneration and shortened the life span of mutant SOD1G93A mice. These findings indicate that GluR2 plays a pivotal role in the vulnerability of motor neurons in vitro and in vivo, and that therapies that limit Ca2+ entry through AMPA receptors might be beneficial in ALS patients.

Expression profile of AMPA receptor subunit mRNA in single adult rat brain and spinal cord neurons in situ

The differential expression of AMPA receptor subunit mRNA was analyzed in the adult rat brain and spinal cord using quantitative RT-PCR with laser capture microdissection. The expression of all four AMPA receptor subunits was demonstrable, with the mRNA expression level for GluR2 being the highest in all the brain areas and neuronal subsets examined. Both the absolute expression level of GluR2 mRNA and its expression relative to the other subunits were the lowest in motoneurons. The unique AMPA receptor expression profile of motoneurons may render them selectively vulnerable to AMPA receptor-mediated excitotoxicity.

P2-009 The positive allosteric modulator of AMPA receptors, S 18986, is neuroprotective in neonatal mouse brain: interaction with neurotrophins

Excitatory neurotransmission at many CNS synapses depends upon AMPA-type glutamate receptors. Derangements in AMPA receptor-mediated synaptic transmission may be a contributing factor in neurological and neurodegenerative diseases and could be a target for therapeutic intervention. Drugs that positively modulate AMPA receptors by reducing AMPA receptor desensitization and/or slowing AMPA receptor deactivation, such as thiazide derivatives (cyclothiazide, diazoxide, IDRA 21) and benzoylpiperidine derivatives (1-BCP, CX516, aniracetam), facilitate AMPA receptor-mediated processes and may have beneficial therapeutic effects. For example, AMPA modulators facilitate long-term potentiation, which may be important for memory storage, and facilitate memory encoding in behavioral experiments. Thus, AMPA modulators might ameliorate memory deficits that occur in dementia, such as Alzheimer's disease. However, AMPA receptor-mediated excitotoxicity may occur with excessive AMPA receptor activation such as in seizures or ischemia, and positive AMPA modulators would promote neuronal injury under those conditions. Regardless of the ultimate clinical utility of positive AMPA modulators, their discovery and study have already provided significant insight into the physiology and structural determinants of important AMPA receptor properties. This review attempts to synthesize a variety of studies that have utilized these AMPA modulators to gain insight into fundamental as well as clinically relevant AMPA receptor-mediated processes.

Intracerebral injection of AMPA causes axonal damage in vivo

Brain injury following acute and chronic neurological conditions can involve both neuronal perikaryal and axonal damage, yet considerably less is known about the mechanisms of axonal damage. Oligodendrocytes and myelin are highly vulnerable to AMPA receptor-mediated excitotoxicity. In vitro studies using isolated white matter preparations have shown that AMPA receptor-mediated excitotoxicity results in axonal damage. The effect of AMPA on axons in vivo remains to be determined. We established an in vivo model to determine if axons were vulnerable to AMPA-mediated toxicity, and furthermore, to examine if axonal damage occurred through an AMPA receptor-mediated mechanism. Adult rats received stereotaxic injection of AMPA (2.5 or 25 nmol) or vehicle (PBS) into the external capsule. Axonal damage was detected in the external capsule and cortex in sections immunostained for cytoskeletal components microtubule associated protein-5 (MAP 5), the 200 kDa neurofilament subunit (NF 200) and non-phosphorylated neurofilament-H (SMI 32). Quantification of axonal damage in the external capsule of MAP 5-immunostained sections showed that AMPA caused a significant, dose-dependent increase in axonal damage compared to the vehicle-treated controls. AMPA also induced a dose-dependent increase in myelin and neuronal perikaryal damage. Systemic administration of the AMPA receptor antagonist SPD 502 significantly reduced the amount of AMPA-induced axonal, myelin and neuronal damage. These data suggest that AMPA induces structural damage to the cytoskeleton of axons in vivo, as well as neuronal and myelin damage, and that this occurs through AMPA receptor-mediated mechanisms. AMPA receptor antagonism may have therapeutic potential to salvage both axons and neuronal perikarya in a number of neurological disorders.

Chloride Influx Aggravates Ca2+-Dependent AMPA Receptor-Mediated Motoneuron Death

AMPA receptor-mediated excitotoxicity has been implicated in the pathogenesis of stroke, neurotrauma, epilepsy, and many neurodegenerative diseases such as motoneuron disease. We studied the role of Cl- in AMPA receptor-mediated Ca2+-dependent excitotoxicity in cultured rat spinal motoneurons. Using the gramicidin perforated patch-clamp technique, the intracellular Cl- concentration could be calculated from the reversal potential of the GABA-induced current. The membrane depolarization caused by AMPA receptor stimulation resulted in Cl- influx through 5-nitro-2(3-phenylpropyl-amino) benzoic acid- and niflumic acid-sensitive Cl- channels. Cl- influx during AMPA receptor stimulation aggravated excitotoxic motoneuron death by two mechanisms: an increase of AMPA receptor conductance and an elevation of the Ca2+ driving force through a partial repolarization. The Cl- influx during AMPA receptor stimulation was enhanced by coadministration of GABA. This resulted in an increased Ca2+ influx and an enhanced cell death, suggesting that concomitant GABAergic stimulation may aggravate excitotoxic motoneuron death.

GluR2-dependent properties of AMPA receptors determine the selective vulnerability of motor neurons to excitotoxicity.

AMPA receptor-mediated excitotoxicity has been implicated in the selective motor neuron loss in amyotrophic lateral sclerosis. In some culture models, motor neurons have been shown to be selectively vulnerable to AMPA receptor agonists due to Ca(2+) influx through Ca(2+)-permeable AMPA receptors. Because the absence of GluR2 in AMPA receptors renders them highly permeable to Ca(2+) ions, it has been hypothesized that the selective vulnerability of motor neurons is due to their relative deficiency in GluR2. However, conflicting evidence exists about the in vitro and in vivo expression of GluR2 in motor neurons, both at the mRNA and at the protein level. In this study, we quantified electrophysiological properties of AMPA receptors, known to be dependent on the relative abundance of GluR2: sensitivity to external polyamines, rectification index, and relative Ca(2+) permeability. Cultured rat spinal cord motor neurons were compared with dorsal horn neurons (which are resistant to excitotoxicity) and with motor neurons that survived an excitotoxic insult. Motor neurons had a higher sensitivity to external polyamines, a lower rectification index, and a higher relative Ca(2+) permeability ratio than dorsal horn neurons. These findings confirm that motor neurons are relatively deficient in GluR2. The AMPA receptor properties correlated well with each other and with the selective vulnerability of motor neurons because motor neurons surviving an excitotoxic event had similar characteristics as dorsal horn neurons. These data indicate that the relative abundance of GluR2 in functional AMPA receptors may be a major determinant of the selective vulnerability of motor neurons to excitotoxicity in vitro.

AMPA Receptor Calcium Permeability, GluR2 Expression, and Selective Motoneuron Vulnerability

AMPA receptor-mediated excitotoxicity is proposed to play a major pathogenic role in the selective motoneuron death of amyotrophic lateral sclerosis. Motoneurons have been shown in various models to be more susceptible to AMPA receptor-mediated injury than other spinal neurons. It has been hypothesized that this selective vulnerability of motoneurons is caused by the expression of highly Ca(2+)-permeable AMPA receptors and a complete or relative lack of the AMPA receptor subunit Glu receptor 2 (GluR2). The aim of this study was to quantify the relative Ca(2+) permeability of AMPA receptors and the fractional expression of GluR2 in motoneurons by combining whole-cell patch-clamp electrophysiology and single-cell RT-PCR and to compare these properties with those of dorsal horn neurons. Spinal motoneurons and dorsal horn neurons were isolated from embryonic rats and cultured on spinal astrocytes. As in previous studies, motoneurons were significantly more vulnerable to AMPA and kainate than dorsal horn neurons. However, all motoneurons expressed GluR2 mRNA ( approximately 40% of total AMPA receptor subunit mRNA), and their AMPA receptors had intermediate whole-cell relative Ca(2+) permeability (P(Ca(2+))/P(Cs(+)) approximately 0. 4). AMPA receptor P(Ca(2+))/P(Cs(+)) and the relative abundance of GluR2 varied more widely in dorsal horn neurons than in motoneurons, but the mean values did not differ significantly between the two cell populations. GluR2 was virtually completely edited at the Q/R site both in motoneurons and dorsal horn neurons. These results indicate that the selective vulnerability of motoneurons to AMPA receptor agonists is not determined solely by whole-cell relative Ca(2+) permeability of AMPA receptors.

Modulating Excitatory Synaptic Neurotransmission: Potential Treatment for Neurological Disease?

Excitatory neurotransmission at many CNS synapses depends upon AMPA-type glutamate receptors. Derangements in AMPA receptor-mediated synaptic transmission may be a contributing factor in neurological and neurodegenerative diseases and could be a target for therapeutic intervention. Drugs that positively modulate AMPA receptors by reducing AMPA receptor desensitization and/or slowing AMPA receptor deactivation, such as thiazide derivatives (cyclothiazide, diazoxide, IDRA 21) and benzoylpiperidine derivatives (1-BCP, CX516, aniracetam), facilitate AMPA receptor-mediated processes and may have beneficial therapeutic effects. For example, AMPA modulators facilitate long-term potentiation, which may be important for memory storage, and facilitate memory encoding in behavioral experiments. Thus, AMPA modulators might ameliorate memory deficits that occur in dementia, such as Alzheimer's disease. However, AMPA receptor-mediated excitotoxicity may occur with excessive AMPA receptor activation such as in seizures or ischemia, and positive AMPA modulators would promote neuronal injury under those conditions. Regardless of the ultimate clinical utility of positive AMPA modulators, their discovery and study have already provided significant insight into the physiology and structural determinants of important AMPA receptor properties. This review attempts to synthesize a variety of studies that have utilized these AMPA modulators to gain insight into fundamental as well as clinically relevant AMPA receptor-mediated processes.

AMPA receptor-mediated excitotoxicity in human NT2-N neurons results from loss of intracellular Ca2+ homeostasis following marked elevation of intracellular Na+.

Human NT2-N neurons express Ca2+-permeable alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid glutamate receptors (AMPA-GluRs) and become vulnerable to excitotoxicity when AMPA-GluR desensitization is blocked with cyclothiazide. Although the initial increase in intracellular Ca2+ levels ([Ca2+]i) was 1.9-fold greater in the presence than in the absence of cyclothiazide, Ca2+ entry via AMPA-GluRs in an early phase of the exposure was not necessary to elicit excitotoxicity in these neurons. Rather, subsequent necrosis was caused by a >40-fold rise in [Na+]i, which induced a delayed [Ca2+]i rise. Transfer of the neurons to a 5 mM Na+ medium after AMPA-GluR activation accelerated the delayed [Ca2+]i rise and intensified excitotoxicity. Low-Na+ medium-enhanced excitotoxicity was partially blocked by amiloride or dizocilpine (MK-801), and completely blocked by removal of extracellular Ca2+, suggesting that Ca2+ entry by reverse operation of Na+/Ca2+ exchangers and via NMDA glutamate receptors was responsible for the neuronal death after excessive Na+ loading. Our results serve to emphasize the central role of neuronal Na+ loading in AMPA-GluR-mediated excitotoxicity in human neurons.

AMPA receptor activation potentiated by the AMPA modulator 1-BCP is toxic to cultured rat hippocampal neurons

The benzoylpiperidine 1-(1,3-benzodioxol-5-ylcarbonyl)-piperidine (1-BCP), and related compounds, potentiate α-amino-3-hydroxy-5-methyl-4-isoxazole proprionic acidergic (AMPAergic) synaptic currents in central neurons, and improve performance of rodents and humans on learning and memory tasks. Their physiological actions are similar but not identical to thiazides, which also enhance AMPAergic synaptic responses and improve performance of rats in water-maze and passive- avoidance tests. Thiazides also dramatically increase AMPA receptor-mediated neuronal death in vitro and in vivo. Here it was evaluated whether 1-BCP potentiated AMPA receptor-mediated excitotoxicity in hippocampal neuron cultures. Glutamate+MK 801 (to block NMDA receptors)+1 mM 1-BCP produced neuronal death that was reversed by 10 μM 2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo(F)quinoxaline (NBQX), a selective AMPA receptor antagonist. 1-BCP and drugs with similar activities can facilitate AMPA receptor-mediated excitotoxicity.