Effect In Cortical Neurons Research Articles

Viscolin-mediated antiapoptotic and neuroprotective effects in cortical neurons exposed to oxygen-glucose deprivation and rats subjected to transient focal cerebral ischemia

ABSTRACT Objective Previously, we have successfully purified and synthesized viscolin, an agent derived from Viscum coloratum extract, which has shown significant potential in the treatment of stroke. Our study aimed to evaluate the neuroprotective effects of viscolin. Methods We first assessed the cytotoxicity of viscolin on primary neuronal cultures and determined its antioxidant and radical scavenging properties. Subsequently, we identified the optimal dose-response of viscolin in protecting against glutamate-induced neurotoxicity. Results Our results demonstrated that viscolin at a concentration of 10 μM effectively reduced neuronal cell death up to 6 hours after glutamate-induced neurotoxicity. Additionally, we investigated the therapeutic window of opportunity and the potential of viscolin in preventing necrotic and apoptotic damage in cultured neurons exposed to oxygen glucose deprivation-induced neurotoxicity. Our findings showed that viscolin treatment significantly reduced DNA breakage, prevented the release of cytochrome c from mitochondria to cytosol, increased the expression of anti-apoptotic protein Bcl-2, decreased the expression of pro-apoptotic protein Bax, and reduced the number of TUNEL-positive cells. Additionally, our in vivo investigation demonstrated a reduction in brain infarction following middle cerebral artery occlusion. Conclusion Viscolin has potential utility as a therapeutic agent in the treatment of stroke.

Menthol exerts TRPM8-independent antiepileptic effects in prefrontal cortex pyramidal neurons

Menthol is a natural compound that evokes cold sensations by activating TRPM8 channels in peripheral sensory receptors. Little is known about the effects of this compound on brain neurons. It has been shown previously that menthol exerts antiepileptic effects in hippocampal neurons by enhancing GABA receptors. The aim of this patch-clamp study was to assess the effects of menthol on sodium currents, action potentials and epileptiform events in cortical neurons.Menthol inhibited fast voltage-gated sodium channels and neuronal excitability defined as the number of action potentials per depolarization step. The influence of menthol on epileptic events was also assessed in this study. Interictal epileptiform events lasting <2 s were recorded in zero magnesium high potassium proepileptic extracellular solution. The frequency of these epileptiform events was inhibited by menthol (200 µM). Ictal epileptic events lasting >100 s were recorded in zero magnesium proepileptic extracellular solution containing 4-AP. The frequency of these ictal events was potently decreased by menthol. TRPM8 channels were not involved in the inhibitory effect of menthol on ictal events because epileptic discharges persisted in the presence of the TRPM8 inhibitor AMTB. Moreover, ictal events were inhibited by therapeutic concentrations of the antiepileptic drug carbamazepine. Menthol and carbamazepine inhibited ictal events to a similar extent.This study showed that menthol exerts antiepileptic effects in cortical neurons.

KCC2 Regulates Dendritic Spine Formation in a Brain-Region Specific and BDNF Dependent Manner.

KCC2 is the major chloride extruder in neurons. The spatiotemporal regulation of KCC2 expression orchestrates the developmental shift towards inhibitory GABAergic drive and the formation of glutamatergic synapses. Whether KCC2’s role in synapse formation is similar in different brain regions is unknown. First, we found that KCC2 subcellular localization, but not overall KCC2 expression levels, differed between cortex and hippocampus during the first postnatal week. We performed site-specific in utero electroporation of KCC2 cDNA to target either hippocampal CA1 or somatosensory cortical pyramidal neurons. We found that a premature expression of KCC2 significantly decreased spine density in CA1 neurons, while it had the opposite effect in cortical neurons. These effects were cell autonomous, because single-cell biolistic overexpression of KCC2 in hippocampal and cortical organotypic cultures also induced a reduction and an increase of dendritic spine density, respectively. In addition, we found that the effects of its premature expression on spine density were dependent on BDNF levels. Finally, we showed that the effects of KCC2 on dendritic spine were dependent on its chloride transporter function in the hippocampus, contrary to what was observed in cortex. Altogether, these results demonstrate that KCC2 regulation of dendritic spine development, and its underlying mechanisms, are brain-region specific.

Designing Dual Transglutaminase 2/Histone Deacetylase Inhibitors Effective at Halting Neuronal Death.

In recent years there has been a clear consensus that neurodegenerative conditions can be better treated through concurrent modulation of different targets. Herein we report that combined inhibition of transglutaminase 2 (TG2) and histone deacetylases (HDACs) synergistically protects against toxic stimuli mediated by glutamate. Based on these findings, we designed and synthesized a series of novel dual TG2-HDAC binding agents. Compound 3 [(E)-N-hydroxy-5-(3-(4-(3-oxo-3-(pyridin-3-yl)prop-1-en-1-yl)phenyl)thioureido)pentanamide] emerged as the most interesting of the series, being able to inhibit TG2 and HDACs both in vitro (TG2 IC50 =13.3±1.5 μm, HDAC1 IC50 =3.38±0.14 μm, HDAC6 IC50 =4.10±0.13 μm) and in cell-based assays. Furthermore, compound 3 does not exert any toxic effects in cortical neurons up to 50 μm and protects neurons against toxic insults induced by glutamate (5 mm) with an EC50 value of 3.7±0.5 μm.

Suppression and Contrast Normalization in Motion Processing

Sensory neurons are activated by a range of stimuli to which they are said to be tuned. Usually, they are also suppressed by another set of stimuli that have little effect when presented in isolation. The interactions between preferred and suppressive stimuli are often quite complex and vary across neurons, even within a single area, making it difficult to infer their collective effect on behavioral responses mediated by activity across populations of neurons. Here, we investigated this issue by measuring, in human subjects (three males), the suppressive effect of static masks on the ocular following responses induced by moving stimuli. We found a wide range of effects, which depend in a nonlinear and nonseparable manner on the spatial frequency, contrast, and spatial location of both stimulus and mask. Under some conditions, the presence of the mask can be seen as scaling the contrast of the driving stimulus. Under other conditions, the effect is more complex, involving also a direct scaling of the behavioral response. All of this complexity at the behavioral level can be captured by a simple model in which stimulus and mask interact nonlinearly at two stages, one monocular and one binocular. The nature of the interactions is compatible with those observed at the level of single neurons in primates, usually broadly described as divisive normalization, without having to invoke any scaling mechanism.SIGNIFICANCE STATEMENT The response of sensory neurons to their preferred stimulus is often modulated by stimuli that are not effective when presented alone. Individual neurons can exhibit multiple modulatory effects, with considerable variability across neurons even in a single area. Such diversity has made it difficult to infer the impact of these modulatory mechanisms on behavioral responses. Here, we report the effects of a stationary mask on the reflexive eye movements induced by a moving stimulus. A model with two stages, each incorporating a divisive modulatory mechanism, reproduces our experimental results and suggests that qualitative variability of masking effects in cortical neurons might arise from differences in the extent to which such effects are inherited from earlier stages.

TIGAR contributes to ischemic tolerance induced by cerebral preconditioning through scavenging of reactive oxygen species and inhibition of apoptosis.

Previous study showed that TIGAR (TP53-induced glycolysis and apoptosis regulator) protected ischemic brain injury via enhancing pentose phosphate pathway (PPP) flux and preserving mitochondria function. This study was aimed to study the role of TIGAR in cerebral preconditioning. The ischemic preconditioning (IPC) and isoflurane preconditioning (ISO) models were established in primary cultured cortical neurons and in mice. Both IPC and ISO increased TIGAR expression in cortical neurons. Preconditioning might upregulate TIGAR through SP1 transcription factor. Lentivirus mediated knockdown of TIGAR significantly abolished the ischemic tolerance induced by IPC and ISO. ISO also increased TIGAR in mouse cortex and hippocampus and alleviated subsequent brain ischemia-reperfusion injury, while the ischemic tolerance induced by ISO was eliminated with TIGAR knockdown in mouse brain. ISO increased the production of NADPH and glutathione (GSH), and scavenged reactive oxygen species (ROS), while TIGAR knockdown decreased GSH and NADPH production and increased the level of ROS. Supplementation of ROS scavenger NAC and PPP product NADPH effectively rescue the neuronal injury caused by TIGAR deficiency. Notably, TIGAR knockdown inhibited ISO-induced anti-apoptotic effects in cortical neurons. These results suggest that TIGAR participates in the cerebral preconditioning through reduction of ROS and subsequent cell apoptosis.

Melatonin-sulforaphane hybrid ITH12674 induces neuroprotection in oxidative stress conditions by a 'drug-prodrug' mechanism of action.

Neurodegenerative diseases are a major problem afflicting ageing populations; however, there are no effective treatments to stop their progression. Oxidative stress and neuroinflammation are common factors in their pathogenesis. Nuclear factor (erythroid-derived 2)-like 2 (Nrf2) is the master regulator of oxidative stress, and melatonin is an endogenous hormone with antioxidative properties that reduces its levels with ageing. We have designed a new compound that combines the effects of melatonin with Nrf2 induction properties, with the idea of achieving improved neuroprotective properties. Compound ITH12674 is a hybrid of melatonin and sulforaphane designed to exert a dual drug-prodrug mechanism of action. We obtained the proposed hybrid in a single step. To test its neuroprotective properties, we used different in vitro models of oxidative stress related to neurodegenerative diseases and brain ischaemia. ITH12674 showed an improved neuroprotective profile compared to that of melatonin and sulforaphane. ITH12674 (i) mediated a concentration-dependent protective effect in cortical neurons subjected to oxidative stress; (ii) decreased reactive oxygen species production; (iii) augmented GSH concentrations in cortical neurons; (iv) enhanced the Nrf2-antioxidant response element transcriptional response in transfected HEK293T cells; and (v) protected organotypic cultures of hippocampal slices subjected to oxygen and glucose deprivation and re-oxygenation from stress by increasing the expression of haem oxygenase-1 and reducing free radical production. ITH12674 combines the signalling pathways of the parent compounds to improve its neuroprotective properties. This opens a new line of research for such hybrid compounds to treat neurodegenerative diseases.

Rhodiola rosea Extract Protects Human Cortical Neurons against Glutamate and Hydrogen Peroxide‐induced Cell Death Through Reduction in the Accumulation of Intracellular Calcium

The aim of this study was to investigate the neuroprotective effects of a titolated extract from Rhodiola rosea L. (RrE) and of salidroside (Sa), one of the major biologically active compounds extracted from this medicinal plant, against oxidative stressor hydrogen peroxide (H₂O₂) and glutamate (GLU)-induced cell apoptosis in a human cortical cell line (HCN 1-A) maintained in culture. The results obtained indicate that exposure of differentiated HCN 1-A neurons to GLU or H₂O₂ resulted in concentration-dependent cell death. A 24 h pre-treatment with RrE significantly increased cell survival and significantly prevented the plasma membrane damage and the morphological disruption caused by GLU or H₂O₂, indicating that neurons treated with RrE were protected from the neurotoxicity induced by the oxidative stressor used. In addition, RrE significantly reduced H₂O₂ or GLU-induced elevation of intracellular free Ca²⁺ concentration. The results obtained have also shown that Sa caused similar effects in all experimental models used; however, the potency of the action was lower than that of the extract containing corresponding quantities of Sa. These findings indicate that RrE has a neuroprotective effect in cortical neurons and suggest that the antioxidant activity of the RrE, due to the structural features of the synergic active principles they contain, may be responsible for its ability to stabilize cellular Ca²⁺ homeostasis.

Adenosine A1 receptor-mediated transactivation of the EGF receptor produces a neuroprotective effect on cortical neurons in vitro

To understand the mechanism of the transactivation of the epidermal growth factor receptor (EGFR) mediated by the adenosine A(1) receptor (A(1)R). Primary cultured rat cortical neurons subjected to oxygen-glucose deprivation (OGD) and HEK293/A(1)R cells were treated with the A(1)R-specific agonist N(6)-cyclopentyladenosine (CPA). Phospho-EGFR, Akt, and ERK1/2 were observed by Western blot. An interaction between EGFR and A(1)R was detected using immunoprecipitation and immunocytochemistry. The A(1)R agonist CPA causes protein kinase B (Akt) activation and protects primary cortical neurons from oxygen-glucose deprivation (OGD) insult. A(1)R and EGFR co-localize in the membranes of neurons and form an immunocomplex. A(1)R stimulation induces significant EGFR phosphorylation via a PI3K and Src kinase signaling pathway; this stimulation provides a neuroprotective effect in cortical neurons. CPA leads to sustained phosphorylation of extracellularly regulated kinases 1 and 2 (ERK1/2) in cortical neurons, but only to transient phosphorylation in HEK 293/A(1)R cells. The response to the A(1)R agonist is mediated primarily through EGFR transactivation that is dependent on pertussis toxin (PTX)-sensitive G(i) protein and metalloproteases in HEK 293/A(1)R. A(1)R-mediated EGFR transactivation confers a neuroprotective effect in primary cortical neurons. PI3 kinase and Src kinase play pivotal roles in this response.Acta Pharmacologica Sinica (2009) 30: 889-898; doi: 10.1038/aps.2009.80.

Integrin regulation of cytoplasmic calcium in excitatory neurons depends upon glutamate receptors and release from intracellular stores

Integrins regulate cytoplasmic calcium levels ([Ca 2+]i) in various cell types but information on activities in neurons is limited. The issue is of current interest because of the evidence that both integrins and changes in [Ca 2+]i are required for Long-Term Potentiation. Accordingly, the present studies evaluated integrin ligand effects in cortical neurons. Integrin ligands or α5β1 integrin activating antisera rapidly increased [Ca 2+]i with effects greater in glutamatergic than GABAergic neurons, absent in astroglia, and blocked by β1 integrin neutralizing antisera and the tyrosine kinase antagonist genistein. Increases depended upon extracellular calcium and intracellular store release. Ligand-induced effects were reduced by voltage-sensitive calcium channel and NMDA receptor antagonists, but blocked by tetrodotoxin or AMPA receptor antagonists. These results indicate that integrin ligation triggers AMPA receptor/depolarization-dependent calcium influx followed by intracellular store release and suggest the possibility that integrin modulation of activity-induced changes in [Ca 2+]i contributes importantly to lasting synaptic plasticity in forebrain neurons.

Protective effects of lipopolysaccharide preconditioning against nitric oxide neurotoxicity

We have characterized lipopolysaccharide (LPS) preconditioning-induced neuroprotective mechanisms against nitric oxide (NO) toxicity. Pretreatment of rat cortical cultures with LPS attenuated neurotoxicity of NO donors, including sodium nitroprusside (SNP) and diethylamine NONOate (NONOate). A transiently increased expression of endothelial nitric oxide synthase (eNOS) accompanied by an increase in NO production was observed during LPS preconditioning. Application of NOS inhibitors including L-N(5)-(1-iminoethyl)-ornithine (L-NIO) and L-nitroarginine methylester (L-NAME) abolished LPS-dependent protection against SNP toxicity. The LPS effect was also blocked by KT5823, an inhibitor of cGMP-dependent protein kinase (PKG). Consistently, application of 8-bromo-cyclic GMP (8-Br-cGMP), a slowly degradable cGMP analogue capable of PKG activation, was neuroprotective. LPS preconditioning resulted in a heightened neuronal expression of Bcl-2 protein that was abolished by L-NAME and KT5823, the respective inhibitors of NOS and PKG. Together, our results reveal the signaling cascade of "LPS --> eNOS --> NO --> cGMP/PKG --> Bcl-2" that might have contributed to the LPS protective effects in cortical neurons.

SNAP, a NO donor, induces cellular protection only when cortical neurons are submitted to some aggression process

Nitric oxide is a versatile molecule, which plays important physiological and pathological roles. Its protective and toxic actions have been already evidenced in several cell types. However, the protective effect in cortical neurons remains elusive. In this work, we demonstrate that the NO-donor SNAP may induce both neuroprotection and neurotoxicity in this sort of cells. The protective effect of NO was evidenced when cortical neurons were exposed to deleterious conditions, such as serum deprivation. Serum deprivation induces apoptotic cortical neuron death through a caspase-dependent mechanism. Under these conditions, SNAP was able to oppose cell death through both caspase-3 inhibition and/or increase of antiapoptotic protein levels (Bcl-2 and Bcl-x L). On the other hand, in a normally serum-supplemented medium, high dose of SNAP behaves as a neurotoxic agent, through a mechanism which involves caspase-3 activation.

Tetrahydrocannabinol-induced neurotoxicity depends on CB1 receptor-mediated c-Jun N-terminal kinase activation in cultured cortical neurons.

Delta9-Tetrahydrocannabinol (THC), the main psychoactive ingredient of marijuana, induces apoptosis in cultured cortical neurons. THC exerts its apoptotic effects in cortical neurons by binding to the CB1 cannabinoid receptor. The CB1 receptor has been shown to couple to the stress-activated protein kinase, c-Jun N-terminal kinase (JNK). However, the involvement of specific JNK isoforms in the neurotoxic properties of THC remains to be established. The present study involved treatment of rat cultured cortical neurons with THC (0.005-50 microM), and combinations of THC with the CB1 receptor antagonist, AM 251 (10 microM) and pertussis toxin (PTX; 200 ng ml-1). Antisense oligonucleotides (AS) were used to deplete neurons of JNK1 and JNK2 in order to elucidate their respective roles in THC signalling. Here we report that THC induces the activation of JNK via the CB1 receptor and its associated G-protein, Gi/o. Treatment of cultured cortical neurons with THC resulted in a differential timeframe of activation of the JNK1 and JNK2 isoforms. Use of specific JNK1 and JNK2 AS identified activation of caspase-3 and DNA fragmentation as downstream consequences of JNK1 and JNK2 activation. The results from this study demonstrate that activation of the CB1 receptor induces JNK and caspase-3 activation, an increase in Bax expression and DNA fragmentation. The data demonstrate that the activation of both JNK1 and JNK2 isoforms is central to the THC-induced activation of the apoptotic pathway in cortical neurons.

Intracellularly recorded responses of neurons of the motor cortex of awake cats to presentations of Pavlovian conditioned and unconditioned stimuli

The electrical responses to a conditioned stimulus (click CS) and an unconditioned stimulus (glabella tap US) were studied in single units of the pericruciate cortex of awake cats. There has been no previous direct, in vivo characterization of the intracellular effects in cortical neurons of a CS and US used for associative Pavlovian conditioning. Earlier studies showed that ablation of the pericruciate cortex prevented the development of short latency blink CRs produced by associative pairing of these stimuli. Both the CS and the US produced depolarizing EPSPs and increases in spike discharge in intracellularly recorded units. The magnitude of the EPSPs was greater in response to the tap US than to the click CS, and the degree of unit discharge in response to the tap US was greater than that to the click CS. The onset latencies of the spike responses were distributed in three ranges. For click CS the ranges were 6–15, 20–35 and 40–85 ms. For tap US the ranges were 6–25, 30–45 and 50–85 ms. An additional response was observed in the period 0.5–6.0 ms after tap onset. It was thought to be elicited mechanically by vibration of the electrode tip following tap delivery. Pentobarbital anesthesia abolished the unconditioned motor response to tap, but failed to abolish the neuronal responses in any of the latency ranges, suggesting that the responses were not produced by feedback from the movement. Both the CS and the US are needed for the development of blink conditioning, and are distinguished behaviorally by the US producing an unconditioned motor response whose form resembles that of the conditioned response which develops after the stimuli are paired. Both the click CS and the tap US also produced hyperpolarizing IPSPs. Injection of steady, hyperpolarizing current disclosed two types of IPSPs in response to the tap US. One reversed with hyperpolarization; the other increased in magnitude with hyperpolarization. The magnitude of inhibition, measured by reduced discharge, was greater in response to the click CS than to the tap US. We conclude that the major differences between effects of this CS and US on cells of the motor cortex of cats are that the CS elicits less activity than the US and has a larger inhibiting effect. The US elicits greater depolarization than does the CS, as well as an initial discharge component of greater magnitude and longer duration.

Metabotropic Glutamate Receptors, PLCbeta 1 Signalling and Hippocampal Epileptiform Discharges.

Group I Metabotropic Glutamate Receptors Elicit Epileptiform Discharges in the Hippocampus Through PLCbeta1 Signaling Chuang SC, Bianchi R, Kim D, Shin HS, Wong RK J Neurosci 2001;21:6387–6394 Activation of metabotropic glutamate receptors (mGluRs) produces multiple effects in cortical neurons, resulting in the emergence of network activities including epileptiform discharges. The cellular mechanisms underlying such network responses are largely unknown. We examined the properties of group I mGluR-mediated cellular responses in CA3 neurons and attempted to determine their role in the generation of the network activities. Group I mGluR stimulation causes depolarization of hippocampal neurons. This depolarization is primarily mediated by two sets of conductance change: the opening of a voltage-dependent cationic conductance (mediating I(mGluR(V))) and the closing of a voltage-independent (background) K(+) conductance. I(mGluR(V)) was no longer elicited by group I mGluR agonists in the presence of U73122, a phospholipase C (PLC) blocker. Also, the current could not be activated in hippocampal CA3 neurons from PLCbeta1 knock-out mice. In contrast, suppression of PLC signaling did not affect the group I mGluR-mediated suppression of background K(+) conductance. Thus, the suppression of the background K(+) conductance occurred upstream to PLC activation, whereas the generation of I(mGluR(V)) occurred downstream to PLC activation. Group I mGluR agonists normally elicited rhythmic single cell and population burst responses in the CA3 neurons. In the absence of an I(mGluR(V)) response, CA3 neurons in slices prepared from PLCbeta1–/– mutant mice could no longer generate these responses. The results suggest that I(mGluR(V)) expression in CA3 hippocampal neuron is PLCbeta1-dependent and that I(mGluR(V)) plays a necessary role in the generation of rhythmic single cell bursts and synchronized epileptiform discharges in the CA3 region of the hippocampus.

Group I Metabotropic Glutamate Receptors Elicit Epileptiform Discharges in the Hippocampus through PLCβ1 Signaling

Activation of metabotropic glutamate receptors (mGluRs) produces multiple effects in cortical neurons, resulting in the emergence of network activities including epileptiform discharges. The cellular mechanisms underlying such network responses are largely unknown. We examined the properties of group I mGluR-mediated cellular responses in CA3 neurons and attempted to determine their role in the generation of the network activities. Group I mGluR stimulation causes depolarization of hippocampal neurons. This depolarization is primarily mediated by two sets of conductance change: the opening of a voltage-dependent cationic conductance (mediating I(mGluR(V))) and the closing of a voltage-independent (background) K(+) conductance. I(mGluR(V)) was no longer elicited by group I mGluR agonists in the presence of U73122, a phospholipase C (PLC) blocker. Also, the current could not be activated in hippocampal CA3 neurons from PLCbeta1 knock-out mice. In contrast, suppression of PLC signaling did not affect the group I mGluR-mediated suppression of background K(+) conductance. Thus, the suppression of the background K(+) conductance occurred upstream to PLC activation, whereas the generation of I(mGluR(V)) occurred downstream to PLC activation. Group I mGluR agonists normally elicited rhythmic single cell and population burst responses in the CA3 neurons. In the absence of an I(mGluR(V)) response, CA3 neurons in slices prepared from PLCbeta1-/- mutant mice could no longer generate these responses. The results suggest that I(mGluR(V)) expression in CA3 hippocampal neuron is PLCbeta1-dependent and that I(mGluR(V)) plays a necessary role in the generation of rhythmic single cell bursts and synchronized epileptiform discharges in the CA3 region of the hippocampus.

Transcriptional Regulation of the GluR2 Gene: Neural-Specific Expression, Multiple Promoters, and Regulatory Elements

To understand how neurons control the expression of the AMPA receptor subunit GluR2, we cloned the 5' proximal region of the rat gene and investigated GluR2 promoter activity by transient transfection. RNase protection and primer extension of rat brain mRNA revealed multiple transcription initiation sites from -340 to -481 bases upstream of the GluR2 AUG codon. The relative use of 5' start sites was different in cortex and cerebellum, indicating complexity of GluR2 transcript expression among different sets of neurons. When GluR2 promoter activity was investigated by plasmid transfection into cultured cortical neurons, cortical glia, and C6 glioma cells, the promoter construct with the strongest activity, per transfected cell, was 29.4-fold (+/- 3.7) more active in neurons than in non-neural cells. Immunostaining of cortical cultures showed that >97% of the luciferase-positive cells also expressed the neuronal marker MAP-2. Evaluation of internal deletion and substitution mutations identified a functional repressor element I RE1-like silencer and functional Sp1 and nuclear respiratory factor-1 (NRF-1) elements within a GC-rich proximal GluR2 promoter region. The GluR2 silencer reduced promoter activity in glia and non-neuronal cell lines by two- to threefold, was without effect in cortical neurons, and could bind the RE1-silencing transcription factor (REST) because cotransfection of REST into neurons reduced GluR2 promoter activity in a silencer-dependent manner. Substitution of the GluR2 silencer by the homologous NaII RE1 silencer further reduced GluR2 promoter activity in non-neuronal cells by 30-47%. Maximal positive GluR2 promoter activity required both Sp1 and NRF-1 cis elements and an interelement nucleotide bridge sequence. These results indicate that GluR2 transcription initiates from multiple sites, is highly neuronal selective, and is regulated by three regulatory elements in the 5' proximal promoter region.

A physiological correlate of the pulfrich effect in cortical neurons of the cat

When a swinging pendulum is viewed with a light-attenuating filter before one eye, the pendulum bob is perceived to move in an elliptical path in depth. It is believed that the filter causes this illusion, the Pulfrich effect, by delaying processing of the image in the filtered eye relative to that of the unfiltered eye. We sought a physiological correlate of this effect by studying binocular integration in cortical neurons of cats while they viewed moving stimuli. Special attention was focused on single unit disparity tuning because it is widely believed that depth perception is related to the responses of disparity selective neurons in visual cortex. We found that placing a filter before one of the cat's eyes produced a temporal delay in the cortical response. The temporal delay was always associated with a shift in the neuron's spatial disparity tuning. The observed temporal delays and disparity shifts are comparable with the magnitude of the Pulfrich effect in humans.