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1.
J Neurophysiol ; 131(5): 876-890, 2024 05 01.
Artículo en Inglés | MEDLINE | ID: mdl-38568510

RESUMEN

At the heart of the prefrontal network is the mediodorsal (MD) thalamus. Despite the importance of MD in a broad range of behaviors and neuropsychiatric disorders, little is known about the physiology of neurons in MD. We injected the retrograde tracer cholera toxin subunit B (CTB) into the medial prefrontal cortex (mPFC) of adult wild-type mice. We prepared acute brain slices and used current clamp electrophysiology to measure and compare the intrinsic properties of the neurons in MD that project to mPFC (MD→mPFC neurons). We show that MD→mPFC neurons are located predominantly in the medial (MD-M) and lateral (MD-L) subnuclei of MD. MD-L→mPFC neurons had shorter membrane time constants and lower membrane resistance than MD-M→mPFC neurons. Relatively increased hyperpolarization-activated cyclic nucleotide-gated (HCN) channel activity in MD-L neurons accounted for the difference in membrane resistance. MD-L neurons had a higher rheobase that resulted in less readily generated action potentials compared with MD-M→mPFC neurons. In both cell types, HCN channels supported generation of burst spiking. Increased HCN channel activity in MD-L neurons results in larger after-hyperpolarization potentials compared with MD-M neurons. These data demonstrate that the two populations of MD→mPFC neurons have divergent physiologies and support a differential role in thalamocortical information processing and potentially behavior.NEW & NOTEWORTHY To realize the potential of circuit-based therapies for psychiatric disorders that localize to the prefrontal network, we need to understand the properties of the populations of neurons that make up this network. The mediodorsal (MD) thalamus has garnered attention for its roles in executive functioning and social/emotional behaviors mediated, at least in part, by its projections to the medial prefrontal cortex (mPFC). Here, we identify and compare the physiology of the projection neurons in the two MD subnuclei that provide ascending inputs to mPFC in mice. Differences in intrinsic excitability between the two populations of neurons suggest that neuromodulation strategies targeting the prefrontal thalamocortical network will have differential effects on these two streams of thalamic input to mPFC.


Asunto(s)
Núcleo Talámico Mediodorsal , Ratones Endogámicos C57BL , Corteza Prefrontal , Animales , Corteza Prefrontal/fisiología , Corteza Prefrontal/citología , Ratones , Núcleo Talámico Mediodorsal/fisiología , Núcleo Talámico Mediodorsal/citología , Masculino , Neuronas/fisiología , Vías Nerviosas/fisiología , Potenciales de Acción/fisiología , Canales Regulados por Nucleótidos Cíclicos Activados por Hiperpolarización/fisiología , Canales Regulados por Nucleótidos Cíclicos Activados por Hiperpolarización/metabolismo
2.
Genome Res ; 31(8): 1447-1461, 2021 08.
Artículo en Inglés | MEDLINE | ID: mdl-34301626

RESUMEN

A wealth of genetic information is available describing single-nucleotide variants in the human population that appear to be well-tolerated and in and of themselves do not confer disease. These variant data sets contain signatures about the protein structure-function relationships and provide an unbiased view of various protein functions in the context of human health. This information can be used to determine regional intolerance to variation, defined as the missense tolerance ratio (MTR), which is an indicator of stretches of the polypeptide chain that can tolerate changes without compromising protein function in a manner that impacts human health. This approach circumvents the lack of comprehensive data by averaging the data from adjacent residues on the polypeptide chain. We reasoned that many motifs in proteins consist of nonadjacent residues, but together function as a unit. We therefore developed an approach to analyze nearest neighbors in three-dimensional space as determined by crystallography rather than on the polypeptide chain. We used members of the GRIN gene family that encode subunits of NMDA-type ionotropic glutamate receptors (iGluRs) to exemplify the differences between these methods. Our method, 3DMTR, provides new information about regions of intolerance within iGluRs, allows consideration of protein-protein interfaces in multimeric proteins, and moves this important research tool from one-dimensional analysis to a structurally relevant tool. We validate the improved 3DMTR score by showing that it more accurately classifies the functional consequences of a set of newly measured and published point mutations of Grin family genes than existing methods.


Asunto(s)
Biología Computacional , Proteínas , Biología Computacional/métodos , Humanos , Mutación Missense , Proteínas/genética
3.
J Pharmacol Exp Ther ; 379(1): 41-52, 2021 10.
Artículo en Inglés | MEDLINE | ID: mdl-34493631

RESUMEN

We describe a clinical candidate molecule from a new series of glutamate N-methyl-d-aspartate receptor subunit 2B-selective inhibitors that shows enhanced inhibition at extracellular acidic pH values relative to physiologic pH. This property should render these compounds more effective inhibitors of N-methyl-d-aspartate receptors at synapses responding to a high frequency of action potentials, since glutamate-containing vesicles are acidic within their lumen. In addition, acidification of penumbral regions around ischemic tissue should also enhance selective drug action for improved neuroprotection. The aryl piperazine we describe here shows strong neuroprotective actions with minimal side effects in preclinical studies. The clinical candidate molecule NP10679 has high oral bioavailability with good brain penetration and is suitable for both intravenous and oral dosing for therapeutic use in humans. SIGNIFICANCE STATEMENT: This study identifies a new series of glutamate N-methyl-d-aspartate (NMDA) receptor subunit 2B-selective negative allosteric modulators with properties appropriate for clinical advancement. The compounds are more potent at acidic pH, associated with ischemic tissue, and this property should increase the therapeutic safety of this class by improving efficacy in affected tissue while sparing NMDA receptor block in healthy brain.


Asunto(s)
Encéfalo/efectos de los fármacos , Encéfalo/metabolismo , Antagonistas de Aminoácidos Excitadores/administración & dosificación , Antagonistas de Aminoácidos Excitadores/metabolismo , Receptores de N-Metil-D-Aspartato/antagonistas & inhibidores , Receptores de N-Metil-D-Aspartato/metabolismo , Ácidos , Administración Oral , Animales , Disponibilidad Biológica , Relación Dosis-Respuesta a Droga , Femenino , Concentración de Iones de Hidrógeno , Masculino , Ratones , Ratones Endogámicos C57BL , Xenopus laevis
4.
Proc Natl Acad Sci U S A ; 115(51): 13099-13104, 2018 12 18.
Artículo en Inglés | MEDLINE | ID: mdl-30498030

RESUMEN

The mammalian retina contains an autonomous circadian clock system that controls many physiological functions within this tissue. Previous studies on young mice have reported that removal of the key circadian clock gene Bmal1 from the retina affects the circadian regulation of visual function, but does not affect photoreceptor viability. Because dysfunction in the circadian system is known to affect cell viability during aging in other systems, we compared the effect of Bmal1 removal from the retina on visual function, inner retinal structure, and photoreceptor viability in young (1 to 3 months) and aged (24 to 26 months) mice. We found that removal of Bmal1 from the retina significantly affects visual information processing in both rod and cone pathways, reduces the thickness of inner retinal nuclear and plexiform layers, accelerates the decline of visual functions during aging, and reduces the viability of cone photoreceptors. Our results thus suggest that circadian clock dysfunction, caused by genetic or other means, may contribute to the decline of visual function during development and aging.


Asunto(s)
Factores de Transcripción ARNTL/fisiología , Envejecimiento/patología , Ritmo Circadiano , Retina/patología , Células Fotorreceptoras Retinianas Conos/patología , Visión Ocular , Envejecimiento/metabolismo , Animales , Relojes Circadianos , Regulación de la Expresión Génica , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Retina/metabolismo , Células Fotorreceptoras Retinianas Conos/metabolismo
5.
Neurocrit Care ; 20(1): 119-31, 2014 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-24420693

RESUMEN

BACKGROUND: Despite intensive research, neurological morbidity from delayed cerebral ischemia remains common after aneurysmal subarachnoid hemorrhage (SAH). In the current study, we evaluate the neuroprotective effects of a pH-dependent GluN2B subunit-selective NMDA receptor antagonist in a murine model of SAH. METHODS: Following induction of SAH, 12 ± 2 week old male C57-BL/6 mice received NP10075, a pH-dependent NMDA receptor antagonist, or vehicle. In a separate series of experiments, NP10075 and the non-pH sensitive NMDA antagonist, NP10191, were administered to normoglycemic and hyperglycemic mice. Both histological (right middle cerebral artery diameter, NeuN, and Fluoro-Jade B staining) and functional endpoints (rotarod latency and neuroseverity score) were evaluated to assess the therapeutic benefit of NP10075. RESULTS: Administration of NP10075 was well tolerated and had minimal hemodynamic effects following SAH. Administration of the pH-sensitive NMDA antagonist NP10075, but not NP10191, was associated with a durable improvement in the functional performance of both normoglycemic and hyperglycemic animals. NP10075 was also associated with a reduction in vasospasm in the middle cerebral artery associated with hemorrhage. There was no significant difference between treatment with nimodipine + NP10075, as compared to NP10075 alone. CONCLUSIONS: These data demonstrate that use of a pH-dependent NMDA antagonist has the potential to work selectively in areas of ischemia known to undergo acidic pH shifts, and thus may be associated with selective regional efficacy and fewer behavioral side effects than non-selective NMDA antagonists.


Asunto(s)
Fármacos Neuroprotectores/farmacología , Receptores de N-Metil-D-Aspartato/antagonistas & inhibidores , Hemorragia Subaracnoidea/tratamiento farmacológico , Animales , Conducta Animal/fisiología , Bloqueadores de los Canales de Calcio/farmacología , Modelos Animales de Enfermedad , Concentración de Iones de Hidrógeno , Hiperglucemia/inducido químicamente , Imagen por Resonancia Magnética , Masculino , Ratones , Ratones Endogámicos C57BL , Nimodipina/farmacología , Distribución Aleatoria , Hemorragia Subaracnoidea/complicaciones
6.
J Neurotrauma ; 38(20): 2896-2906, 2021 10 15.
Artículo en Inglés | MEDLINE | ID: mdl-34353120

RESUMEN

Pressure waves from explosions or other traumatic events can damage the neurons of the eye and visual centers of the brain, leading to functional loss of vision. There are currently few treatments for such injuries that can be deployed rapidly to mitigate damage. Brain-derived neurotrophic factor (BDNF) and activation of its receptor tropomycin-related kinase B (TrkB) have neuroprotective effects in a number of degeneration models. Small molecule activators of TrkB, such as N-[2-(5-hydroxy-1H-indol-3-yl)ethyl]-2-oxopiperidine-3-carboxamide (HIOC), cross the blood-brain and blood-retina barriers after systemic administration. We characterize the effects of blast-induced ocular trauma on retinal and visual function. We show that systemic administration of HIOC, a potent small molecule activator of the BDNF/TrkB receptor, preserves visual function in mice exposed to ocular blast injury. The HIOC treatment for one week preserves visual function for at least four months. The HIOC treatment effectively protected vision when the initial dose was administered up to 3 h after blast, but not if the initial treatment was delayed for 24 h. We provide evidence that the therapeutic effect of HIOC is mediated by activation of BDNF/TrkB receptors. The results indicate that HIOC may be useful for managing ocular blast injury and other forms of traumatic optic neuropathy.


Asunto(s)
Traumatismos por Explosión/complicaciones , Ceguera/tratamiento farmacológico , Ceguera/etiología , Lesiones Oculares/complicaciones , Traumatismos del Nervio Óptico/tratamiento farmacológico , Traumatismos del Nervio Óptico/etiología , Receptor trkB/agonistas , Animales , Barrera Hematoencefálica/metabolismo , Barrera Hematorretinal/metabolismo , Factor Neurotrófico Derivado del Encéfalo/metabolismo , Ratones , Ratones Endogámicos C57BL , Neuroprotección , Fármacos Neuroprotectores/farmacología , Retina/fisiopatología , Tiempo de Tratamiento , Resultado del Tratamiento
7.
Invest Ophthalmol Vis Sci ; 61(6): 24, 2020 06 03.
Artículo en Inglés | MEDLINE | ID: mdl-32531058

RESUMEN

Purpose: The present study tested the hypothesis that connexin-36 (Cx36) and gap junctions between photoreceptor cells contribute to the circadian rhythm of the photopic electroretinogram (ERG) b-wave amplitude. Methods: Cone-specific disruption of Cx36 was obtained in mice with a floxed Gjd2 gene and human red/green pigment promoter (HRGP)-driven Cre recombinase. Standard ERG, spectral-domain optical coherence tomography (SD-OCT) and histochemical methods were used. Results: HRGPcreGjd2fl/fl mice had a selective reduction in Cx36 protein in the outer plexiform layer; no reduction in Cx36 was observed in the inner plexiform layer. Cx36 disruption had no effect on the number of cones, the thickness of the photoreceptor layer, or the scotopic ERG responses. However, there was a reduction of the photopic ERG circadian rhythm, with b-wave amplitudes in the day and the night locked in the daytime, light-adapted state. In HRGPcreGjd2+/+and Gjd2fl/fl controls, the circadian rhythm of light-adapted ERG persisted, similar to that in wild type mice. Conclusions: Cx36 regulation contributes to the circadian rhythm of light-adapted ERG; in the absence of photoreceptor gap junctions, mice appear to be in a fully light-adapted state regardless of the time of day. The higher amplitudes and reduced circadian regulation of the b-wave of HRGPcreGjd2fl/fl mice may be due to increased synaptic strength at the cone to ON bipolar cell synapse due to electrotonic isolation of the terminals lacking gap junctions.


Asunto(s)
Adaptación Ocular/fisiología , Ritmo Circadiano/fisiología , Conexinas/metabolismo , Adaptación a la Oscuridad/fisiología , Electrorretinografía/métodos , Células Fotorreceptoras Retinianas Conos/metabolismo , Animales , Uniones Comunicantes , Ratones , Ratones Transgénicos , Modelos Animales , Proteína delta-6 de Union Comunicante
8.
Bioorg Med Chem ; 17(17): 6463-80, 2009 Sep 01.
Artículo en Inglés | MEDLINE | ID: mdl-19648014

RESUMEN

The synthesis and structure-activity relationship analysis of a novel class of amide-based biaryl NR2B-selective NMDA receptor antagonists are presented. Some of the studied compounds are potent, selective, non-competitive, and voltage-independent antagonists of NR2B-containing NMDA receptors. Like the founding member of this class of antagonists (ifenprodil), several interesting compounds of the series bind to the amino terminal domain of the NR2B subunit to inhibit function. Analogue potency is modulated by linker length, flexibility, and hydrogen bonding opportunities. However, unlike previously described classes of NR2B-selective NMDA antagonists that exhibit off-target activity at a variety of monoamine receptors, the compounds described herein show much diminished effects against the hERG channel and alpha(1)-adrenergic receptors. Selections of the compounds discussed have acceptable half-lives in vivo and are predicted to permeate the blood-brain barrier. These data together suggest that masking charged atoms on the linker region of NR2B-selective antagonists can decrease undesirable side effects while still maintaining on-target potency.


Asunto(s)
Amidas/síntesis química , Fármacos Neuroprotectores/síntesis química , Receptores de N-Metil-D-Aspartato/antagonistas & inhibidores , Sitio Alostérico , Amidas/química , Amidas/farmacología , Animales , Línea Celular , Perros , Canales de Potasio Éter-A-Go-Go/metabolismo , Humanos , Fármacos Neuroprotectores/química , Fármacos Neuroprotectores/farmacología , Oocitos/metabolismo , Receptores de N-Metil-D-Aspartato/metabolismo , Relación Estructura-Actividad , Xenopus laevis
9.
J Neurotrauma ; 35(1): 118-129, 2018 01 01.
Artículo en Inglés | MEDLINE | ID: mdl-28599600

RESUMEN

Ocular blast injury is a major medical concern for soldiers and explosion victims due to poor visual outcomes. To define the changes in gene expression following a blast injury to the eye, we examined retinal ribonucleic acid (RNA) expression in 54 mouse strains 5 days after a single 50-psi overpressure air wave blast injury. We observe that almost 40% of genes are differentially expressed with a false discovery rate (FDR) of <0.001, even though the nominal changes in RNA expression are rather small. Moreover, we find through machine learning approaches that genetic networks related to the innate and acquired immune system are activated. Accompanied by lymphocyte invasion into the inner retina, blast injury also results in progressive loss of visual function and retinal ganglion cells (RGCs). Collectively, these data demonstrate how systems genetics can be used to put meaning to the transcriptome changes following ocular blast injury that eventually lead to blindness.


Asunto(s)
Traumatismos por Explosión/genética , Traumatismos por Explosión/inmunología , Lesiones Oculares/patología , Retina/patología , Transcripción Genética , Animales , Traumatismos por Explosión/patología , Lesiones Oculares/inmunología , Expresión Génica/inmunología , Redes Reguladoras de Genes/inmunología , Ratones , Retina/inmunología , Transcripción Genética/inmunología
10.
J Neurosci ; 25(17): 4319-29, 2005 Apr 27.
Artículo en Inglés | MEDLINE | ID: mdl-15858058

RESUMEN

We have studied the involvement of the thrombin receptor [protease-activated receptor-1 (PAR-1)] in astrogliosis, because extravasation of PAR-1 activators, such as thrombin, into brain parenchyma can occur after blood-brain barrier breakdown in a number of CNS disorders. PAR1-/- animals show a reduced astrocytic response to cortical stab wound, suggesting that PAR-1 activation plays a key role in astrogliosis associated with glial scar formation after brain injury. This interpretation is supported by the finding that the selective activation of PAR-1 in vivo induces astrogliosis. The mechanisms by which PAR-1 stimulates glial proliferation appear to be related to the ability of PAR-1 receptor signaling to induce sustained extracellular receptor kinase (ERK) activation. In contrast to the transient activation of ERK by cytokines and growth factors, PAR-1 stimulation induces a sustained ERK activation through its coupling to multiple G-protein-linked signaling pathways, including Rho kinase. This sustained ERK activation appears to regulate astrocytic cyclin D1 levels and astrocyte proliferation in vitro and in vivo. We propose that this PAR-1-mediated mechanism underlying astrocyte proliferation will operate whenever there is sufficient injury-induced blood-brain barrier breakdown to allow extravasation of PAR-1 activators.


Asunto(s)
Astrocitos/patología , Lesiones Encefálicas/patología , Gliosis/etiología , Receptor PAR-1/metabolismo , Amidas/farmacología , Análisis de Varianza , Animales , Animales Recién Nacidos , Northern Blotting/métodos , Western Blotting/métodos , Lesiones Encefálicas/fisiopatología , Bromodesoxiuridina/metabolismo , Butadienos/farmacología , Recuento de Células/métodos , Movimiento Celular/fisiología , Proliferación Celular , Células Cultivadas , Técnicas de Cocultivo/métodos , Colforsina/farmacología , Ciclina D1/metabolismo , Modelos Animales de Enfermedad , Interacciones Farmacológicas , Inhibidores Enzimáticos/farmacología , Lateralidad Funcional , Proteína Ácida Fibrilar de la Glía/metabolismo , Inmunohistoquímica/métodos , Quinasas Quinasa Quinasa PAM/metabolismo , Masculino , Ratones , Ratones Noqueados , Microglía/patología , Nitrilos/farmacología , Oligopéptidos/farmacología , Piridinas/farmacología , ARN Mensajero/biosíntesis , Receptor PAR-1/deficiencia , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa/métodos , Trombina/farmacología , Factores de Tiempo
11.
Neuron ; 85(6): 1305-1318, 2015 Mar 18.
Artículo en Inglés | MEDLINE | ID: mdl-25728572

RESUMEN

Stroke remains a significant problem despite decades of work on neuroprotective strategies. NMDA receptor (NMDAR) antagonists are neuroprotective in preclinical models, but have been clinically unsuccessful, in part due to side effects. Here we describe a prototypical GluN2B-selective antagonist with an IC50 value that is 10-fold more potent at acidic pH 6.9 associated with ischemic tissue compared to pH 7.6, a value close to the pH in healthy brain tissue. This should maximize neuroprotection in ischemic tissue while minimizing on-target side effects associated with NMDAR blockade in noninjured brain regions. We have determined the mechanism underlying pH-dependent inhibition and demonstrate the utility of this approach in vivo. We also identify dicarboxylate dimers as a novel proton sensor in proteins. These results provide insight into the molecular basis of pH-dependent neuroprotective NMDAR block, which could be beneficial in a wide range of neurological insults associated with tissue acidification.


Asunto(s)
Concentración de Iones de Hidrógeno , Fármacos Neuroprotectores/farmacología , Receptores de N-Metil-D-Aspartato/metabolismo , Animales , Encéfalo/efectos de los fármacos , Encéfalo/metabolismo , Modelos Animales de Enfermedad , Humanos , Concentración de Iones de Hidrógeno/efectos de los fármacos , Masculino , Ratones Endogámicos C57BL , Fármacos Neuroprotectores/toxicidad , Receptores de N-Metil-D-Aspartato/antagonistas & inhibidores , Receptores de N-Metil-D-Aspartato/química , Accidente Cerebrovascular/tratamiento farmacológico , Accidente Cerebrovascular/metabolismo
12.
J Cereb Blood Flow Metab ; 24(9): 964-71, 2004 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-15356417

RESUMEN

Cardiovascular and neurologic surgeries often involve a temporary reduction in cerebral blood flow. In these conditions, as well as during cerebral ischemia and traumatic brain injury, the temporary loss of oxygen and glucose initiates a cascade of cellular events that culminate in neuronal death and damage. Understanding the mechanisms that contribute to neuronal death after hypoxia/ischemia is critically important for treatment of such brain injury. Here, we use a model of combined cerebral hypoxia/ischemia (H/I) to examine the role of protease-activated receptor-1 (PAR-1) in hypoxic/ischemic neuronal damage. Our data show that PAR-1-deficient mice have smaller lesion volumes than wild-type controls after 45 minutes of H/I. The results of the genetic block of PAR-1 were corroborated using a PAR-1 antagonist, which decreased infarct volume in wild-type C57Bl6 mice. Examination of cellular responses to H/I reveals that PAR-1 -/- animals have less cellular death and diminished glial fibrillary acidic protein expression. Additionally, PAR-1 -/- mice exhibit less motor behavior impairment in rotorod and inverted wire-hang tests. These data suggest that PAR-1 contributes to hypoxic/ischemic brain injury and are consistent with other studies that implicate serine proteases and their receptors in neuropathology after cerebral insults.


Asunto(s)
Encéfalo/patología , Hipoxia-Isquemia Encefálica/fisiopatología , Degeneración Nerviosa/patología , Neuronas/patología , Receptor PAR-1/deficiencia , Animales , Muerte Celular/fisiología , Lateralidad Funcional , Proteína Ácida Fibrilar de la Glía/metabolismo , Procesamiento de Imagen Asistido por Computador , Inmunohistoquímica , Masculino , Ratones
13.
Exp Neurol ; 217(1): 136-46, 2009 May.
Artículo en Inglés | MEDLINE | ID: mdl-19416668

RESUMEN

Protease-activated receptor 1 (PAR1) is a G-protein coupled receptor that is expressed throughout the central nervous system. PAR1 activation by brain-derived as well as blood-derived proteases has been shown to have variable and complex effects in a variety of animal models of neuronal injury and inflammation. In this study, we have evaluated the effects of PAR1 on lesion volume in wild-type or PAR1-/- C57Bl/6 mice subjected to transient occlusion of the middle cerebral artery or injected with NMDA in the striatum. We found that removal of PAR1 reduced infarct volume following transient focal ischemia to 57% of control. Removal of PAR1 or application of a PAR1 antagonist also reduced the neuronal injury associated with intrastriatal injection of NMDA to 60% of control. To explore whether NMDA receptor potentiation by PAR1 activation contributes to the harmful effects of PAR1, we investigated the effect of NMDA receptor antagonists on the neuroprotective phenotype of PAR1-/- mice. We found that MK801 reduced penumbral but not core neuronal injury in mice subjected to transient middle cerebral artery occlusion or intrastriatal NMDA injection. Lesion volumes in both models were not significantly different between PAR1-/- mice treated with and without MK801. Use of the NMDA receptor antagonist and dissociative anesthetic ketamine also renders NMDA-induced lesion volumes identical in PAR1-/- mice and wild-type mice. These data suggest that the ability of PAR1 activation to potentiate NMDA receptor function may underlie its harmful actions during injury.


Asunto(s)
Lesiones Encefálicas/prevención & control , Neuronas/fisiología , Receptor PAR-1/fisiología , Receptores de N-Metil-D-Aspartato/fisiología , Análisis de Varianza , Animales , Lesiones Encefálicas/genética , Lesiones Encefálicas/metabolismo , Lesiones Encefálicas/patología , Células Cultivadas , Cuerpo Estriado/citología , Cuerpo Estriado/efectos de los fármacos , Cuerpo Estriado/metabolismo , Modelos Animales de Enfermedad , Maleato de Dizocilpina/farmacología , Embrión de Mamíferos , Agonistas de Aminoácidos Excitadores/farmacología , Agonistas de Aminoácidos Excitadores/uso terapéutico , Antagonistas de Aminoácidos Excitadores/farmacología , Femenino , Guanidinas/farmacología , Inyecciones Intraventriculares/métodos , Ataque Isquémico Transitorio/genética , Ataque Isquémico Transitorio/prevención & control , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , N-Metilaspartato/farmacología , N-Metilaspartato/uso terapéutico , Neuronas/efectos de los fármacos , Oligopéptidos/farmacología , Embarazo , Ratas , Receptor PAR-1/antagonistas & inhibidores , Receptor PAR-1/deficiencia , Receptor PAR-1/metabolismo
14.
J Med Chem ; 51(18): 5506-21, 2008 Sep 25.
Artículo en Inglés | MEDLINE | ID: mdl-18800760

RESUMEN

Enantiomeric propanolamines have been identified as a new class of NR2B-selective NMDA receptor antagonists. The most effective agents are biaryl structures, synthesized in six steps with overall yields ranging from 11-64%. The compounds are potent and selective inhibitors of NR2B-containing recombinant NMDA receptors with IC 50 values between 30-100 nM. Potency is strongly controlled by substitution on both rings and the centrally located amine nitrogen. SAR analysis suggests that well-balanced polarity and chain-length factors provide the greatest inhibitory potency. Structural comparisons based on 3D shape analysis and electrostatic complementarity support this conclusion. The antagonists are neuroprotective in both in vitro and in vivo models of ischemic cell death. In addition, some compounds exhibit anticonvulsant properties. Unlike earlier generation NMDA receptor antagonists and some NR2B-selective antagonists, the present series of propanolamines does not cause increased locomotion in rodents. Thus, the NR2B-selective antagonists exhibit a range of therapeutically interesting properties.


Asunto(s)
Antagonistas de Aminoácidos Excitadores/farmacología , Propanolaminas/farmacología , Receptores de N-Metil-D-Aspartato/antagonistas & inhibidores , Animales , Anticonvulsivantes/farmacología , Barrera Hematoencefálica , Encéfalo/metabolismo , Antagonistas de Aminoácidos Excitadores/sangre , Antagonistas de Aminoácidos Excitadores/química , Antagonistas de Aminoácidos Excitadores/farmacocinética , Espectroscopía de Resonancia Magnética , Espectrometría de Masas , Actividad Motora/efectos de los fármacos , Propanolaminas/sangre , Propanolaminas/química , Propanolaminas/farmacocinética , Ratas , Estereoisomerismo , Relación Estructura-Actividad , Xenopus
15.
Neurobiol Learn Mem ; 88(3): 295-304, 2007 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-17544303

RESUMEN

The roles of serine proteases and protease activated receptors have been extensively studied in coagulation, wound healing, inflammation, and neurodegeneration. More recently, serine proteases have been suggested to influence synaptic plasticity. In this context, we examined the role of protease activated receptor 1 (PAR1), which is activated following proteolytic cleavage by thrombin and plasmin, in emotionally motivated learning. We were particularly interested in PAR1 because its activation enhances the function of NMDA receptors, which are required for some forms of synaptic plasticity. We examined several baseline behavioral measures, including locomotor activity, expression of anxiety-like behavior, motor task acquisition, nociceptive responses, and startle responses in C57Bl/6 mice in which the PAR1 receptor has been genetically deleted. In addition, we evaluated learning and memory in these mice using two memory tasks, passive avoidance and cued fear-conditioning. Whereas locomotion, pain response, startle, and measures of baseline anxiety were largely unaffected by PAR1 removal, PAR1-/- animals showed significant deficits in a passive avoidance task and in cued fear conditioning. These data suggest that PAR1 may play an important role in emotionally motivated learning.


Asunto(s)
Aprendizaje por Asociación/fisiología , Reacción de Prevención/fisiología , Condicionamiento Clásico/fisiología , Receptor PAR-1/metabolismo , Retención en Psicología/fisiología , Animales , Señales (Psicología) , Miedo/fisiología , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Actividad Motora/fisiología , Destreza Motora/fisiología , Receptor PAR-1/genética , Reflejo de Sobresalto/fisiología
16.
Mol Pharmacol ; 72(4): 907-20, 2007 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-17622578

RESUMEN

The four N-methyl-d-aspartate (NMDA) receptor NR2 subunits (NR2A-D) have different developmental, anatomical, and functional profiles that allow them to serve different roles in normal and neuropathological situations. Identification of subunit-selective NMDA receptor agonists, antagonists, or modulators could prove to be both valuable pharmacological tools as well as potential new therapeutic agents. We evaluated the potency and efficacy of a wide range of glutamate-like compounds at NR1/NR2A, NR1/NR2B, NR1/NR2C, and NR1/NR2D receptors. Twenty-five of 53 compounds examined exhibited agonist activity at the glutamate binding site of NMDA receptors. Concentration-response relationships were determined for these agonists at each NR2 subunit. We find consistently higher potency at the NR2D subunit for a wide range of dissimilar structures, with (2S,4R)-4-methylglutamate (SYM2081) showing the greatest differential potency between NR2A- and NR2D-containing receptors (46-fold). Analysis of chimeric NR2A/D receptors suggests that enhanced agonist potency for NR2D is controlled by residues in both of the domains (Domain1 and Domain2) that compose the bilobed agonist binding domain. Molecular dynamics (MD) simulations comparing a crystallography-based hydrated NR1/NR2A model with a homology-based NR1/NR2D hydrated model of the agonist binding domains suggest that glutamate exhibits a different binding mode in NR2D compared with NR2A that accommodates a 4-methyl substitution in SYM2081. Mutagenesis of functionally divergent residues supports the conclusions drawn based on the modeling studies. Despite high homology and conserved atomic contact residues within the agonist binding pocket of NR2A and NR2D, glutamate adopts a different binding orientation that could be exploited for the development of subunit selective agonists and competitive antagonists.


Asunto(s)
Agonistas de Aminoácidos Excitadores/farmacología , Receptores de N-Metil-D-Aspartato/agonistas , Animales , Sitios de Unión , Cristalografía por Rayos X , Relación Dosis-Respuesta a Droga , Modelos Moleculares , Mutagénesis Sitio-Dirigida , Técnicas de Placa-Clamp , Conformación Proteica , Ratas , Receptores de N-Metil-D-Aspartato/química , Receptores de N-Metil-D-Aspartato/genética , Proteínas Recombinantes/agonistas , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Xenopus laevis
17.
J Physiol ; 581(Pt 1): 107-28, 2007 May 15.
Artículo en Inglés | MEDLINE | ID: mdl-17303642

RESUMEN

We have compared the potencies of structurally distinct channel blockers at recombinant NR1/NR2A, NR1/NR2B, NR1/NR2C and NR1/NR2D receptors. The IC50 values varied with stereochemistry and subunit composition, suggesting that it may be possible to design subunit-selective channel blockers. For dizocilpine (MK-801), the differential potency of MK-801 stereoisomers determined at recombinant NMDA receptors was confirmed at native receptors in vitro and in vivo. Since the proton sensor is tightly linked both structurally and functionally to channel gating, we examined whether blocking molecules that interact in the channel pore with the gating machinery can differentially sense protonation of the receptor. Blockers capable of remaining trapped in the pore during agonist unbinding showed the strongest dependence on extracellular pH, appearing more potent at acidic pH values that promote channel closure. Determination of pK(a) values for channel blockers suggests that the ionization of ketamine but not of other blockers can influence its pH-dependent potency. Kinetic modelling and single channel studies suggest that the pH-dependent block of NR1/NR2A by (-)MK-801 but not (+)MK-801 reflects an increase in the MK-801 association rate even though protons reduce channel open probability and thus MK-801 access to its binding site. Allosteric modulators that alter pH sensitivity alter the potency of MK-801, supporting the interpretation that the pH sensitivity of MK-801 binding reflects the changes at the proton sensor rather than a secondary effect of pH. These data suggest a tight coupling between the proton sensor and the ion channel gate as well as unique subunit-specific mechanisms of channel block.


Asunto(s)
Canales Iónicos/antagonistas & inhibidores , Protones , Receptores de N-Metil-D-Aspartato/antagonistas & inhibidores , Animales , Línea Celular , Maleato de Dizocilpina/farmacología , Electrofisiología , Antagonistas de Aminoácidos Excitadores/farmacología , Humanos , Concentración de Iones de Hidrógeno , Activación del Canal Iónico , Canales Iónicos/efectos de los fármacos , Canales Iónicos/fisiología , Masculino , Ratones , Ratones Endogámicos C57BL , Técnicas de Placa-Clamp , Ratas , Ratas Sprague-Dawley , Receptores de N-Metil-D-Aspartato/efectos de los fármacos , Receptores de N-Metil-D-Aspartato/fisiología , Proteínas Recombinantes/antagonistas & inhibidores , Estereoisomerismo , Xenopus laevis
18.
Mol Pharmacol ; 63(6): 1212-22, 2003 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-12761330

RESUMEN

Extracellular protons inhibit N-methyl-D-aspartate (NMDA) receptors with an IC50 value in the physiological pH range. To identify the molecular determinants of proton sensitivity, we used scanning mutagenesis of the NR1 subunit to search for residues that control proton inhibition of NMDA receptors. Homology modeling of the extracellular domains suggested that residues at which mutations perturbed pH sensitivity were localized in discrete regions. The majority of mutations that strongly affected proton sensitivity were clustered in the extracellular end of the second transmembrane domain (M3) and adjacent linker leading to the S2 portion of the glycine-binding domain of NR1. Mutations in NR2A confirmed that the analogous region controls the pH sensitivity of this subunit and also identified the linker region between the third transmembrane domain (M4) and the S2 portion of the NR2 glutamate binding domain as an additional determinant of proton sensitivity. One mutant receptor, NR1(A649C)/NR2A(A651T), showed a 145-fold reduction in the IC50 for protons (IC50, 17.3 microM corresponding to pH 4.9). The M3-S2 linker region has been suggested to control NMDA receptor gating, leading to the hypothesis that the proton sensor and receptor gate may be structurally and functionally integrated.


Asunto(s)
N-Metilaspartato/metabolismo , Subunidades de Proteína/metabolismo , Protones , Receptores de N-Metil-D-Aspartato/metabolismo , Secuencia de Aminoácidos , Animales , Concentración de Iones de Hidrógeno , Modelos Moleculares , Datos de Secuencia Molecular , Mutación , Oocitos/metabolismo , Subunidades de Proteína/genética , Receptores de N-Metil-D-Aspartato/genética , Homología de Secuencia de Aminoácido , Xenopus laevis
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