RESUMEN
In order to investigate the involvement of mGlu1 and mGlu5 metabotropic glutamate receptors in the development of postischemic neuronal death, we examined the effects of selective agonists and antagonists in models of cerebral ischemia in vitro and in vivo. In murine cortical cell cultures and rat organotypic hippocampal slices exposed to oxygen and glucose deprivation (OGD), the mGlu1 antagonists 1-aminoindan-1,5-dicarboxylic acid (AIDA; 300 microM), (S)-(+)-2-(3'-carboxybicyclo[1.1.1]pentyl)-glycine (CBPG; 300 microM), 7-hydroxyiminocyclopropan[b]chromen-1a-carboxylic acid ethyl ester (CPCCOEt; 10-30 microM) and (+)-2-methyl-4-carboxyphenylglycine (LY367385; 30-100 microM) reduced neuronal loss when added to the medium during OGD and the subsequent 24-h recovery period. On the contrary, the potent and selective mGlu5 antagonist methyl-6-(phenylethynyl)-pyridine (MPEP; 0.1-1 microM) did not exhibit neuroprotection in any of these in vitro models. Incubation with the nonselective mGlu1 and mGlu5 agonist 3,5-dihydroxyphenylglycine (3,5-DHPG; 300 microM) but not with the mGlu5 agonist (RS)-2-chloro-5-hydroxyphenylglycine (CHPG; 1 mM) enhanced the severity of OGD-induced neuronal damage. In gerbils subjected to global ischemia, intracerebroventricular administration of AIDA (100 nmol two times) or CBPG (300 nmol, two times) afforded consistent protection against CA1 pyramidal cell death, whereas MPEP (10 pmol i.c.v two times and 10 mg/kg i.p two times) failed to reduce postischemic hippocampal damage. Our results suggest that activation of mGlu1 but not mGlu5 receptor contributes to postischemic neuronal injury.
Asunto(s)
Isquemia Encefálica/patología , Agonistas de Aminoácidos Excitadores/farmacología , Glicina/análogos & derivados , Neuronas/patología , Receptores de Glutamato Metabotrópico/agonistas , Animales , Compuestos Bicíclicos con Puentes/farmacología , Línea Celular , Cricetinae , Antagonistas de Aminoácidos Excitadores/farmacología , Gerbillinae , Glucosa/deficiencia , Glucosa/fisiología , Glicina/farmacología , Hipocampo/efectos de los fármacos , Hipocampo/metabolismo , Indanos/farmacología , Ataque Isquémico Transitorio/patología , Riñón/efectos de los fármacos , Riñón/metabolismo , Fármacos Neuroprotectores/farmacología , Técnicas de Cultivo de Órganos , Consumo de Oxígeno/efectos de los fármacos , Fosfatidilinositoles/metabolismo , Receptor del Glutamato Metabotropico 5 , Receptores de Glutamato Metabotrópico/antagonistas & inhibidores , Fosfolipasas de Tipo C/metabolismoRESUMEN
We examined the pharmacological properties of 3-methyl-aminothiophene dicarboxylic acid (3-MATIDA) by measuring second messenger responses in baby hamster kidney cells stably transfected with mGlu1a, mGlu2, mGlu4a or mGlu5a receptors and ionotropic glutamate receptor agonist-induced depolarizations in mouse cortical wedges. 3-MATIDA was a potent (IC(50)=6.3 microM, 95% confidence limits 3-15) and relatively selective mGlu1 receptor antagonist. When tested on mGlu2, mGlu4 or mGlu5 receptors its IC(50) was >300 microM. When tested in cortical wedges, however, 3-MATIDA was also able to antagonize AMPA or NMDA responses with an IC(50) of 250 microM. When present in the incubation medium of cultured murine cortical cells, 3-MATIDA (1-100 microM) significantly reduced the death of neurons induced by 60 min of oxygen and glucose deprivation (OGD), even when added up to 60 min after OGD. A similar neuroprotective activity was observed when 3-MATIDA was present at 10-100 microM in the medium of rat organotypic hippocampal slice cultures exposed to 30 min OGD. Systemic administration of 3-MATIDA (3-10 mg/kg, immediately and 1 h after the onset of ischemia) reduced the volume of brain infarcts following permanent middle cerebral artery occlusion in rats. Our results show that 3-MATIDA is a potent and possibly selective mGlu 1 receptor antagonist that may be considered as a novel prototype neuroprotective agent.