903 resultados para Raymond Aron


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Using immunocytochemistry and multiunit recording of afferent activity of the whole vestibular nerve, we investigated the role of metabotropic glutamate receptors (mGluR) in the afferent neurotransmission in the frog semicircular canals (SCC). Group I (mGluR1alpha) and group II (mGluR2/3) mGluR immunoreactivities were distributed to the vestibular ganglion neurons, and this can be attributed to a postsynaptic locus of metabotropic regulation of rapid excitatory transmission. The effects of group I/II mGluR agonist (1S,3R)-1-aminocyclopentane-trans-1,3-dicarboxylic acid (ACPD) and antagonist (R,S)-alpha-methyl-4-carboxyphenylglycine (MCPG) on resting and chemically induced afferent activity were studied. ACPD (10-100 microM) enhanced the resting discharge frequency. MCPG (5-100 microM) led to a concentration-dependent decrease of both resting activity and ACPD-induced responses. If the discharge frequency had previously been restored by L-glutamate (L-Glu) in high-Mg2+ solution, ACPD elicited a transient increase in the firing rate in the afferent nerve suggesting that ACPD acts on postsynaptic receptors. The L-Glu agonists, alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA) and N-methyl-D-aspartate (NMDA), were tested during application of ACPD. AMPA- and NMDA-induced responses were higher in the presence than absence of ACPD, implicating mGluR in the modulation of ionotropic glutamate receptors. These results indicate that activation of mGluR potentiates AMPA and NMDA responses through a postsynaptic interaction. We conclude that ACPD may exert modulating postsynaptic effects on vestibular afferents and that this process is activity-dependent.

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Référence bibliographique : Rol, 56950

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Référence bibliographique : Rol, 57784

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La población femenina y la indígena del Ecuador han presentado continuamente desigualdades de ingresos respecto a la población masculina y a la no indígena, respectivamente. El presente trabajo reporta que una parte de las diferencias salariales a favor de los hombres y de la población no indígena es resultado de la discriminación salarial por razones de género y etnia. Este resultado se ha obtenido estimando ecuaciones mincerianas de ingresos corrigiendo el problema de se sgo de selección muestral y utilizando la metodología de descomposición de las brechas salariales de Oaxaca (1973) y Newmak (1988) también corregidas por el problema de sesgo de selección muestral.

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Référence bibliographique : Rol, 57636

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Référence bibliographique : Rol, 57786

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Référence bibliographique : Rol, 57778

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Référence bibliographique : Rol, 57779