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La liberación rápida de neurotransmisores desencadenada por la afluencia de Ca a través de los receptores de
Andrés E Chávez1, Joshua H Singer, Jeffrey S Diamond
1Synaptic Physiology Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892-3701, USA.
Nature
|October 13, 2006
Resumen
La inhibición de la retroalimentación en la retina se basa en un nuevo mecanismo. La liberación de GABA de las células amacrinas A17 es desencadenada por los receptores AMPA permeables al calcio, no por los canales de calcio controlados por voltaje, revelando una nueva vía de circuito neuronal.
Área de la Ciencia:
- La neurociencia es la neurociencia.
- Fisiología de la retina Fisiología de la retina
- La transmisión sináptica es la transmisión sináptica.
Sus antecedentes:
- Las sinapsis recíprocas entre las células amacrinas A17 y las células bipolares de varilla (RBC) son cruciales para las respuestas evocadas por la luz retiniana.
- La inhibición de la retroalimentación mediada por el GABA (ácido gamma-aminobutírico) de las células A17 a los glóbulos rojos da forma al procesamiento visual.
- Los mecanismos precisos que rigen la liberación de GABA de las dendritas de las células A17 permanecieron indeterminados.
Objetivo del estudio:
- Para dilucidar los mecanismos moleculares que controlan la liberación de GABA de las células amacrinas A17.
- Para investigar si los canales de calcio activados por voltaje (VGCCs) median la liberación de GABA en estas sinapsis.
- Para identificar la fuente de calcio y las vías de señalización involucradas en la inhibición de la retroalimentación.
Principales métodos:
- Registros electrofisiológicos en rebanadas de retina de rata.
- Manipulación farmacológica de receptores y canales iónicos.
- Técnicas de imagen del calcio para monitorear la dinámica intracelular del calcio.
Principales resultados:
- La liberación de GABA de las células A17 es independiente de los VGCC y la despolarización de la membrana.
- El influjo de calcio a través de los receptores AMPA permeables al calcio (AMPARs) desencadena la liberación de GABA.
- La señalización del calcio mediada por AMPAR se amplifica mediante la liberación de calcio inducida por el calcio (CICR) de las reservas internas.
Conclusiones:
- Una nueva forma de transmisión sináptica rápida, independiente de los VGCC, opera en la retina.
- Los AMPAR y CICR permeables al calcio son esenciales para la inhibición de la retroalimentación en el circuito amacrino A17 y el RBC.
- Este descubrimiento revela un mecanismo no reconocido previamente para regular la actividad del circuito neuronal en la retina.
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