La neurotransmisión gabaérgica durante el desarrollo del sistema nervioso central
Mariano José
Mariano José Scolari, Dra. Gabriela Beatriz Acosta Conclusiones Tras esta reseña y de acuerdo con una gran cantidad de trabajos de investigación documentados, se demuestra que el cerebro es un sistema dinámico desde el primer día de vida. Las gráficas que aquí se exponen dejan un ejemplo certero de ello. Lo intrigante de la maduración del SNC, es que mientras ella está ocurriendo, las moléculas que componen un mismo sistema de neurotransmisión, en este caso el GABAérgico, muestran perfiles de expresión completamente diferentes (14, 31). Si se considera el perfil de expresión de la subunidad α 1 del receptor GABA A y la del transportador de GABA: el GAT-3, se observa que ambas proteínas incrementan sus niveles de expresión desde el PD 0 hasta un pico máximo, que se encuentra en el PD 30 para la subunidad α 1 y aproximadamente en el PD 20 para el transportador. Algo similar ocurre si se compara el perfil de expresión del GAT-3 con el de las subunidades α 2 y α 3 (Figuras 4 y 6) (14, 31). Sin embargo, si se tiene en cuenta la expresión del GAT-1 y de las subunidades mencionadas, se observa que su perfil de expresión no es análogo, como sucede con el GAT-3, sino que la expresión del GAT-1 decrece desde niveles elevados de manera casi constante hasta el PD 20 (Figura 3) (14). Esto sugiere que durante las primeras etapas del desarrollo postnatal, son las subunidades α 1-3 y el GAT-3 los principales mediadores de la neurotransmisión GABAérgica y que el intervalo comprendido entre el PD 20 y el PD 30 es clave para el desarrollo del cerebro. Otro período importante en el desarrollo son las dos primeras semanas postnatales, momento en donde ocurre el “switch” del GABA de excitatorio a inhibitorio (7). Este fenómeno determina la funcionalidad del GABA como neurotransmisor en el cerebro adulto, aunque en algunas neuronas centrales, sobre todo en sus conos axónicos, se observan fenómenos excitatorios mediados por el GABA (31). En conclusión, la formación del sistema GABAérgico cortical es un proceso altamente dinámico en el que participan múltiples proteínas, cada una con una función esencial y específica que la hace única en el desarrollo del SNC. Referencias Bibliográficas 1. Conti F, Minelli A, Melone M. GABA transporters in the mammalian cerebral cortex: localization, development and pathological implications. Brain Res Brain Res Rev 2004;45(3):196-212. 2. Krnjevic K. Neurotransmitters in Cerebral Cortex: a general account. En: E.G. Jones, A. Peters (Eds.). Cerebral Cortex, Functional Properties of Cortical Cells, vol. 2. Plenum, New York; 1984. pp. 39–61. 3. 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