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Ausencia de conductividad de potasio en los axones mielinizados centrales

J D Kocsis, S G Waxman

|September 25, 1980

Resumen

Las conductancias de potasio (gk) se enmascaran en los axones mielinados periféricos de mamíferos, apareciendo solo después de la ruptura de la mielina. Los axones mielinados centrales, al igual que los axones de la columna dorsal, no muestran gk detectable, lo que sugiere mecanismos únicos de repolarización.

Área de la Ciencia:

La neurociencia es la neurociencia.
Electrofisiología Celular Electrofisiología celular
Fisiología Axonal Fisiología Axonal

Sus antecedentes:

El potencial de acción depende de los cambios en la permeabilidad de los iones sodio y potasio dependientes del voltaje.
Se cree que las conductancias de potasio (gk) son mínimas en los axones mielinizados periféricos de mamíferos intactos.
La repolarización en estas fibras se ha atribuido a la inactivación del sodio y a las corrientes de fuga.

Objetivo del estudio:

Para investigar la presencia y el papel de los canales de potasio en los axones mielinizados centrales.
Para determinar si las conductancias de potasio están enmascaradas en los axones mielinizados centrales, similares a los axones periféricos.

Principales métodos:

Experimentos con pinzas de tensión en axones mielinizados centrales de mamíferos (axones de la columna dorsal).
Evaluación de las conductancias de potasio (gk) en preparaciones axonales intactas y potencialmente desmielinizadas.
Comparación con los hallazgos de los axones mielinados periféricos.

Principales resultados:

Las conductancias de potasio (gk) no fueron detectables en los axones de la columna dorsal de los mamíferos.
Los axones mielinados periféricos exhiben un GK prominente en la ruptura aguda de la mielina, lo que sugiere canales enmascarados.
La desmielinización desenmascara el gk en los axones periféricos, que pueden ser bloqueados por los inhibidores del gk.

Conclusiones:

Los axones mielinizados centrales de los mamíferos (columna dorsal) carecen de conductancias de potasio detectables.
Los canales de potasio pueden estar presentes pero enmascarados bajo la mielina en los axones periféricos.
Es probable que los axones mielinados centrales utilicen diferentes mecanismos para la repolarización del potencial de acción que los axones periféricos.

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