Name: synaptic pruning in long-term depression
Uploaded: 2019-03-11T09:21:27.000Z
Duration: 1 min 5 s
Channel: JoVE

- [Presentador] La depresión
a largo plazo, o DLP,

es un proceso de debilitamiento
sináptico que ocurre

a través del tiempo

entre las conexiones
neuronales presinápticas

y postsinápticas.

Un mecánismo a través
del cual ocurre la DLP

depende de la cantidad de iones de calcio

circulando hacia la neurona postsináptica

después de una estimulación presináptica.

La concentración baja de calcio debida a

la infrecuente estimulación presináptica

puede iniciar una cascada de señales

que culmina en la endocitosis

o el desprendimiento de los
receptores de glutamato AMPA

de la membrana.

Como resultado, la respuesta postsináptica

a la misma estimulación
presináptica esporádica

se ve adicionalmente debilitada.

Así, la DLP es importante para aprender,

ya que las sinapsis no
empleadas o raramente empleadas

son debilitadas y pueden
incluso ser eliminadas,

liberando así recursos y espacio

que pueden ser usado por la
neurona para otras funciones,

tales como el fortalecimiento de LTP de

sinapsis más importantes.

Kukushkin, Nikolay Vadimovich y Thomas James Carew. "La memoria lleva tiempo". Neurona 95, n.º 2 (19 de julio de 2017): 259–79. [<a href="https://doi.org/10.1016/j.neuron.2017.05.029" target="__blank">Fuente</a>]

Lüscher, Christian y Robert C. Malenka. "Potenciación a largo plazo dependiente del receptor NMDA y depresión a largo plazo (LTP/LTD)". Cold Spring Harbor Perspectives in Biology 4, no. 6 (1 de junio de 2012): a005710. [<a href="https://doi.org/10.1101/cshperspect.a005710" target="__blank">Fuente</a>]

depresión a largo plazo

La depresión a largo plazo, o LTD, es una de las formas en que la plasticidad sináptica,cambios en la fuerza de las sinapsis químicas,puede ocurrir en el cerebro. LTD es el proceso de debilitamiento sináptico que ocurre con el tiempo entre las conexiones neuronales pre y postsinápticas. El debilitamiento sináptico de LTD actúa en oposición al fortalecimiento sináptico mediante potenciación a largo plazo (LTP) y juntos son los principales mecanismos que subyacen al aprendizaje y la memoria. <h4>Mecanismo de concentración de iones de calcio</h4> Si con el tiempo todas las sinapsis se fortalecen al máximo mediante LTP o algún otro mecanismo, la eficiencia del cerebro se estabilizaría, lo que dificultaría el aprendizaje y la formación de nuevos recuerdos. LTD es una forma de podar las sinapsis más débiles, liberando así recursos y devolviendo flexibilidad al sistema nervioso central. Un mecanismo por el cual se produce LTD depende de la cantidad de iones de calcio en la neurona postsináptica después de la estimulación presináptica. Los niveles bajos o poco frecuentes de estimulación presináptica conducen a una baja afluencia de iones de calcio y, en consecuencia, a una baja concentración de iones de calcio en la neurona postsináptica. La baja concentración de iones calcio inicia una cascada de señalización que culmina en la endocitosis o eliminación de los receptores de glutamato del ácido α-amino-3-hidroxi-5-metil-4-isoxazolpropiónico (AMPA) de la membrana plasmática. Como resultado, la respuesta postsináptica a la misma estimulación presináptica esporádica se debilita aún más, ya que hay menos canales para que los iones cargados positivamente entren y despolaricen la membrana. La neurona reutiliza los receptores AMPA posteriormente y/o los separa en sus subunidades constituyentes. Se describió por primera vez que la LTD ocurre en el hipocampo, donde se cree que borra viejos recuerdos. Posteriormente, se ha demostrado que la LTD ocurre en muchas regiones del cerebro, como el cerebelo, el cuerpo estriado y la corteza. La presencia ubicua de LTD subraya su importancia en el funcionamiento adecuado del cerebro. <h4>LTD y enfermedad</h4> Se cree que los mecanismos defectuosos de LTD contribuyen a numerosos trastornos neurológicos y cognitivos, como la adicción, el retraso mental y la enfermedad de Alzheimer. Se están realizando investigaciones para comprender mejor los mecanismos de LTD, cómo ocurren los trastornos neurológicos y desarrollar tratamientos.

Depresión a largo plazo

La depresión a largo plazo, o LTD, es una de las formas en que la plasticidad sináptica (cambios en la fuerza de las sinapsis químicas) puede ocurrir en el ...

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TÉRMINOS Y CONCEPTOS CLAVE

Long-term Depression

synaptic pruning in long-term depression

Long-term depression, or LTD, is a form of synaptic plasticity that weakens chemical synapses over time. It acts between presynaptic and postsynaptic neurons. LTD works in opposition to long-term potentiation, or LTP, which strengthens synapses. Together, LTD and LTP are two of the main mechanisms behind learning and memory.

LTD helps the brain avoid staying locked in a fully strengthened state. If synapses were always maximally strengthened, the brain would become less efficient and it would be harder to learn new information or form new memories. By weakening weaker synapses, LTD helps prune connections and restore flexibility to the central nervous system.

One common LTD mechanism depends on calcium ions in the postsynaptic neuron after presynaptic stimulation. When presynaptic activity is infrequent or low, calcium ion influx is also low. This leads to a low calcium ion concentration in the postsynaptic cell. That signal starts a cascade that removes AMPA glutamate receptors from the plasma membrane through endocytosis.

With fewer AMPA receptors on the membrane, the postsynaptic response to the same weak presynaptic signal becomes even smaller. Fewer channels are available for positively charged ions to enter and depolarize the membrane. The neuron can later reuse these AMPA receptors or break them into subunits.

LTD was first described in the hippocampus, where it is thought to help clear old memories. It has also been found in the cerebellum, striatum, and cortex. Because LTD appears in many brain regions, it is an important part of normal brain function. Problems with LTD are thought to play a role in addiction, mental retardation, and Alzheimer’s disease, so researchers continue to study it and possible treatments.

Synaptic Pruning in Long-term Depression

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Long-term potentiation, or LTP, is a form of synaptic strengthening in the brain. It changes the strength of chemical synapses over time between pre- and postsynaptic neurons. LTP works against long-term depression, or LTD, which weakens synapses. Together, LTP and LTD are major mechanisms behind learning and memory. LTP can happen when a presynaptic neuron fires again and again and keeps stimulating a postsynaptic neuron. This is called Hebbian LTP, based on Donald Hebb’s idea that neurons...

long-term depression

Long-term depression, or LTD, is a form of synaptic plasticity that weakens chemical synapses over time. It acts between presynaptic and postsynaptic neurons. LTD works in opposition to long-term potentiation, or LTP, which strengthens synapses. Together, LTD and LTP are two of the main mechanisms behind learning and memory. LTD helps the brain avoid staying locked in a fully strengthened state. If synapses were always maximally strengthened, the brain would become less efficient and it would...

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key terms and concepts

Learn how long-term depression weakens synapses, removes AMPA receptors, and supports learning, memory, and brain flexibility in high school biology.

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Synaptic Pruning in Long-term Depression

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