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

долгосрочная депрессия или LTD это процесс синаптического ослабления, которое возникает со временем между пре-и постсинаптическими нейронными связями. Один механизм, с помощью которого происходит LTD, зависит от количества ионов кальция, попадающих в постсинаптический нейрон после пресинаптической стимуляции. Низкая концентрация кальция из-за нечастой пре-синаптической стимуляции может инициировать сигнальный каскад, который приводит к эндоцитозу или удалению рецепторов глютамата AMPA из мембраны.В результате, постсинаптический ответ на ту же спорадическую пресинаптическую стимуляцию ещё более ослаблен. Таким образом, LTD важна для обучения, так как неиспользуемые или редко используемые синапсы ослабляются и даже могут быть обрезаны для высвобождения ресурсов и пространства, которые могут использоваться нейроном для других функций, таких как укрепление LTP более важных синапсов. наптический ответ той же пре-синаптической стимуляции.LTP имеет важное значение для обучения, и это один из способов объяснить важность практики, поскольку вновь усиленный ответ может длиться от минут до недель или дольше, если пресинаптическая стимуляция сохраняется.

Кукушкин, Николай Вадимович и Томас Джеймс Кэрью. "Память требует времени." Нейрон 95, No2 (19 июля 2017 г.): 259–79. [<a href="https://doi.org/10.1016/j.neuron.2017.05.029" target="__blank">Источник</a>]

Люшер, Кристиан и Роберт К. Маленка. "NMDA-рецептор-зависимая долгосрочная потенциация и долгосрочная депрессия (LTP/LTD)." Перспективы Колд-Спринг-Харбор в биологии 4, No6 (1 июня 2012 г.): a005710. [<a href="https://doi.org/10.1101/cshperspect.a005710" target="__blank">Источник</a>]

Долговременная депрессия

Долгосрочная депрессия, или LTD, является одним из способов, с помощью которых синаптической пластичности-изменения в силе химических синапсов-может произойти в головном мозге. LTD это процесс синаптической ослабления, что происходит с течением времени между до и постсинаптических нейронных связей. Синаптическое ослабление LTD работает в оппозиции к синаптической укрепления путем долгосрочного потенции (LTP) и вместе являются основными механизмами, которые лежат в основе обучения и памяти.

<h4>Механизм концентрации ионов кальция</h4>

Если с течением времени, все синапсы максимально укреплены через LTP или какой-либо другой механизм, мозг будет плато в эффективности решений обучения и формирования новых воспоминаний трудно. LTD это способ подрезать слабые синапсы тем самым высвободив ресурсы и положить гибкость обратно в центральную нервную систему. Один механизм LTD зависит от количества ионов кальция в постсинаптических нейронах после пресинаптической стимуляции. Нечастые или низкие уровни пресинаптической стимуляции приводят к низкому притоку ионов кальция и, следовательно, низкой концентрации ионов кальция в постсинаптических нейронах.

Низкая концентрация ионов кальция инициирует сигнальный каскад, который завершается эндоцитозом или удалением из плазменной мембраны рецепторов глутамата no-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA). В результате, постсинаптическая реакция на ту же спорадическую пресинаптическую стимуляцию еще больше ослабевает, так как есть меньше каналов для положительно заряженных ионов для входа и деполяризации мембраны. Нейрон повторно использовать рецепторы АМРА на более позднее время и / или отделяет их в свои составные подразделения.

LTD был впервые описан как происходящих в гиппокампе, где он, как полагают, очистить старые воспоминания. Впоследствии было показано, что LTD происходит во многих областях мозга, таких как мозжечок, стриатум и кора головного мозга. Повсеместное присутствие LTD лежит в основе его важности в надлежащем функционировании мозга.

<h4>LTD и болезни</h4>

Неисправные механизмы LTD, как полагают, способствуют многочисленным неврологическим и когнитивным расстройствам, таким как зависимость, умственная отсталость и болезнь Альцгеймера. Исследования продолжаются, чтобы лучше понять механизмы LTD, как неврологические расстройства происходят, и разработать методы лечения.

Долгосрочная депрессия, или LTD, является одним из способов, с помощью которых синаптическая пластичность — изменения в силе химических синапсов — может происходить в ...

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ОСНОВНЫЕ ТЕРМИНЫ И ПОНЯТИЯ

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

Synaptic Strengthening in Learning and Memory

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...

the synapse

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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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