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

- [演讲人] 长时程抑制或LTD
 
 是在突触前和突触后神经元连接之间
 
 随时间发生的突触减弱的过程
 
 LTD发生的一种机制
 
 取决于突触前刺激后
 
 流入突触后神经元
 
 钙离子的量
 
 由于罕见的突触前刺激
 
 导致低钙浓度
 
 可以启动信号级联
 
 最终导致内吞作用
 
 或从膜上除去AMPA谷氨酸受体
 
 结果 对相同的散发性突触前刺激
 
 的突触后反应
 
 进一步减弱
 
 因此 LTD对于学习很重要
 
 因为未使用或很少使用的突触被削弱
 
 甚至可以被修剪掉
 
 释放神经元可用于
 
 其他功能的资源和空间
 
 比如LTP加强了更重要的突触

库库什金、尼古拉·瓦迪莫维奇和托马斯·詹姆斯·卡鲁。"记忆需要时间。"神经元 95，第 2 期（2017 年 7 月 19 日）:259-79。[<a href="https://doi.org/10.1016/j.neuron.2017.05.029" target="__blank">来源</a>]

Lüscher、Christian 和 Robert C. Malenka。"NMDA 受体依赖性长期增强和长期抑郁 （LTP/LTD）。"冷泉港生物学观点 4，第 6 期（2012 年 6 月 1 日）:a005710。[<a href="https://doi.org/10.1101/cshperspect.a005710" target="__blank">来源</a>]

长期抑郁

长期抑郁（long-term depression，简称LTD）是大脑中突触可塑性（synaptic plastics）改变化学突触强度的方式之一。LTD是突触前和突触后神经元连接之间的突触减弱过程。长期抑郁（LTD）的突触减弱与长期增强作用（long-term potentiation，简称LTP）的突触增强相反，共同作用是学习和记忆的主要机制。
<h4>钙离子富集机理</h4>
 
 如果随着时间的推移，所有的突触通过长期增强作用（LTP）或其它机制被最大程度地增强，大脑将在效率上变得稳定，使得学习和形成新的记忆变得困难。长期抑郁（LTD）是一种修剪较弱突触的方法，从而释放资源并将柔韧性带回中枢神经系统。LTD的发生机制之一依赖于突触前刺激后突触后神经元中钙离子的数量。突触前不经常或低水平的刺激导致低钙离子内流，从而导致突触后神经元低钙离子浓度。
 
 低钙离子浓度引发一个信号级联，最终导致细胞内吞或从质膜上去除α-氨基-3-羟基-5-甲基-4-异恶唑雷普酸（AMPA）谷氨酸受体。结果，相同的偶发性突触前刺激的突触后反应进一步减弱，因为正电荷离子进入和去极化膜的通道较少。神经元稍后再利用AMPA受体和/或将其分离为其组成亚单位。
 
 长期抑郁（LTD）最初被描述为发生在海马体，在那里它被认为可以清除旧的记忆。随后，LTD被证明出现在许多脑区，如小脑、纹状体和皮层。LTD无处不在的存在是其在大脑正常功能中的重要性的基础。
 
<h4> 长期抑郁与疾病</h4>
 
 长期抑郁（LTD）的功能障碍机制被认为是导致许多神经和认知障碍的原因，如成瘾、智力低下和阿尔茨海默病。目前正在进行研究，以更好地了解LTD的机制、神经系统疾病是如何发生的，并开发治疗方法。

长时程抑制（LTD）是突触可塑性——即化学突触传递强度发生改变——的一种发生方式，在……中出现

Education

教育

JoVE Core

Biology

生物学

Human Biology

人类生物学

Nervous System

神经系统

KEY TERMS AND CONCEPTS

关键术语与概念

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

what is a nervous system?

Nervous System Parts and Control

The nervous system is a network of specialized cells that keeps the body working and helps it respond to the world around it. It controls essential functions such as heart rate and breathing. It also supports movement that helps an organism escape danger. In vertebrates, the nervous system has two major parts: the central nervous system, or CNS, and the peripheral nervous system, or PNS. The CNS includes the brain, spinal cord, and retina, which is the sensory tissue of the visual system. The...

the parasympathetic nervous system

Rest and Digest: Parasympathetic Control

The parasympathetic nervous system helps the body stay calm and return to a rested state. It is one of the two major divisions of the autonomic nervous system, which controls many unconscious functions such as heart rate and digestion. Its neurons are found in the brain and the peripheral nervous system, and they send axons to muscles, organs, and glands. This system is often called the “rest and digest” system because it supports body processes that restore homeostasis. It is most active...

the sympathetic nervous system

Sympathetic Stress Response and Body Changes

The sympathetic nervous system helps the body respond to stress and danger. It is one of the two main divisions of the autonomic nervous system. When it turns on, it prepares the body for action and puts lower-priority functions, such as digestion, on hold. This response is often called the fight-or-flight system. A surprise exam can trigger it, and students may notice a tight stomach, a dry mouth, and a fast heartbeat. In a real threat, the system shifts blood away from the digestive system...

the blood-brain barrier

How the Blood-Brain Barrier Works

The blood-brain barrier is a specialized system of blood vessels that helps control what enters the brain. It delivers nutrients from the blood while tightly regulating ions, molecules, pathogens, and other substances. This semipermeable barrier protects the brain and also makes it harder to deliver some therapies. The blood-brain barrier includes several cellular parts, especially endothelial cells and astrocytes. These cells share a common basement membrane and regulate movement between the...

neuron structure

How Neurons Send Signals

Neurons send signals through a clear set of structures that let them receive, process, and pass on information. They are the main cells of the nervous system and use electrochemical signals to communicate. Neurons also talk to other cells through neurotransmitters at junctions called synapses. Most neurons share three main parts: a cell body, also called the soma, dendrites, and an axon. The soma holds the nucleus and other organelles needed for cell function. Dendrites usually receive...

glial cells

Glial Cells and Nervous System Support

Glial cells support the nervous system and work alongside neurons. They are one of the two main cell types in the nervous system. Unlike neurons, glia do not send electrical signals, but they help with nearly every other part of nervous system function. In humans, glial cells are about as numerous as neurons in the brain. In the central nervous system, glia include astrocytes, oligodendrocytes, microglia, and ependymal cells. Astrocytes are the most common glial cells. They form organized,...

action potentials

How Nerve Signals Travel in Axons

Neurons send signals through action potentials, the rapid electrical changes that move along the axon. These signals lead to neurotransmitter release at axon terminals, which passes information through the nervous system. An action potential is an all-or-none change in membrane potential, the voltage across a cell membrane. A neuron usually has a resting membrane potential of about -70 millivolts. When it receives signals from neurotransmitters or sensory input, the membrane can become more...

the resting membrane potential

How Neurons Keep a Negative Resting Charge

Neurons keep a negative resting charge across their membrane. This electrical difference, called the membrane potential, comes from how ions move and how the membrane lets them pass. In a resting neuron, the inside is typically around -70 millivolts and is more negative than the outside, so the cell is polarized. Two main factors create this resting state. First, the membrane is selectively permeable, which means most ions and molecules cannot cross the lipid bilayer without help from ion...

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

How Neurons Signal at Synapses

Neurons communicate through synapses, the points where two neurons meet to pass on signals. At a synapse, the sending neuron is the presynaptic cell, and the receiving neuron is the postsynaptic cell. Most neurons can serve in both roles because they send and receive information. Electrical synapses move signals directly between cells. The presynaptic and postsynaptic cells are linked by gap junctions, which are proteins that physically connect them. This type of synapse can pass electrical...

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.

Synaptic Pruning in Long-term Depression | JoVE K12

JoVE Core series brings biology to life through over 300 concise and easy-to-understand animated video lessons that explain key concepts in biology, plus more than 150 scientist-in-action videos that show actual research experiments conducted in today’s laboratories.

biology

JoVE Core系列通过300多节动画视频课简明易懂地讲解生物学中的关键概念，以及150余段视频展示科学家在现代实验室开展实际研究实验，让生物学变得平易近人。

myJoVE Corporation

Synaptic Pruning in Long-term Depression

Description

Transcript

Tags