Synaptic vesicle in the context of "Neurotransmitter transporter"

Chemical synapses are biological junctions through which neurons' signals can be sent to each other and to non-neuronal cells such as those in muscles or glands. Chemical synapses allow neurons to form circuits within the central nervous system. They are crucial to the biological computations that underlie perception and thought. They allow the nervous system to connect to and control other systems of the body.

At a chemical synapse, one neuron releases neurotransmitter molecules into a small space (the synaptic cleft) that is adjacent to the postsynaptic cell (e.g., another neuron). The neurotransmitter molecules are contained within small sacs called synaptic vesicles, and are released into the synaptic cleft by exocytosis. These molecules then bind to neurotransmitter receptors on the postsynaptic cell. Finally, to terminate its action, the neurotransmitter is cleared from the cleft through one of several mechanisms, including enzymatic degradation or re-uptake, by specific transporters, either into the presynaptic cell or to neuroglia.

Alpha-synuclein (aSyn) is a protein that in humans is encoded by the SNCA gene. It is a neuronal protein involved in the regulation of synaptic vesicle trafficking and the release of neurotransmitters.

Alpha-synuclein is abundant in the brain, with smaller amounts present in the heart, muscles, and other tissues. Within the brain, it is primarily localized to the axon terminals of presynaptic neurons. There, it interacts with phospholipids and other proteins. Presynaptic terminals release neurotransmitters from specialized compartments called synaptic vesicles, a process essential for neuronal communication and normal brain function.

Amperometry in chemistry is the detection of ions in a solution based on electric current or changes in electric current.

Amperometry is used in electrophysiology to study vesicle release events using a carbon fiber electrode. Unlike patch clamp techniques, the electrode used for amperometry is not inserted into or attached to the cell but brought nearby of the cell. The measurements from the electrode originate from an oxidizing reaction of a vesicle cargo released into the medium. Another technique used to measure vesicle release is capacitive measurements.

Axon terminals (also called terminal boutons, synaptic boutons, end-feet, or presynaptic terminals) are distal terminations of the branches of an axon. An axon, also called a nerve fiber, is a long, slender projection of a nerve cell that conducts electrical impulses called action potentials away from the neuron's cell body to transmit those impulses to other neurons, muscle cells, or glands. Most presynaptic terminals in the central nervous system are formed along the axons (en passant boutons), not at their ends (terminal boutons).

Functionally, the axon terminal converts an electrical signal into a chemical signal. When an action potential arrives at an axon terminal (A), the neurotransmitter is released and diffuses across the synaptic cleft. If the postsynaptic cell (B) is also a neuron, neurotransmitter receptors generate a small electrical current that changes the postsynaptic potential. If the postsynaptic cell (B) is a muscle cell (neuromuscular junction), it contracts.

Exocytosis (/ˌɛksoʊsaɪˈtoʊsɪs/) is a form of active transport in which a cell transports molecules (e.g., neurotransmitters and proteins) out of the cell. As an active transport mechanism, exocytosis requires the use of energy to transport material. Exocytosis and its counterpart, endocytosis, are used by all cells because most chemical substances important to them are large polar molecules that cannot pass through the hydrophobic portion of the cell membrane by passive means. Exocytosis is the process by which a large amount of molecules are released; thus it is a form of bulk transport. Exocytosis occurs via secretory portals at the cell plasma membrane called porosomes. Porosomes are permanent cup-shaped lipoprotein structures at the cell plasma membrane, where secretory vesicles transiently dock and fuse to release intra-vesicular contents from the cell.

In exocytosis, membrane-bound secretory vesicles are carried to the cell membrane, where they dock and fuse at porosomes and their contents (i.e., water-soluble molecules) are secreted into the extracellular environment. This secretion is possible because the vesicle transiently fuses with the plasma membrane. In the context of neurotransmission, neurotransmitters are typically released from synaptic vesicles into the synaptic cleft via exocytosis; however, neurotransmitters can also be released via reverse transport through membrane transport proteins.

Large dense core vesicle (LDCVs) are lipid vesicles in neurons and secretory cells which may be filled with neurotransmitters, such as catecholamines or neuropeptides. LDVCs release their content through SNARE-mediated exocytosis similar to synaptic vesicles. One key difference between synaptic vesicles and LDCVs is that protein synaptophysin which is present in the membrane of synaptic vesicles is absent in LDCVs. LDCVs have an electron dense core which appears as a black circle in micrographs obtained with transmission electron microscopy.

Glutamate transporters are a family of neurotransmitter transporter proteins that move glutamate – the principal excitatory neurotransmitter – across a membrane. The family of glutamate transporters is composed of two primary subclasses: the excitatory amino acid transporter (EAAT) family and vesicular glutamate transporter (VGLUT) family. In the brain, EAATs remove glutamate from the synaptic cleft and extrasynaptic sites via glutamate reuptake into glial cells and neurons, while VGLUTs move glutamate from the cell cytoplasm into synaptic vesicles. Glutamate transporters also transport aspartate and are present in virtually all peripheral tissues, including the heart, liver, testes, and bone. They exhibit stereoselectivity for L-glutamate but transport both L-aspartate and D-aspartate.

The EAATs are membrane-bound secondary transporters that superficially resemble ion channels. These transporters play the important role of regulating concentrations of glutamate in the extracellular space by transporting it along with other ions across cellular membranes. After glutamate is released as the result of an action potential, glutamate transporters quickly remove it from the extracellular space to keep its levels low, thereby terminating the synaptic transmission.