Target type: biologicalprocess
The active transport of neurotransmitters into a synaptic vesicle. This import is fuelled by an electrochemical gradient across the vesicle membrane, established by the action of proton pumps. [GOC:bf, GOC:pad, GOC:PARL, PMID:10099709, PMID:15217342]
Neurotransmitter loading into synaptic vesicles is a complex process that ensures the efficient and regulated release of neurotransmitters at synapses. This process involves several key steps:
1. **Synthesis:** Neurotransmitters are synthesized within the presynaptic neuron, often in the cytoplasm. The specific enzymes involved in synthesis vary depending on the neurotransmitter. For example, acetylcholine is synthesized from choline and acetyl CoA by the enzyme choline acetyltransferase, while dopamine is synthesized from tyrosine by a series of enzymatic steps.
2. **Transport:** Once synthesized, neurotransmitters must be transported into synaptic vesicles. This is an active process that requires energy and specific transporter proteins embedded in the vesicle membrane. For example, the vesicular acetylcholine transporter (VAChT) transports acetylcholine into synaptic vesicles, while the vesicular monoamine transporter (VMAT) transports dopamine, serotonin, and norepinephrine.
3. **Proton Gradient:** The transport of neurotransmitters into synaptic vesicles is driven by a proton gradient. This gradient is established by a proton pump, V-ATPase, located in the vesicle membrane. V-ATPase uses energy from ATP hydrolysis to pump protons into the vesicle, creating a high concentration of protons inside the vesicle relative to the cytoplasm.
4. **Electrochemical Gradient:** The proton gradient creates an electrochemical gradient that favors the movement of neurotransmitters into the vesicle. The positive charge of the proton gradient attracts negatively charged neurotransmitters, such as acetylcholine, while the high proton concentration drives the movement of positively charged neurotransmitters, such as dopamine, into the vesicle.
5. **Loading and Storage:** Once inside the vesicle, neurotransmitters are stored in a concentrated form. This concentration is essential for efficient release at the synapse. The storage of neurotransmitters within vesicles is facilitated by the presence of various proteins, such as synapsins, which bind to the vesicle membrane and help regulate neurotransmitter release.
6. **Release:** When an action potential arrives at the presynaptic terminal, it triggers the opening of voltage-gated calcium channels. Calcium influx into the presynaptic terminal triggers a series of events that lead to the fusion of synaptic vesicles with the presynaptic membrane, releasing neurotransmitters into the synaptic cleft.
The loading of neurotransmitters into synaptic vesicles is a tightly regulated process that is essential for neuronal communication. Disruptions in this process can lead to various neurological disorders, such as Parkinson's disease and Alzheimer's disease.'
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| Protein | Definition | Taxonomy |
|---|---|---|
| Synaptic vesicular amine transporter | A synaptic vesicular amine transporter that is encoded in the genome of human. [PRO:DNx, UniProtKB:Q05940] | Homo sapiens (human) |
| Compound | Definition | Classes | Roles |
|---|---|---|---|
| ketanserin | ketanserin : A member of the class of quinazolines that is quinazoline-2,4(1H,3H)-dione which is substituted at position 3 by a 2-[4-(p-fluorobenzoyl)piperidin-1-yl]ethyl group. Ketanserin: A selective serotonin receptor antagonist with weak adrenergic receptor blocking properties. The drug is effective in lowering blood pressure in essential hypertension. It also inhibits platelet aggregation. It is well tolerated and is particularly effective in older patients. | aromatic ketone; organofluorine compound; piperidines; quinazolines | alpha-adrenergic antagonist; antihypertensive agent; cardiovascular drug; EC 3.4.21.26 (prolyl oligopeptidase) inhibitor; serotonergic antagonist |
| reserpine | reserpine : An alkaloid found in the roots of Rauwolfia serpentina and R. vomitoria. Reserpine: An alkaloid found in the roots of Rauwolfia serpentina and R. vomitoria. Reserpine inhibits the uptake of norepinephrine into storage vesicles resulting in depletion of catecholamines and serotonin from central and peripheral axon terminals. It has been used as an antihypertensive and an antipsychotic as well as a research tool, but its adverse effects limit its clinical use. | alkaloid ester; methyl ester; yohimban alkaloid | adrenergic uptake inhibitor; antihypertensive agent; EC 3.4.21.26 (prolyl oligopeptidase) inhibitor; environmental contaminant; first generation antipsychotic; plant metabolite; xenobiotic |
| tetrabenazine | 9,10-dimethoxy-3-isobutyl-1,3,4,6,7,11b-hexahydro-2H-pyrido[2,1-a]isoquinolin-2-one : A benzoquinolizine that is 1,2,3,4,4a,9,10,10a-octahydrophenanthrene in which the carbon at position 10a is replaced by a nitrogen and which is substituted by an isobutyl group at position 2, an oxo group at position 3, and methoxy groups at positions 6 and 7. | benzoquinolizine; cyclic ketone; tertiary amino compound | |
| 2h-benzo(a)quinolizin-2-ol, 2-ethyl-1,3,4,6,7,11b-hexahydro-3-isobutyl-9,10-dimethoxy- | 2H-Benzo(a)quinolizin-2-ol, 2-Ethyl-1,3,4,6,7,11b-hexahydro-3-isobutyl-9,10-dimethoxy-: Proposed catecholamine depletor. | ||
| lobeline | (-)-lobeline : An optically active piperidine alkaloid having a 2-oxo-2-phenylethyl substituent at the 2-position and a 2-hydroxy-2-phenylethyl group at the 6-position. | aromatic ketone; piperidine alkaloid; tertiary amine | nicotinic acetylcholine receptor agonist |
| dihydrotetrabenazine | dihydrotetrabenazine: RN given refers to cpd without isomeric designation | isoquinolines | |
| lobeline | |||
| lobelane | lobelane: structure in first source | ||
| mrk 560 | MRK 560: a gamma-secretase inhibitor; MRK-560 is the (cis)-isomer; structure in first source |