A neurotransmitter receptor (also known as a neuroreceptor) is a membrane receptor protein that is activated by a

neurotransmitter A neurotransmitter is a signaling molecule secreted by a neuron to affect another cell across a Chemical synapse, synapse. The cell receiving the signal, or target cell, may be another neuron, but could also be a gland or muscle cell. Neurotra ...

. Chemicals on the outside of the cell, such as a neurotransmitter, can bump into the cell's membrane, in which there are receptors. If a neurotransmitter bumps into its corresponding receptor, they will bind and can trigger other events to occur inside the cell. Therefore, a membrane

receptor Receptor may refer to: * Sensory receptor, in physiology, any neurite structure that, on receiving environmental stimuli, produces an informative nerve impulse *Receptor (biochemistry), in biochemistry, a protein molecule that receives and respond ...

is part of the molecular machinery that allows cells to

communicate Communication is commonly defined as the transmission of information. Its precise definition is disputed and there are disagreements about whether unintentional or failed transmissions are included and whether communication not only transmit ...

with one another. A neurotransmitter receptor is a class of receptors that specifically binds with neurotransmitters as opposed to other molecules. In postsynaptic cells, neurotransmitter receptors receive signals that trigger an electrical signal, by regulating the activity of

ion channel Ion channels are pore-forming membrane proteins that allow ions to pass through the channel pore. Their functions include establishing a resting membrane potential, shaping action potentials and other electrical signals by Gating (electrophysiol ...

s. The influx of ions through ion channels opened due to the binding of neurotransmitters to specific receptors can change the membrane potential of a neuron. This can result in a signal that runs along the

axon An axon (from Greek ἄξων ''áxōn'', axis) or nerve fiber (or nerve fibre: see American and British English spelling differences#-re, -er, spelling differences) is a long, slender cellular extensions, projection of a nerve cell, or neuron, ...

(see

action potential An action potential (also known as a nerve impulse or "spike" when in a neuron) is a series of quick changes in voltage across a cell membrane. An action potential occurs when the membrane potential of a specific Cell (biology), cell rapidly ri ...

) and is passed along at a synapse to another neuron and possibly on to a

neural network A neural network is a group of interconnected units called neurons that send signals to one another. Neurons can be either biological cells or signal pathways. While individual neurons are simple, many of them together in a network can perfor ...

. On

presynaptic In the nervous system, a synapse is a structure that allows a neuron (or nerve cell) to pass an electrical or chemical signal to another neuron or a target effector cell. Synapses can be classified as either chemical or electrical, depending o ...

cells, there are receptors known as

autoreceptor An autoreceptor is a type of Receptor (biochemistry), receptor located in the cell membrane, membranes of neuron, nerve cells. It serves as part of a negative feedback loop in signal transduction. It is only sensitive to the neurotransmitters or ...

s that are specific to the neurotransmitters released by that cell, which provide feedback and mediate excessive neurotransmitter release from it. There are two major types of neurotransmitter receptors: ''ionotropic'' and ''metabotropic''.

Ionotropic Ligand-gated ion channels (LICs, LGIC), also commonly referred to as ionotropic receptors, are a group of transmembrane ion-channel proteins which open to allow ions such as Na+, K+, Ca2+, and/or Cl− to pass through the membrane in res ...

means that ions can pass through the receptor, whereas metabotropic means that a second messenger inside the cell relays the message (i.e. metabotropic receptors do not have channels). There are several kinds of metabotropic receptors, including

G protein-coupled receptor G protein-coupled receptors (GPCRs), also known as seven-(pass)-transmembrane domain receptors, 7TM receptors, heptahelical receptors, serpentine receptors, and G protein-linked receptors (GPLR), form a large group of evolutionarily related ...

s. Ionotropic receptors are also called

ligand-gated ion channels Ligand-gated ion channels (LICs, LGIC), also commonly referred to as ionotropic receptors, are a group of transmembrane ion-channel proteins which open to allow ions such as Na+, K+, Ca2+, and/or Cl− to pass through the membrane in res ...

and they can be activated by neurotransmitters (

ligand In coordination chemistry, a ligand is an ion or molecule with a functional group that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's el ...

s) like

glutamate Glutamic acid (symbol Glu or E; known as glutamate in its anionic form) is an α-amino acid that is used by almost all living beings in the biosynthesis of proteins. It is a Essential amino acid, non-essential nutrient for humans, meaning that ...

and

GABA GABA (gamma-aminobutyric acid, γ-aminobutyric acid) is the chief inhibitory neurotransmitter in the developmentally mature mammalian central nervous system. Its principal role is reducing neuronal excitability throughout the nervous system. GA ...

, which then allow specific ions through the membrane. Sodium ions (that are, for example, allowed passage by the

glutamate receptor Glutamate receptors are synaptic and non synaptic receptors located primarily on the membranes of neuronal and glial cells. Glutamate (the conjugate base of glutamic acid) is abundant in the human body, but particularly in the nervous system ...

) excite the post-synaptic cell, while chloride ions (that are, for example, allowed passage by the GABA receptor) inhibit the post-synaptic cell. Inhibition reduces the chance that an

will occur, while excitation increases the chance. Conversely, G-protein-coupled receptors are neither excitatory nor inhibitory. Rather, they can have a broad number of functions such as modulating the actions of excitatory and inhibitory ion channels or triggering a signalling cascade that releases calcium from stores inside the cell. Most neurotransmitters receptors are G-protein coupled.

Localization

Neurotransmitter (NT) receptors are located on the surface of

neuron A neuron (American English), neurone (British English), or nerve cell, is an membrane potential#Cell excitability, excitable cell (biology), cell that fires electric signals called action potentials across a neural network (biology), neural net ...

al and

glia Glia, also called glial cells (gliocytes) or neuroglia, are non-neuronal cells in the central nervous system (the brain and the spinal cord) and in the peripheral nervous system that do not produce electrical impulses. The neuroglia make up ...

l cells. At a

synapse In the nervous system, a synapse is a structure that allows a neuron (or nerve cell) to pass an electrical or chemical signal to another neuron or a target effector cell. Synapses can be classified as either chemical or electrical, depending o ...

, one neuron sends messages to the other neuron via neurotransmitters. Therefore, the postsynaptic neuron, the one receiving the message, clusters NT receptors at this specific place in its membrane. NT receptors can be inserted into any region of the neuron's membrane such as dendrites, axons, and the cell body. Receptors can be located in different parts of the body to act as either an inhibitor or an excitatory receptor for a specific Neurotransmitter Goldman, B. (2010, November 17). New imaging method developed at Stanford reveals stunning details of brain connections. In Stanford medicine news center. Retrieved from https://med.stanford.edu/news/all-news/2010/11/new-imaging-method-developed-at-stanford-reveals-stunning-details-of-brain-connections.html. An example of this are the receptors for the neurotransmitter Acetylcholine (ACh), one receptor is located at the neuromuscular junction in skeletal muscle to facilitate muscle contraction (excitation), while the other receptor is located in the heart to slow down heart rate (inhibitory)

Ionotropic receptors: neurotransmitter-gated ion channels

Ligand-gated ion channels Ligand-gated ion channels (LICs, LGIC), also commonly referred to as ionotropic receptors, are a group of transmembrane ion-channel proteins which open to allow ions such as Na+, K+, Ca2+, and/or Cl− to pass through the membrane in res ...

(LGICs) are one type of ionotropic receptor or channel-linked receptor. They are a group of

transmembrane A transmembrane protein is a type of integral membrane protein that spans the entirety of the cell membrane. Many transmembrane proteins function as gateways to permit the transport of specific substances across the membrane. They frequently u ...

s that are opened or closed in response to the binding of a chemical messenger (i.e., a

), such as a

. The binding site of

endogenous Endogeny, in biology, refers to the property of originating or developing from within an organism, tissue, or cell. For example, ''endogenous substances'', and ''endogenous processes'' are those that originate within a living system (e.g. an ...

ligands on LGICs protein complexes are normally located on a different portion of the protein (an

allosteric In the fields of biochemistry and pharmacology an allosteric regulator (or allosteric modulator) is a substance that binds to a site on an enzyme or receptor distinct from the active site, resulting in a conformational change that alters the p ...

binding site) compared to where the ion conduction pore is located. The direct link between ligand binding and opening or closing of the ion channel, which is characteristic of ligand-gated ion channels, is contrasted with the indirect function of metabotropic receptors, which use

second messenger Second messengers are intracellular signaling molecules released by the cell in response to exposure to extracellular signaling molecules—the first messengers. (Intercellular signals, a non-local form of cell signaling, encompassing both first m ...

s. LGICs are also different from

voltage-gated ion channel Voltage-gated ion channels are a class of transmembrane proteins that form ion channels that are activated by changes in a Cell (biology), cell's electrical membrane potential near the channel. The membrane potential alters the conformation of t ...

s (which open and close depending on

membrane potential Membrane potential (also transmembrane potential or membrane voltage) is the difference in electric potential between the interior and the exterior of a biological cell. It equals the interior potential minus the exterior potential. This is th ...

), and

stretch-activated ion channel Mechanosensitive channels (MSCs), mechanosensitive ion channels or stretch-gated ion channels are membrane proteins capable of responding to mechanical stress over a wide dynamic range of external mechanical stimuli. They are present in the memb ...

s (which open and close depending on mechanical deformation of the

cell membrane The cell membrane (also known as the plasma membrane or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the interior of a cell from the outside environment (the extr ...

Metabotropic receptors: G-protein coupled receptors

G protein-coupled receptors G protein-coupled receptors (GPCRs), also known as seven-(pass)-transmembrane domain receptors, 7TM receptors, heptahelical receptors, serpentine receptors, and G protein-linked receptors (GPLR), form a large protein family, group of evoluti ...

(GPCRs), also known as seven-transmembrane domain receptors, 7TM receptors, heptahelical receptors, serpentine receptor, and G protein-linked receptors (GPLR), comprise a large

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...

family of

transmembrane receptor Cell surface receptors (membrane receptors, transmembrane receptors) are receptor (biochemistry), receptors that are embedded in the cell membrane, plasma membrane of cell (biology), cells. They act in cell signaling by receiving (binding to) ex ...

s that sense

molecule A molecule is a group of two or more atoms that are held together by Force, attractive forces known as chemical bonds; depending on context, the term may or may not include ions that satisfy this criterion. In quantum physics, organic chemi ...

s outside the cell and activate inside

signal transduction Signal transduction is the process by which a chemical or physical signal is transmitted through a cell as a biochemical cascade, series of molecular events. Proteins responsible for detecting stimuli are generally termed receptor (biology), rece ...

pathways and, ultimately, cellular responses. G protein-coupled receptors are found only in

eukaryote The eukaryotes ( ) constitute the Domain (biology), domain of Eukaryota or Eukarya, organisms whose Cell (biology), cells have a membrane-bound cell nucleus, nucleus. All animals, plants, Fungus, fungi, seaweeds, and many unicellular organisms ...

s, including yeast,

choanoflagellate Choanoflagellates are a group of free-living unicellular and colonial flagellate eukaryotes considered to be the closest living relatives of animals. The name refers to the characteristic funnel-shaped "collar" of interconnected microvilli and ...

s, and animals. The

ligands In coordination chemistry, a ligand is an ion or molecule with a functional group that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's ...

that bind and activate these receptors include light-sensitive compounds,

odor An odor (American English) or odour ( Commonwealth English; see spelling differences) is a smell or a scent caused by one or more volatilized chemical compounds generally found in low concentrations that humans and many animals can perceive ...

pheromone A pheromone () is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting like hormones outside the body of the secreting individual, to affect the behavio ...

hormone A hormone (from the Ancient Greek, Greek participle , "setting in motion") is a class of cell signaling, signaling molecules in multicellular organisms that are sent to distant organs or tissues by complex biological processes to regulate physio ...

s, and

s, and vary in size from small molecules to

peptide Peptides are short chains of amino acids linked by peptide bonds. A polypeptide is a longer, continuous, unbranched peptide chain. Polypeptides that have a molecular mass of 10,000 Da or more are called proteins. Chains of fewer than twenty am ...

s to large

s. G protein-coupled receptors are involved in many diseases, and are also the target of approximately 30% of all modern medicinal drugs. There are two principal signal transduction pathways involving the G protein-coupled receptors: the cAMP signal pathway and the

phosphatidylinositol Phosphatidylinositol or inositol phospholipid is a biomolecule. It was initially called "inosite" when it was discovered by Léon Maquenne and Johann Joseph von Scherer in the late 19th century. It was discovered in bacteria but later also found ...

signal pathway. When a ligand binds to the GPCR it causes a conformational change in the GPCR, which allows it to act as a

guanine nucleotide exchange factor Guanine nucleotide exchange factors (GEFs) are proteins or protein domains that activate monomeric GTPases by stimulating the release of guanosine diphosphate (GDP) to allow binding of guanosine triphosphate (GTP). A variety of unrelated structu ...

(GEF). The GPCR can then activate an associated G-protein by exchanging its bound GDP for a GTP. The G-protein's α subunit, together with the bound GTP, can then dissociate from the β and γ subunits to further affect intracellular signaling proteins or target functional proteins directly depending on the α subunit type ( G_αs, G_αi/o, G_αq/11, G_α12/13).

Desensitization and neurotransmitter concentration

Neurotransmitter receptors are subject to ligand-induced desensitization: That is, they can become unresponsive upon prolonged exposure to their neurotransmitter. Neurotransmitter receptors are present on both postsynaptic neurons ''and'' presynaptic neurons with the former being used to receive

s and the latter for the purpose of preventing further release of a given neurotransmitter. In addition to being found in neuron cells, neurotransmitter receptors are also found in various immune and muscle tissues. Many neurotransmitter receptors are categorized as a serpentine receptor or

because they span the cell membrane not once, but seven times. Neurotransmitter receptors are known to become unresponsive to the type of

they receive when exposed for extended periods of time. This phenomenon is known as ligand-induced desensitization or

downregulation In biochemistry, in the biology, biological context of organisms' regulation of gene expression and production of gene products, downregulation is the process by which a cell (biology), cell decreases the production and quantities of its cellular ...

Example neurotransmitter receptors

The following are some major classes of neurotransmitter receptors:ed. Kebabain, J. W. & Neumeyer, J. L. (1994). "RBI Handbook of Receptor Classification" *

Adrenergic Adrenergic means "working on adrenaline (epinephrine) or noradrenaline (norepinephrine)" (or on their receptors). When not further qualified, it is usually used in the sense of enhancing or mimicking the effects of epinephrine and norepinephrine ...

: α_1A, α_1b, α_1c, α_1d, α_2a, α_2b, α_2c, α_2d, β₁, β₂, β₃ * Cholinergic: ** Muscarinic: M1, M2, M3, M4, M5 ** Nicotinic: muscle, neuronal (α-bungarotoxin-insensitive), neuronal (α-bungarotoxin-sensitive) *

Dopaminergic Dopaminergic means "related to dopamine" (literally, "working on dopamine"), a common neurotransmitter. Dopaminergic substances or actions increase dopamine-related activity in the brain. Dopaminergic pathways, Dopaminergic brain pathways facil ...

: D₁, D₂, D₃, D₄, D₅ *

GABAergic In molecular biology and physiology, something is GABAergic or GABAnergic if it pertains to or affects the neurotransmitter gamma-aminobutyric acid (GABA). For example, a synapse is GABAergic if it uses GABA as its neurotransmitter, and a GABAergic ...

: GABA_A, GABA_B1a, GABA_B1δ, GABA_B2, GABA_C *

Glutamatergic Glutamatergic means "related to glutamate". A glutamatergic agent (or drug) is a chemical that directly modulates the excitatory amino acid (glutamate/aspartate) system in the body or brain. Examples include excitatory amino acid receptor agonist ...

: NMDA,

AMPA α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid, better known as AMPA, is a compound that is a specific agonist for the AMPA receptor, where it mimics the effects of the neurotransmitter glutamate Glutamic acid (symbol Glu or E; kn ...

, Kainate, mGluR₁, mGluR₂, mGluR₃, mGluR₄, mGluR₅, mGluR₆, mGluR₇ * Glycinergic: Glycine * Histaminergic: H₁, H₂, H₃ * Opioidergic: μ, δ₁, δ₂, κ * Serotonergic: 5-HT_1A, 5-HT_1B, 5-HT_1D, 5-HT_1E, 5-HT_1F, 5-HT_2A, 5-HT_2B, 5-HT_2C, 5-HT₃, 5-HT₄, 5-HT₅, 5-HT₆, 5-HT₇

Notes and references

External links

Brain Explorer

Snyder (2009) Neurotransmitters, Receptors, and Second Messengers Galore in 40 Years. Journal of Neuroscience. 29(41): 12717-12721.Snyder and Bennett (1976) Neurotransmitter Receptors in the Brain: Biochemical Identification. Annual Review of Physiology. Vol. 38: 153-175Library of Congress Authorities and Vocabularies: Neurotransmitter ReceptorsNeurotransmitter Receptors, Transporters, & Ion Channels
* {{DEFAULTSORT:Neurotransmitter Receptor Receptors Neurochemistry