Editing Neurotransmitter receptor (section)

{{Short description|Type of protein}}
[[File:PDB 1hzx 7TM Sketch Membrane.png|thumb|300px|Figure 1. The seven transmembrane α-helix structure of a G-protein-coupled receptor.]]

A '''neurotransmitter receptor''' (also known as a '''neuroreceptor''') is a membrane [[receptor protein]]<ref name="Levitan 2002">{{cite book|last=Levitan|first=Irwin B.|author2=Leonard K. Kaczmarek |title=The Neuron|publisher=Oxford University Press|year=2002|edition= Third pg. 285}}</ref> that is activated by a [[neurotransmitter]].<ref name="brainexplorer.org">{{cite web|url=http://www.brainexplorer.org/neurological_control/neurological_neurotransmitters.shtml |title=Neurological Control - Neurotransmitters |publisher=Brain Explorer |date=2011-12-20 |access-date=2012-11-04}}</ref> 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 (biochemistry)|receptor]] is part of the molecular machinery that allows cells to  [[Cell communication|communicate]] 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]]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]] (see [[action potential]]) and is passed along at a synapse to another neuron and possibly on to a [[Biological neural network|neural network]].<ref name="Levitan 2002"/> On [[presynaptic]] cells, there are receptors known as [[autoreceptor]]s that are specific to the neurotransmitters released by that cell, which provide feedback and mediate excessive neurotransmitter release from it.<ref>{{cite web|url=http://www.rndsystems.com/molecule_group.aspx?g=682&r=9|title= Neurotransmitter Receptors, Transporters, & Ion Channels|publisher=www.rndsystems.com}}</ref>

There are two major types of neurotransmitter receptors: ''ionotropic'' and ''metabotropic''. [[Ligand-gated ion channel|Ionotropic]] means that ions can pass through the receptor, whereas [[Metabotropic receptor|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]]s.<ref name="brainexplorer.org"/><ref>{{cite web|url=http://web.williams.edu/imput/synapse/pages/III.html |title=3. Neurotransmitter Postsynaptic Receptors |publisher=Web.williams.edu |access-date=2012-11-04}}</ref> Ionotropic receptors are also called [[ligand-gated ion channels]] and they can be activated by neurotransmitters ([[ligand]]s) like [[Glutamate receptor|glutamate]] and [[GABAA receptor|GABA]], which then [[Ion channel|allow specific ions]] through the membrane.  Sodium ions (that are, for example, allowed passage by the [[AMPA receptor|glutamate receptor]]) [[Excitatory postsynaptic potential|excite]] the post-synaptic cell, while chloride ions (that are, for example, allowed passage by the [[GABAA receptor|GABA receptor)]] [[Inhibitory postsynaptic potential|inhibit]] the post-synaptic cell. Inhibition reduces the chance that an [[action potential]] 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.<ref name="brainexplorer.org"/> Most neurotransmitters receptors are G-protein coupled.<ref name="Levitan 2002"/>