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Alpha-2 adrenergic receptor
The alpha-2 (α2) adrenergic receptor (or adrenoceptor) is a G protein-coupled receptor (GPCR) associated with the Gi heterotrimeric G-protein. It consists of three homologous subtypes, α2A-, α2B-, and α2C-adrenergic. Some species other than humans express a fourth α2D-adrenergic receptor as well. Catecholamines like norepinephrine (noradrenaline) and epinephrine (adrenaline) signal through the α2-adrenergic receptor in the central and peripheral nervous systems.
The α2A adrenergic receptor is localised in the following central nervous system (CNS) structures:
Whereas the α2B adrenergic receptor is localised in the following CNS structures:
and the α2C adrenergic receptor is localised in the CNS structures:
The α2-adrenergic receptor is classically located on vascular prejunctional terminals where it inhibits the release of norepinephrine (noradrenaline) in a form of negative feedback. It is also located on the vascular smooth muscle cells of certain blood vessels, such as those found in skin arterioles or on veins, where it sits alongside the more plentiful α1-adrenergic receptor. The α2-adrenergic receptor binds both norepinephrine released by sympathetic postganglionic fibers and epinephrine (adrenaline) released by the adrenal medulla, binding norepinephrine with slightly higher affinity. It has several general functions in common with the α1-adrenergic receptor, but also has specific effects of its own. Agonists (activators) of the α2-adrenergic receptor are frequently used in anaesthesia where they affect sedation, muscle relaxation and analgesia through effects on the central nervous system (CNS).
In the brain, α2-adrenergic receptors can be localized either pre- or post-synaptically, however the majority of receptors appear to be post-synaptic. For example, the α2A adrenergic receptor subtype is post-synaptic in the prefrontal cortex, where these receptors strengthen cognitive and executive functions by inhibiting cAMP opening of potassium channels, thus enhancing prefrontal connections and neuronal firing. The α2A-adrenergic agonist, guanfacine, is now used to treat prefrontal cortical cognitive disorders such as attention deficit hyperactivity disorder (ADHD).
Common effects include:
Individual actions of the α2 receptor include:
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Alpha-2 adrenergic receptor
The alpha-2 (α2) adrenergic receptor (or adrenoceptor) is a G protein-coupled receptor (GPCR) associated with the Gi heterotrimeric G-protein. It consists of three homologous subtypes, α2A-, α2B-, and α2C-adrenergic. Some species other than humans express a fourth α2D-adrenergic receptor as well. Catecholamines like norepinephrine (noradrenaline) and epinephrine (adrenaline) signal through the α2-adrenergic receptor in the central and peripheral nervous systems.
The α2A adrenergic receptor is localised in the following central nervous system (CNS) structures:
Whereas the α2B adrenergic receptor is localised in the following CNS structures:
and the α2C adrenergic receptor is localised in the CNS structures:
The α2-adrenergic receptor is classically located on vascular prejunctional terminals where it inhibits the release of norepinephrine (noradrenaline) in a form of negative feedback. It is also located on the vascular smooth muscle cells of certain blood vessels, such as those found in skin arterioles or on veins, where it sits alongside the more plentiful α1-adrenergic receptor. The α2-adrenergic receptor binds both norepinephrine released by sympathetic postganglionic fibers and epinephrine (adrenaline) released by the adrenal medulla, binding norepinephrine with slightly higher affinity. It has several general functions in common with the α1-adrenergic receptor, but also has specific effects of its own. Agonists (activators) of the α2-adrenergic receptor are frequently used in anaesthesia where they affect sedation, muscle relaxation and analgesia through effects on the central nervous system (CNS).
In the brain, α2-adrenergic receptors can be localized either pre- or post-synaptically, however the majority of receptors appear to be post-synaptic. For example, the α2A adrenergic receptor subtype is post-synaptic in the prefrontal cortex, where these receptors strengthen cognitive and executive functions by inhibiting cAMP opening of potassium channels, thus enhancing prefrontal connections and neuronal firing. The α2A-adrenergic agonist, guanfacine, is now used to treat prefrontal cortical cognitive disorders such as attention deficit hyperactivity disorder (ADHD).
Common effects include:
Individual actions of the α2 receptor include: