Alpha-1 adrenergic receptor

An alpha-1 adrenergic receptor is a G protein-coupled receptor activated by norepinephrine and epinephrine. Its signaling commonly constricts vascular smooth muscle and also affects other smooth muscles and glands.

Gq alpha subunit: A heterotrimeric G-protein subunit that activates phospholipase C beta when bound to GTP. Alpha-1 receptors couple chiefly to Gq-family proteins to initiate intracellular signaling.
G protein-coupled receptor: A membrane receptor that transmits signals by activating intracellular heterotrimeric G proteins. Alpha-1 adrenergic receptors belong to this large receptor family.
Phenylephrine: A selective alpha-1 adrenergic agonist used as a vasopressor and nasal decongestant. Its receptor activation illustrates how alpha-1-mediated vasoconstriction is used clinically.
Alpha-2 adrenergic receptor: A family of adrenergic G protein-coupled receptors that commonly signals through Gi proteins. Unlike alpha-1 receptors, alpha-2 receptors often inhibit neurotransmitter release and reduce cAMP.
Phospholipase C: An enzyme that cleaves phospholipids to generate signaling molecules such as IP3 and diacylglycerol. Gq activation stimulates this enzyme downstream of alpha-1 receptor binding.
Alpha-1A adrenergic receptor: A subtype of alpha-1 adrenergic receptor encoded by ADRA1A. This subtype is prominent in the prostate and contributes to smooth-muscle tone.
Prazosin: A selective alpha-1 adrenergic antagonist used to treat hypertension and urinary symptoms. Blocking alpha-1 receptors relaxes vascular and some urinary smooth muscle.
Beta-1 adrenergic receptor: An adrenergic G protein-coupled receptor that primarily increases heart rate and contractility. Its cardiac effects contrast with alpha-1 receptors' prominent vascular smooth-muscle actions.
Inositol trisphosphate: A soluble second messenger that binds receptors on the endoplasmic reticulum to release stored calcium. It links alpha-1 signaling to increased cytosolic calcium in smooth muscle.
Alpha-1B adrenergic receptor: A subtype of alpha-1 adrenergic receptor encoded by ADRA1B. Its distribution and signaling provide one source of tissue-specific alpha-1 effects.

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