α1-adrenergic alpha receptors are G-Protein Coupled Receptors that are involved in neurotransmission and regulate the sympathetic nervous system through binding and activating the neurotransmitter, norepinephrine, and the neurohormone, epinephrine. This receptor plays a key role in several neurological systems and several neurological diseases that are associated with the NE system.
In instances in which there is hypoperfusion secondary to decreased cardiac output or decreased systemic vasculature resistance, alpha-1 receptors become stimulated.
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Alpha-1 agonists are a class of medications used in the management of many disorders, including vasodilatory shock, hypotension, hypoperfusion, septic shock, cardiopulmonary arrest, heart failure decompensation, as well as other lower acuity conditions.
The alpha-1 adrenergic receptor antagonists (also called alpha-blockers) are a family of agents that bind to and inhibit type 1 alpha-adrenergic receptors and thus inhibit smooth muscle contraction. Their major uses are for hypertension and for symptomatic benign prostatic hypertrophy.
The increase in α1 -adrenoceptor expression after nerve and tissue injury could have important clinical implications in neuropathic pain syndromes. It becomes expressed in primary afferent nociceptors (C fibers), and releases norepinephrine, changing ion channel properties.
For Pain Management, You Want an Alpha 1 Antagonist, Such as Phentolamine.
The α2-adrenoreceptors are located on both pre-and postsynaptic neurons, where they mediate an inhibitory role in the central and peripheral nervous system. Alpha 2 receptors in the brain stem and in the periphery inhibit sympathetic activity and thus lower blood pressure.
Alpha 2 is an auto-receptor with a “feedback switch”, which can control the release of NE.
Increased activity of alpha 2 receptor inhibits NE release.
For Pain Management, You Want an Alpha 1 Agonist, Such as Clonidine.
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References
- Taylor BN, Cassagnol M. Alpha Adrenergic Receptors. [Updated 2021 Jul 13]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK539830/
- Reid JL. Central alpha 2 receptors and the regulation of blood pressure in humans. J Cardiovasc Pharmacol. 1985;7 Suppl 8:S45-50. PMID: 2417053.