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The adrenergic receptors or adrenoceptors are a class of G protein-coupled receptors that are targets of many catecholamines like norepinephrine (noradrenaline) and epinephrine (adrenaline) produced by the body, but also many medications like beta blockers, beta-2 (β 2) antagonists and alpha-2 (α 2) agonists, which are used to treat high ...
Beta blockers must not be used in the treatment of selective alpha-adrenergic agonist overdose. The blockade of only beta receptors increases blood pressure, reduces coronary blood flow, left ventricular function, and cardiac output and tissue perfusion by means of leaving the alpha-adrenergic system stimulation unopposed.
When non-selective alpha blockers are used, norepinephrine cannot bind to alpha 1 or alpha 2 receptors. [7] As a result, activation of beta receptors occurs upon norepinephrine binding due to the spillover of excessive amounts of norepinephrine , resulting in tremors and tachycardia .
Apart from increasing the noradrenaline release, the selective alpha-2 blockers have the potential to bind with other receptors such as the 5-HT serotonin receptor. [10] However, the serotonin receptor antagonism has side effects such as weight gain and impaired movement. [11] Hence, alpha-2 blockers are not used clinically due to its extensive ...
Alpha blockers, also known as α-blockers or α-adrenoreceptor antagonists, are a class of pharmacological agents that act as antagonists on α-adrenergic receptors (α-adrenoceptors). [ 2 ] Historically, alpha-blockers were used as a tool for pharmacologic research to develop a greater understanding of the autonomic nervous system.
Alpha 2 receptors are associated with sympatholytic properties. Alpha-adrenergic agonists have the opposite function of alpha blockers . Alpha adrenoreceptor ligands mimic the action of epinephrine and norepinephrine signaling in the heart, smooth muscle and central nervous system, with norepinephrine being the highest affinity.
A primary or secondary aliphatic amine separated by 2 carbons from a substituted benzene ring is minimally required for high agonist activity. The pKa of the amine is approximately 8.5-10. [2] The presence of hydroxy group in the benzene ring at 3rd and 4th position shows maximum alpha- and beta-adrenergic activity. [medical citation needed]
In general, pure beta-adrenergic agonists have the opposite function of beta blockers: beta-adrenoreceptor agonist ligands mimic the actions of both epinephrine- and norepinephrine- signaling, in the heart and lungs, and in smooth muscle tissue; epinephrine expresses the higher affinity.