Mechanism of action of an a2 adrenergic receptor antagonist
An α2 adrenergic receptor antagonist prevents the activation of the α2 adrenergic receptor. The α2 receptor is coupled to inhibitory G-proteins, which dissociate from the receptor following agonist binding, and inhibit both secondary messenger signaling mechanisms and cell depolarisation. Antagonist binding to the α2 adrenergic receptor prevents secondary messenger inhibition and allows cell depolarisation to occur.
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References
Adrenoreceptor-activating and other sympathomimetic drugs. In: Basic and clinical pharmacology, 8th edition. Katzung BG. USA: The McGraw Hill Companies, Inc, 2001:120–137.