Alpha-2 adrenergic receptors are spread throughout the central and peripheral nervous system, specifically in the pontine locus coeruleus, medullospinal tracts, rostral ventrolateral medulla, and the dorsal horn of the spinal cord. Alpha-2 agonist agents cause neuromodulation in these centers, leading to sedation, analgesia, vasodilatation, and bradycardia with little effect on the respiratory drive, which accounts for their good safety profile. The 2 major drugs in this group are clonidine and dexmedetomidine. Their clinical applications in anesthesia practice include providing sedation in the intensive care unit or for minor procedures, adjuvant to general and regional anesthesia, analgesia, and as premedicating agents.
Keywords: Alpha-2 adrenoreceptors; Clonidine; Dexmedetomidine; Dorsal horn; Locus coeruleus; Medullospinal tracts; Pons; Premedication.
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