ADRA2C is a member of one of three families of Alpha-2-adrenergic GPCRs that include subtypes alpha2A, alpha2B and alpha2C. These receptors are critical in regulating neurotransmitter release from adrenergic neurons and sympathetic nerves. The alpha2 subtypes are found in the central nervous systm and stimulation is associated with sedation, analgesia, and sympatholytic effects. The alpha2A subtype inhibits transmitter release at high stimulation frequencies, whereas the alpha2C subype modulates neurotransmission at lower levels of nerve activity. References: Anesth Prog. 2015 Spring; 62(1): 31–38.