α2-adrenergic receptors include 3 highly homologous subtypes: α2A, α2B, and α2C. These receptors have a critical role in regulating
neurotransmitter release from
sympathetic nerves and from adrenergic neurons in the
central nervous system. Studies in mice revealed that both the α2A and α2C subtypes were required for normal
presynaptic control of transmitter release from sympathetic nerves in the
heart and from central noradrenergic neurons; the α2A subtype inhibited transmitter release at high stimulation frequencies, whereas the α2C subtype modulated neurotransmission at lower levels of nerve activity. == Gene ==