NCIt definition : Expressed by Alpha Adrenergic Receptor Genes in effector tissues innervated by postganglionic
sympathetic adrenergic fibers, Alpha Adrenergic Receptors are one of two major classes
of adrenergic receptors (alpha and beta) based on their reactions to norepinephrine
and epinephrine, on cellular effects of receptor activation, and on relative affinities
and reactions to synthetic blocking or stimulating agents. Alpha-adrenergic receptors
respond to blocking agents such as phenoxybenzamine and phentolamine. When coupled
to adenylate cyclase through Gi protein, Alpha Adrenergic Receptor stimulation results
in decreased intracellular cyclic AMP.;