Alpha-receptor Definition

A receptor, found on the surface of some cells of the sympathetic nervous system, that is stimulated by adrenergic substances resulting in constriction of blood vessels and contraction of most smooth muscle.

A site in the autonomic nervous system in which excitatory responses occur when adrenergic agents, such as norepinephrine and epinephrine, are released. Activation of alpha-receptors causes various physiological reactions, including the stimulation of associated muscles and the constriction of blood vessels.