- Adrenergic Receptors bind norepinephrine and epinephrine, chemicals originally termed "adrenalin" by the British. They are found in both the CNS and Autonomic Nervous System where they direct a wide variety of cognitive and physiological functions. Four basic subtypes exist which display distinct physiological functions and tissue expression.
- Early pharmacological experiments demonstrated two basic subclasses of adrenergic receptors: alpha and beta. Further studies have shown that the majority of the physiological effects of adrenergic receptors are carried out by four basic subtypes: Alpha1 Receptor, Alpha2 Receptor, Beta1 Receptor, and Beta2 Receptor.
- These subtypes display tissue-specific expression and generate distinct physiological effects when activated. Specific pharmacological agonists and antagonists for these subtype are in frequent clinical use and an intimate knowledge of their physiological functions is critical. This is discussed in further detail within each receptor subpage.
- All adrenergic receptors are G-protein coupled receptors; however, different subtypes are connected to different signaling systems, each of which is discussed in further detail on the receptor subpage. In general, alpha1 and beta receptors are excitatory with alpha1 receptors connected to Gq and beta receptors connected to Gs. In contrast, alpha2 receptors are inhibitory and are connected to Gi.
- Adrenergic Receptors are found in the CNS where they are critical for wakefulness, cognition, and mood. Within the autonomic nervous system, they are primarily found in the target organs innervated by the sympathetic nervous system and are the primary effectors of sympathetic outflow.