Adrenoceptors

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These are receptors for both NORADRENALINE (NOREPINEPHRINE) and ADRENALINE (EPINEPHRINE). They are found in the CENTRAL NERVOUS SYSTEM and on a variety of tissues innervated by the PERIPHERAL NERVOUS SYSTEM. All the various subtypes of adrenoceptor are coupled to G PROTEINS. Adrenoceptors are discriminated broadly into two types: ALPHA RECEPTORS (α receptors) and BETA RECEPTORS (β receptors). Alpha receptors tend to be found in the CENTRAL NERVOUS SYSTEM, beta receptors in the rest of the body, though this dissociation is by no means absolute. Both types, alpha and beta, are divided into sub-classes.

The table on page 18 shows the sub-classes of adrenoceptor, the relative potency of noradrenaline and adrenaline, and the main locations of the receptors. Note also that it was once thought that alpha-2 receptors had an exclusively PRESYNAPTIC location. This is not longer thought to be the case. Adrenoceptors of all sorts can be found at both pre- and POSTSYNAPTIC sites, and may act as AUTORECEPTORS.

The following table (on page 19) indicates some of the drugs that have been used as AGONISTS or ANTAGONISTS at adrenoceptors. Note that it is unusual to find a drug that has an action exclusively at one type of RECEPTOR: in most cases selectivity for a receptor subtype is relative. The agonists and antagonists listed here, unless otherwise specifically noted, show strong selectivity for the receptors indicated, though this selectivity may not necessarily be absolute.

Feldman R., Meyer J.S. & Quenzer L.F. (1997) Principles of Neuropsychopharmacology, Sinauer Press: Sunderland MA.

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