Adrenergic Receptor Subclassifications

Since there are two primary neurotransmitters involved in autonomic discharge, there are two primary classifications of postsynaptic receptors. Cholinergic receptors are located at acetylcholine synapses, and adrenergic receptors are located at norepinephrine synapses. As indicated in Figure 18-2, each type of receptor has several subclassifications. The location and functional significance of these classifications and subclassifications are presented here. 

The subclassification of the a-adrenergic receptor (a-AR) into the a,- and Oj-subtypes [1,2] made possible the development of effective antihypertensive drugs that either selectively block the Oj-AR or activate the Oj-subtype. 

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