Drug and neurotransmitter receptors. New perspectives with clinical relevance.

Our understanding of drug and neurotransmitter receptors has been greatly advanced by receptor binding techniques. The theme of multiple-receptor subtypes with clinical relevance is highlighted by calcium antagonist and benzodiazepine receptors. Numerous drugs may exert therapeutic and untoward effects via calcium channels. Examples include effects of loperamide hydrochloride on diarrhea, the phenothiazine thioridazine hydrochloride on cardiac and ejaculatory function, and the neuromuscular toxicity of aminoglycosides. Elevated numbers of calcium antagonist receptors in hypertrophic cardiomyopathy may be involved in the pathophysiology of this disease. Benzodiazepines act via discrete central and peripheral receptors. At central receptors, benzodiazepines facilitate the inhibitory effects of the neurotransmitter gamma-aminobutyric acid. Peripheral benzodiazepine receptors are localized to mitochondria and enriched in several endocrine glands where they are influenced by therapeutic blood levels of benzodiazepines such as diazepam.