The Role of Presynaptic Receptors in the Modulation of Neurotransmission

Abstract

The calcium dependent release of neurotransmitter from nerves in response to appropriate stimuli is modulated by a number of presynaptic receptors. In the sympathetic nervous system receptors for α-agonists, dopamine, adenosine, opiates, cholinergic muscarinic and prostaglandins of the E series inhibit the release of noradrenaline. In contrast, β-adrenoceptor agonists, angiotensin II and nicotine facilitate release of the neurotransmitter. This article considers the presynaptic dopamine, α2- and β-adrenoceptors, three receptors which are either realised or potential therapeutic targets for drug action. To date the pharmacological and physiological investigations of the roles of these receptors has been hampered by the lack of sufficiently selective antagonists for each receptor. However, new compounds are now being produced with much greater selectivity than has been attained before. It is hoped that these compounds will make it possible to define more clearly the role of these presynaptic receptors in the modulation of transmitter release.