Drugs Affecting the Autonomic Nervous System and Motor End-Plate

Abstract

When considering the drugs which affect the autonomic nervous system and motor end-plate, it is useful to think in terms of four basic kinds of neuronal connection between the central nervous system and the end-organ. These are displayed diagramatically below. The chemical transmitter at the first synapse in each case is acetylcholine. All these sites are ‘nicotinic’ as the effects of transmission can be mimicked by nicotine-like substances. The second synapse in the parasympathetic pathway is rather different and although dependent on acetylcholine as transmitter it is also stimulated by muscarine-like substances. In the sympathetic pathway adrenaline and noradrenaline are the second synapse transmitter and the various end-organ receptors have been classified into α and β chiefly according to whether their effect is an excitatory or inhibitory one. This classification has proved useful but has required a little modification [1]. For further discussion of this subject see references [2] and [3].