General Organization and Functions of Adrenergic Nerves

Abstract

The term’ sympathetic’ was originally used for all visceral nerves, but Gaskell (1886) showed that there were gaps in the autonomic outflow in the cranial and sacral regions, and in 1905, Langley demonstrated that the cranial and sacral outflows were pharmacologically different from the thoracolumbar (sympathetic) system. In his classical book, Langley (1921) considered the autonomic nervous system to be composed of two main subsystems, the sympathetic and the parasympathetic, and he regarded the enteric system to be separate from these. Both the sympathetic and parasympathetic efferent pathways are composed of a chain of at least two neurons, a preganglionic neuron which is located in the neuraxis and a postganglionic neuron which is located in a peripheral ganglion. The preganglionic neurons of both parasympathetic and sympathetic systems are cholinergic (see Dale, 1937). The postganglionic parasympathetic neurons are mainly cholinergic, while the postganglionic sympathetic neurons are mainly adrenergic (see Bacq, 1934; von Euler, 1956; Campbell, 1970). In the enteric system, cell bodies of cholinergic neurons, sensory neurons and non-adrenergic, non-cholinergic inhibitory (purinergic) neurons appear to be present, but with few exceptions, no cell bodies of adrenergic neurons (see Burnstock, 1969, 1972; Burnstock & Costa, 1973; Furness & Costa, 1974).