Peptidergic nerves.

In recent years the autonomic nervous system has been shown to consist of nerves containing a number of different neurotransmitter substances; a system far more complex than was originally thought. It has been demonstrated that a large part of the autonomic nervous system contains peptides, and that, in the gut, these nerves form a major complex that infiltrates the entire length and breadth of the tract. The detailed study of this peptidergic system has been facilitated by the development of specialised immunocytochemical methods, which have yielded information on the distribution and morphology of the various types of nerve. Thus, the distribution of these nerves can often be seen to parallel what is known about the actions of individual peptides. The majority of peptidergic nerves are intrinsic to the gut, forming, with the other intrinsic nerves, what appears to be a largely autonomous unit. This enteric system can be visualised as a "minibrain", under the general influence of the central nervous system but able to function, to a certain extent, by itself. The consequences of a breakdown in the normal functioning of this system can be seen in a number of gut diseases.