ABSTRACT
The digestive tract is conspicuously rich in local neurons, collectively referred to as the enteric nervous system. Processes such as absorption, secretion and coordinated peristaltic activity are to a great extent regulated by intramural nerve reflexes. The collections of nerve cell bodies that constitute the myenteric ganglia are situated between the outer and inner smooth muscle layers. The ganglia and the interconnecting nerve strands form a continuous meshwork with the nerve cell bodies accumulated at the nodes. The neurons in the gut can be classified ultrastructurally by the appearance of the vesicles present in the terminals. The different vesicular populations have been described as small clear vesicles, small granular vesicles, large granular vesicles, large opaque vesicles, flattened vesicles, or ring vesicles. The chapter reviews the distribution, origin, projection patterns and chemical coding of a variety of peptide-containing enteric neurons. Neurotensin is a 13-amino-acid peptide originally isolated from bovine hypothalamus. Later it was also demonstrated in human and bovine intestine.
