Gastroenterology
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The central action of peptides to influence GI motility in experimental animals is summarized in Table 1. TRH stimulates gastric, intestinal, and colonic contractility in rats and in several experimental species. A number of peptides including calcitonin, CGRP, neurotensin, NPY, and mu opioid peptides act centrally to induce a fasted MMC pattern of intestinal motility in fed animals while GRF and substance P shorten its duration. ⋯ The neural pathways from the brain to the gut whereby these peptides express their stimulatory or inhibitory effects on GI transit is vagal dependent with the exception of calcitonin. It is not known whether the vagally mediated inhibition of GI transit by these peptides results from a decrease activity of vagal preganglionic fibers synapsing with excitatory myenteric neurons or an activation of vagal preganglionic neurons synapsing with inhibitory myenteric neurons. The lack of specific antagonists for these peptides has hampered the assessment of their physiological role.(ABSTRACT TRUNCATED AT 400 WORDS)