Occurrence and effects on motility of bombesin related peptides in the gastrointestinal tract of the Atlantic cod, Gadus morhua.

1. Low levels of bombesin-like immunoreactivity (less than 1.10 pmol/g tissue), eluting at the same position as synthetic bombesin and litorin, have been measured in muscle and mucosa of the gastrointestinal canal of the cod, Gadus morhua. 2. Immunohistochemistry showed bombesin-like material in endocrine cells and nerves throughout the gut. Intensity and absorption controls indicated a difference in character between the peptides present in stomach and intestinal muscle respectively. 3. Stomach motility was stimulated by bombesin (pD2 = 8.27 +/- 0.19), litorin (8.03 +/- 0.04) and (less potently) GRP (less than 7.46 +/- 0.22). Litorin (8.21 +/- 0.31) had an inhibitory effect on intestinal motility. 4. In conclusion, one or several bombesin-like peptides may be involved in the control of gastrointestinal motility in the cod, causing opposite effects on stomach and intestine. The structure of the peptide in gastric nerves may differ from that in intestinal nerves.