Actions of galanin fragments on rat, guinea-pig, and canine intestinal motility.

The 1-20 fragment of synthetic porcine galanin, prepared by tryptic digestion of the intact molecule, was equipotent to synthetic porcine galanin 1-29 in the smooth muscle actions of exciting the rat jejunal longitudinal muscle in vitro and inhibiting circular muscle contractions of the canine small intestine in vitro and in vivo, but was less potent in inhibiting nerve-stimulated contractions of the guinea-pig taenia coli. Fragment 21-29 was effective at high doses only in the canine ileum. Activity of galanin 1-11 was greatly reduced in the dog in vivo. These results may reflect species or cell type differences.