GASTRIN-RELEASING PEPTIDE STIMULATES POSSUM GALLBLADDER CONTRACTILITYIN-VITRO

Reports of the action of gastrin-releasing peptide (GRP) on gallbladde r contraction are limited to a few species. We compared the action of GRP, acetyl gastrin-releasing peptide 20-27 (GRP 20-27), and cholecyst okinin-octapeptide (CCK-8) on gallbladder contractility with and witho ut pretreatment with the neural inhibitor tetrodotoxin (TTX) and the b ombesin antagonist [D-Phr 6, Des-Met 14]-bombesin 6-14 ethylamide (BBS 6-14 E). Full-thickness muscle strips were prepared and suspended in organ baths. The maximum GRP, GRP 20-27, and CCK-8 responses were 54.2 +/- 4.2%, 74.6 +/- 6.4%. and 69.3 +/- 6.9% of that of carbachol, resp ectively. Pretreatment with TTX influenced the action of GRP 20-27, an d pretreatment with BBS 6-14 E influenced that of GRP and GRP 20-27. T hese studies show that GRP and GRP 20-27 are potent agonists of gallbl adder contractility, acting via GRP-preferring receptors, and that GRP 20-27 also acts via a neural component. (C) 1997 Elsevier Science Inc .