EFFECT OF NEUROTENSIN ON THE CANINE GALLBLADDER MOTILITY - IN-VIVO AND IN-VITRO EXPERIMENTS

Neurotensin (NT) (10(-8)-10(-6)) exerted a dose-dependent increase in the tone and release of [H-3]ACh in the guinea-pig gallbladder muscle strips but was inefficient in the canine gallbladder muscle strips. Ho wever, in conscious dogs NT (2.5-20 ng/kg intravenously (i.v.)) dose-d ependently increased the gallbladder pressure. Similar was the effect of CCK8 (1-10 ng/kg i.v.) and carbachol (0.5-2 mug/kg i.v.). The NT- o r CCK8-induced gallbladder pressure was inhibited by atropine (10-50 m ug/kg i.v.) or hexamethonium (0.5-3 mg/kg i.v.). Somatostatin (1-2 mug /kg i.v.) or VIP (0.5-1 mug/kg i.v.) also reduced or even abolished th e NT- or CCK8-induced gallbladder pressure. The NT-induced increase of the tone of guinea-pig gallbladder preparations was accompanied by an increase of [H-3]ACh release, suggesting the involvement of cholinerg ic innervation.