Effects of neurotensin on the motility of the isolated gallbladder, bile duct and ampulla in guinea-pigs.

Neurotensin induced dose-dependent contraction in the isolated gallbladder, bile duct and ampulla of guinea-pigs, which were usually reduced by atropine and tetrodotoxin. In all cases, the neurotensin-induced contraction of the gallbladder was reversed to relaxation by indomethacin after administration of atropine and tetrodotoxin. The neurotensin-induced contraction of bile duct and ampulla was reduced by indomethacin, atropine and tetrodotoxin, and was slightly enhanced in some experiments after guanethidine administration. Ganglion-, alpha- and beta-adrenoceptor, serotonin- and histamine-blocking agents did not affect the neurotensin-induced contraction in any of the preparations. These results suggest the following; (1) the contractile effects are due to excitement of cholinergic neurons in the myenteric plexus of the biliary tract, (2) the direct action of neurotensin on the smooth muscle of the bile duct and ampulla results in a small contraction, (3) the contraction in the gallbladder is partly caused by stimulation of prostaglandin synthesis.