TRH microinjection into DVC enhances motility of rabbits gallbladder via vagus nerve.

AIM: To investigate the effects of TRH in DVC on motility of the gallbladder in rabbits. METHODS: fter fasted for 15h-18h, rabbits were anesthetized with urethane (1.0 g/kg). Gall-bladder pressure (GP) was measured by a frog bladder perfused with normal saline. RESULTS: After microinjection of TRH (8.8 nmol, 1 μL) into DVC, GP was raised and the frequency of phasic contraction of gallbladder (FPCGB) increased. All the doses of TRH (0.13, 0.25, 0.50, 0.80, 1.30 nmol, 1 μL) injected into DVC could excite the motility of gallblader. As the dose of TRH was enlarged, the amplitude and duration of the reaction increased. Effects of TRH in DVC on motility of the gallbladder could be completely abolished by atropine (0.2 mg/g, i.v.) or vagotomy, but could not be inhibited by phentolamine iv (1.5 mg/g) or propranolol iv (1.5 mg/g)or by transecting the spinal cord. CONCLUSION: Thyrotropin-releasing hormone in DVC can excite motility of gallbladder. This effect was mediated by vagus nerves and peripheral M receptor. Its physiological significance may be related to maintaining the phasic contraction of gallbladder in interdigestive period.