TRH microinjection into DVC enhances motility of

Subject headings gallbladder; vagus nerve; dorsal vagal complex; thyrotropin releasing hormone; cholinergic M receptors; rabbits 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 (1.0g/kg). Gall-bladder pressure (GP) was measured by a frog blad-der perfused with normal saline. RESULTS After microinjection of TRH (8.8nmol, 1µl) 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, 1.30nmol, 1µl) injected into DVC could ex-cite the motility of gallblader. As the dose of TRH was enlarged, the amplitude and duration of the re-action increased. Effects of TRH in DVC on motility of the gallbladder could be completely abolished by atropine (0.2mg/g, i.v.) or vagotomy, but could not be inhibited by phentolamine iv (1.5mg/g) or propranolol iv (1.5mg/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 relat-ed to maintaining the phasic contraction of gallblad-der in interdigestive period