Effects of lorglumide and atropine on MgSO4-induced gallbladder emptying in conscious dogs

The aim of the study was to examine the possible involvement of cholecystok inin (by lorglumide) and cholinergic mechanisms (by atropine) in magnesium sulphate (MgSO4)-induced gallbladder contraction of conscious dogs. The gal lbladder (GB) volume was determined by ultrasonography. The optimal dose of 80 mg kg(-1) of MgSO4 was determined from a MgSO4 dose-response curve usin g doses of 10, 20, 40, 80, 120 mg kg(-1). The largest dose of MgSO4 was les s effective than the optimal dose. Peak gallbladder contraction (32 per cen t) was achieved at 30 minutes. Atropine (50 mug kg(-1) s.c.) or lorglumide (1 mg kg(-1) p.o.) fully prevented Gs contraction. In conclusion, supraopti mal doses of MgSO4 have a diminishing effect. The sustained contraction of the gallbladder in response to the optimal dose of MgSO4 can be explained b y an additive effect of the cholecystokinin release and a cholinergic trigg er mechanism. Ultrasonography and MgSO4 stimulation proved to be a valuable technique for examination of gallbladder motility. (C) 2000 Harcourt Publi shers Ltd.