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Abstract
Effects of glucagon-like peptide-1 (GLP-1) and glucagon on fasted gut motility in
conscious rats were investigated as regards dependence on nitric oxide (NO). Small
bowel motility was studied by electromyography and a jugular vein catheter was implanted
for administration of drugs. GLP-1 (5-40 pmol x kg(-1) x min(-1)) prolonged the cycle
length and abolished phase III of the migrating myoelectric complex (MMC) (P<0.01).
Low doses of GLP-1 did not affect duration, propagation velocity or calculated length
of phase III. At 1 mg x kg(-1) N(omega)-nitro-L-arginine (L-NNA) blocked the GLP-1
response up to a dose of 10 pmol x kg(-1) x min(-1) (P<0.05), while higher doses were
able to overcome L-NNA-induced disinhibition of the GLP-1 response (P<0.05). Similarly,
L-arginine at 300 mg x kg(-1) prevented L-NNA-induced disinhibition of the GLP-1 response
(P<0.05). Glucagon (200-1000 pmol x kg(-1) x min(-1)) prolonged the cycle length and
abolished phase III of MMC (P<0.01) independent of NO. Again, low doses of glucagon
did not affect duration, propagation velocity or calculated length of phase III. In
conclusion, inhibition of fasted motility by GLP-1 at low doses is dependent on NO,
while high doses of GLP-1 and glucagon exert effects on motility independently from
NO.