Apolipoprotein A-IV acts in the brain to inhibit gastric emptying in the rat

We have very recently shown that intracisternal injection of apolipoprotein A-IV (apo A-IV), a glycoprotein produced in the small intestine by fat, dose-dependently inhibited gastric acid secretion in pylorus-ligated conscious rats. These results suggest that apo A-IV acts centrally as a neuromodulator to inhibit gastric secretion. The present study was carried out to examine the hypothesis that apo A-IV acts centrally to alter gastric emptying. Rats fasted 24 h received intracisternal injection of apo A-IV and a liquid meal by oral intubation under brief isoflurane anesthesia. Gastric emptying of a liquid meal was determined by the phenol red method. Intracisternal injection of apo A-IV inhibited gastric emptying of a liquid meal in a dose-dependent manner (1.0-4.0 micrograms). On the other hand, apo A-I in a dose of 4 micrograms failed to change gastric emptying. Gastric emptying was not altered by intraperitoneal administration of apo A-IV in a dose of 15 micrograms. These results suggest that apo A-IV acts centrally to delay gastric emptying of a liquid meal. Together with our recent finding that apo A-IV acts centrally to inhibit gastric acid secretion, the present study supports our hypothesis that apo A-IV may be involved in lipid-induced inhibition of gastric function.