AJP - Regulatory, Integrative and Comparative Physiology, Vol 264, Issue 3 630-R637, Copyright © 1993 by American Physiological Society
Gastric branch vagotomy blocks nutrient and cholecystokinin-induced suppression of gastric emptying
G. J. Schwartz, G. Berkow, P. R. McHugh and T. H. Moran
Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205.
A role for the vagus nerve in the emptying of intragastric nutrients and
the gastric inhibitory actions of the brain-gut peptide cholecystokinin
(CCK) has been proposed. To directly assess the role of the gastric vagal
branches in these actions, we compared the emptying of 5-ml nutrient and
nonnutrient gastric loads in male rats in which both branches of the
gastric vagus nerves were cut (GVX, n = 7) with emptying in surgical
control (n = 8) rats. Gastric emptying of saline was also examined in both
groups after intraperitoneal administration of 8 micrograms/kg CCK. In
control rats, high osmolarity, low pH, and caloric density all
significantly decreased gastric emptying compared with the emptying of
physiological saline. In addition, fat (oleic acid) and protein (peptone)
loads emptied significantly more slowly than isocaloric carbohydrate
(glucose) loads. Gastric branch vagotomy completely blocked the suppression
of emptying produced by fat, protein, carbohydrate, and acid loads. In
addition, GVX attenuated the ability of hyperosmotic nutrient and
nonnutrient loads to inhibit emptying to the same degree, irrespective of
their caloric content. Finally, in intact rats, CCK significantly inhibited
the emptying of physiological saline, and gastric vagotomy abolished this
suppression. Taken together, these results are consistent with the
proposals that 1) the controlled emptying of caloric, hyperosmotic, and
acidic solutions is dependent on gastric vagal branches, and 2) exogenous
CCK relies on an intact vagal pathway in the control of gastric emptying.
