Gastric volume detection after selective vagotomies in rats.
Phillips, Robert J., and Terry L. Powley.
Department of Psychological Sciences, Purdue University, West
Lafayette, IN 47907
APStracts 5:0080R, 1998.
Rats receiving intragastric infusions of 2.5, 5.0, 7.5, or 10.0 ml of
normal saline, while their pylori are reversibly occluded, suppress
meal size to the smallest infusion and display a dose-dependent
reduction across volumes (Phillips, R.J., and T.L. Powley, Am. J.
Physiol., 271: R766-R779, 1996). To evaluate the contributions of the
vagus to this detection of gastric volume, groups prepared with
different selective vagotomies and equipped with pyloric cuffs and
gastric catheters were tested. Liquid diet consumption during a 30
-min feeding bout was measured after infusions of 5.0 and 10.0 ml of
normal saline on cuff-open and cuff-closed trials. Consistent with
earlier observations, sham animals with cuffs closed exhibited
volume-dependent suppression of food intake to the infusions, and
completely vagotomized animals did not inhibit feeding in response to
the loads. In cuff-closed trials, the suppression function slopes of
the selective vagotomy groups were intermediate to those of the shams
and the completely vagotomized animals. Furthermore, for the
different groups, the extent of suppression after vagotomy was
proportional to the density of the afferent innervation respective
branches supplied to the stomach. Specifically, the group with the
gastric branches spared (nonsignificantly attenuated in comparison to
shams) and the group with only the hepatic branch spared
(significantly attenuated with respect to shams) both still exhibited
significant dose-dependent suppression slopes (compared to
completes), whereas the group with only celiac branches spared was
not significantly different than completely vagotomized animals. In
sum, the vagus nerve mediates the detection of the gastric volumes
tested, and the different branches of the vagus make distinctive
contributions to this afferent feedback.
Received 26 September 1997; accepted in final form 24 February
1998.
APS Manuscript Number R622-7.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1998 The American Physiological Society.
Published in APStracts on 9 March 1998