Intake suppression following hepatic-portal glucose infusion: all
-or-none effect and its temporal threshold.
Baird, John-Paul, Harvey J. Grill, Joel M. Kaplan.
Department of Psychology, University of Pennsylvania
APStracts 3:0365R, 1996.
The effects of hepatic-portal infusions of isotonic glucose on glucose
intake (3.2%) were evaluated with the intraoral intake test which,
unlike traditional tests, permits delivery of portal infusions in
explicit temporal relation to intake onset in non-deprived rats.
Continuous or discontinuous portal infusions (0.1 ml/min) of isotonic
glucose or saline were initiated 0, 30, 60 or 120 min before meal
onset. Jugular infusions of isotonic saline or glucose, and portal
infusions of isotonic saline, were without effect. For all effective
portal glucose infusions, intake was suppressed by about 30% of
baseline values. Insofar as the duration (and quantity) of effective
portal glucose infusions varied by a factor of ten, we conclude that
intraoral intake suppression under these conditions is all-or-none in
nature. Whether or not an intake suppression was obtained depended
more on when the infusion was delivered than on how much was infused.
Thus, 1.5 ml of isotonic glucose infused between 60 and 45 min prior
to the intake test was effective whereas 3.0 ml infused for the 30
min before intake was without effect. These results suggest that the
liver participates in the control of future intake but not in the
termination of an ongoing meal. The temporal requirement for intake
suppression should be considered in analyses of the metabolic,
hormonal and/or neural mechanisms that underlie the liver's
contribution to intake control.
Received 20 November 1995; accepted in final form 11 September
1996.
APS Manuscript Number R725-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 5 November 1996