Stimulation of fluid intake by nutrients: oil is less effective
than carbohydrate.
Ramirez, Israel.
Monell Chemical Senses Center, Philadelphia, PA 19104-3308, Tel:
215 898-6896, FAX: 215-898-2084
APStracts 3:0296R, 1996.
It has been thought that the ability of nutrients to reinforce
ingestion is related to their ability to provide metabolizable
energy. This implies that the reinforcing effect of carbohydrate
should be similar to that of fat. To test this, rats were trained in
an apparatus that infused water or nutritive solutions/suspensions
into their stomachs every time that they drank a sapid solution. Each
training trial lasted one day. Successive training trials were
interspersed by one day periods in which the rats were infused with
plain water and offered either plain water or a tastant different
from the training taste (i.e. CS-). Three different sapid solutions
were used, a sweet solution (saccharin), a non-sweet solution (sodium
chloride), and a mixture of sweet and nonsweet. Starch or
maltodextrin infusions strongly and consistently stimulated intake of
these solutions. Oil infusions also significantly stimulated intake,
but feebly and less consistently. Indeed, in the one experiment in
which the only sapid fluid offered was saccharin, oil infusions had
no significant effect. Two different oil suspensions (one fine and
one coarse) were equally ineffective in stimulating saccharin intake.
In order to determine whether some unsuspected flaw in the infusion
experiments somehow produced invalid results, an additional
experiment was conducted in which rats ingested either starch or oil
suspensions by mouth. Consistent with the infusion experiments,
starch stimulated ingestion to a much greater degree than did oil. It
is concluded that intragastric infusion of triglyceride oil is a less
potent reinforcer of ingestion than is equicaloric infusion of
carbohydrate.
Received 27 December 1995; accepted in final form 9 July 1996.
APS Manuscript Number R821-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 21 August 1996