Capsaicin attenuates feeding suppression but not reinforcement by
intestinal nutrients.
Lucas, Fran[cedilla]cois, and Anthony Sclafani.
Department of Psychology, Brooklyn College and the Graduate School,
The City University of New York, Brooklyn, NY 11210
APStracts 2:0332R, 1995.
Lucas F. & Sclafani, A. Capsaicin attenuates feeding suppression
but not reinforcement produced by intestinal nutrients. During and
after a meal, the presence of nutrients in the intestine can be
rapidly detected and signalled to the brain via visceral afferents.
Intestinal infusions of carbohydrate and fat suppress food intake and
this satiety action is inhibited by capsaicin, a neurotoxin that
produces a partial visceral deafferentation. This study determined if
the postingestive reinforcing action of nutrients is also suppressed
by capsaicin treatment. Food- restricted control and capsaicin
-treated rats were trained to drink a flavored solution paired with
intraduodenal (ID) infusions of carbohydrate (Polycose solution) on
some days and, on other days, a differently flavored solution paired
with ID water infusions. In a choice test, both groups displayed a
strong preference for the Polycose-paired flavor. In a subsequent
satiety test, however, ID Polycose suppressed sucrose sham-feeding in
the controls but not in capsaicin-treated rats. The same rats were
next trained to associate new flavors with ID fat (corn oil emulsion)
and ID water infusions. During training, oil infusions reduced oral
intakes in the controls much more than in the capsaicin treated rats.
Both groups reliably preferred the oil-paired flavor in the
subsequent choice test. These results indicate that, unlike the
satiating effect of intestinal carbohydrate and fat, the reinforcing
actions of these nutrients are not mediated by capsaicin-sensitive
visceral afferents. The data also imply that the postingestive
reinforcement produced by nutrients is not dependent upon the
nutrients' satiating quality.
Received 10 July 1995; accepted in final form 20 November 1995
APS Manuscript Number R428-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 8 December 95