Role of the autonomic nervous system in the thermogenic response to
food in lean individuals.
Jonge, Lilian De, and Dominique R. Garrel.
Department of Nutrition, University of Montreal Medical School, and
H[circumflex]otel-Dieu Hospital, Montr[acute]eal, Qu[acute]ebec,
Canada
APStracts 4:0010E, 1997.
The aim of this study was to determine the role of the autonomic
nervous system (ANS) in obligatory and facultative components of the
thermogenic response to food (TRF). Nineteen lean, healthy subjects
participated in this study which comprised two protocols, each
exploring one component of the ANS. In the first experimental group,
propranolol (Prime: 80[mu]g/kg; continuous: 1 [mu]g/kg/min) was
infused intravenously to inhibit sympathetic nervous activity (SNA),
while in the second, atropine (Prime: 5 [mu]g/kg; continuous: 5
[mu]g/kg/min) was used to inhibit parasympathetic nervous activity
(PNA). The thermogenic response to food was measured on 4 occasions:
1) after oral ingestion of a breakfast, during 0.9% NaCl perfusion,
2) after oral ingestion of the same breakfast during the perfusion of
one of the drugs, 3) after intragastric injection of the same,
blenderized meal as in 1) during 0.9% NaCl perfusion, and 4) after
intragastric feeding during the administration of one of the drugs.
Energy expenditure was measured by indirect calorimetry for 30
minutes before, and 6 hours after, ingestion of the meal. Facultative
TRF was defined as the difference between oral and intragastric TRF.
Intragastric feeding significantly reduced TRF in both studies:
6.6+/- 1.0% vs 8.7+/-0.8% of the ingested energy in the SNA study and
5.5+/-1.6% vs 7.4%+/-3.1% in the PNA study. During propranolol
infusion, TRF was significantly lower than during saline infusion
after oral feeding: (6.9+/-1.0 % vs 8.7+/-0.8% of ingested energy),
but not after intragastric feeding. During atropine administration,
TRF was reduced after both oral and intragastric feeding, although
statistical significance was not reached in the latter. Atropine
administration decreased gastric emptying (measured with an isotopic
method) 2h post ingestion by 50%. These results show that the SNA is
necessary for the facultative component of TRF to occur in man. The
role of the PNA appears to be related to its action on gastric
emptying.
Received 20 August 1996; accepted in final form 27 December 1997.
APS Manuscript Number E406-6.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 19 February 1997