Involvement of the medial preoptic area in the anorectic action of
estrogens.
Dagnault, Anne, and Denis Richard.
D[acute]epartement de Physiologie, Facult[acute]e de
M[acute]edecine, Universit[acute]e Laval, Qu[acute]ebec (Qu[acute]e),
G1K 7P4, CANADA
APStracts 3:0295R, 1996.
The implication of the medial preoptic area (MPOA) as a site for
estrogen in the regulation of energy balance was investigated.
Measurements of food intake, oxygen consumption (VO2) and carbon
dioxide production (VCO2) were performed in ovariectomized rats
injected with estradiol (E2) in the medial preoptic nucleus (MPN).
Moreover, knowing the potential for corticotropin-releasing factor
(CRF) in the anorectic effects of estrogens, we identified estrogen
receptors (ER) colocalised in CRF-containing cells of the MPOA, and
how MPN injections of CRF compared to estrogen injections with
respect to VO2 and the VO2/VCO2 ratio (respiratory quotient, RQ).
These energy balance measurements following the injections of four
different doses of either E2 or CRF were carried out in meal-fed rats
chronically implanted with a guide-cannula targeted to the MPN. The
identification of cells colocalizing ER and CRF was determined using
a double-immunostaining procedure revealing ER and CRF
immunoreactivities with two different couplers. The injection of E2
into the MPN induced a dose-dependent reduction in food intake,
whereas it did not affect VO2 nor RQ. Conversely, the injection of
CRF in the MPN had no effect on food intake, but increased VO2 and
decreased RQ. The colocalization of ER and CRF immunoreactivities was
found in the MPOA and adjacent regions of the bed nucleus of the
stria terminalis. In conclusion, the results of this study provide
evidence that the MPOA may represent a potential site for the
anorectic effects of E2. Furthermore, the presence of ER and CRF in
neurons of the MPOA and adjacent areas suggests a direct interaction
between estrogens and the CRF system in the MPOA which is consistent
with a role for CRF in the anorectic effects of estrogens. Finally,
the results of this study indicate that the effects of a CRF
injection in the MPOA differ from those of estrogens suggesting that,
if CRF neurons are involved in the anorectic effect of estrogens,
they likely exert their action outside the MPOA.
Received 1 March 1996; accepted in final form 1 July 1996.
APS Manuscript Number R129-6.
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