Metabolic control of estrous cycles in syrian hamsters: i. central
versus peripheral neural signals mediating effects of
lipoprivation.
Schneider, Jill E.
Department of Biological Sciences, Lehigh University, Bethlehem,
Pennsylvania 18015
APStracts 3:0351R, 1996.
Metabolic control of estrous cycles in Syrian hamsters: I. Central
versus peripheral neural signals mediating effects of lipoprivation.
Am. J. Physiol., Metabolic energy availability has profound effects
on reproduction in a wide variety of species. We have been studying
the effects of fasting on estrous cycles in Syrian hamsters as a
model system for metabolic control of reproduction. In previous
experiments, a 48 h period of fasting inhibited estrous cycles in
lean, but not fat hamsters. In fat hamsters, the effects of fasting
may have been offset by the presence of high circulating levels of
free fatty acids mobilized from lipids in adipose tissue. Consistent
with this idea, fat hamsters treated with the inhibitor of fatty acid
oxidation, methyl palmoxirate (MP), showed fasting-induced anestrus.
Experiment 1 was designed to examine whether vagally-transmitted
signals are critical for the inhibitory effects of fasting and MP
treatment. Lean or fat hamsters that had received either bilateral,
subdiaphragmatic vagotomy or sham surgery were fasted and treated
with either MP or vehicle. In both vagotomized and sham-operated
hamsters, estrous cycles were inhibited in lean, fasted hamsters, and
in fat, fasted hamsters treated with MP, but not in fat, fasted
hamsters treated with vehicle. Thus, the results of experiment 1
indicated that vagally-transmitted signals about peripheral fatty
acid availability are not critical for the effects of these
particular metabolic challenges on estrous cycles in Syrian hamsters.
In experiment 2, hamsters without food were allowed to ingest pure
glucose or fructose solutions, or vegetable shortening. Half of each
group was treated with an inhibitor of glucose utilization, 2-deoxy
-D-glucose (2DG), or vehicle. If ingestion of fructose or shortening,
but not glucose, had protected hamsters from 2DG-induced anestrus,
this might have indicated that peripheral fuel availability is
critical for anestrus. To the contrary, 2DG treatment induced
anestrus regardless of the type of fuel ingested. Neither experiment
yielded results that implicated changes in peripheral fatty acid
oxidation as a critical signal in metabolic control of estrous
cycles.
Received 6 October 1995; accepted in final form 20 May 1996.
APS Manuscript Number R631-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 7 October 1996