Noradrenergic and GABAergic systems in the medial hypothalamus are activated
during hypoglycemia.
Beverly, J. Lee, Martin G. De Vries, Stephan D. Bouman, and Linda M. Arseneau.
1Department of Animal Sciences, 2Division of Nutritional Sciences, and 3Program in
Neuroscience, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801; and
4Department of Animal Physiology, University of Groningen, 9750 AA Haren, The
Netherlands
APStracts 7:0432R, 2000.
Noradrenergic and GABAergic systems in the medial hypothalamus influence plasma
glucose and may be activated during glucoprivation. Microdialysis probes were placed
into the ventromedial nucleus (VMH), lateral hypothalamus (LHA), and paraventricular
nucleus (PVH) of male Sprague-Dawley rats to monitor extracellular concentrations of
norepinephrine (NE) and GABA. During systemic hypoglycemia, induced by insulin (1.0
U/kg), NE concentrations increased in the VMH (P < 0.05) and PVH (P = 0.06) in a
bimodal fashion during the first 10 min and 20-30 min after insulin administration. In the
VMH, GABA concentrations increased (P < 0.05) in a similar manner as NE.
Extracellular NE concentrations in the LHA were slightly lower (P = 0.13), and GABA
levels remained at baseline. The increases in NE and GABA in the VMH were absent
during euglycemic clamp; however, NE in the PVH still increased, reflecting a direct
response to hyperinsulinemia. On the basis of these data we propose that the activity of
noradrenergic afferents to the medial hypothalamus are increased during hypoglycemia
and influence the activity of local GABAergic systems to activate appropriate
physiological compensatory mechanisms.
Received 22 June 2000; accepted in final form 9 October 2000
APS Manuscript Number R395-0.
Article publication pending Am J Physiol Regulatory Integrative Comp Physiol
ISSN 1080-4757 Copyright 2000 The American Physiological Society.
Published in APStracts on 30 November 2000