Hypoglycemia-induced noradrenergic activation in the VMH is a result of decreased ambient glucose

During insulin-induced hypoglycemia, there is an increase in extracellular norepinephrine (NE) in the ventromedial hypothalamus (VMH). This brain area is known to play an important role in integrated hormonal and behavioral responses to systemic hypoglycemia. Selective glucoprivation restricted to t...

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Published inAmerican journal of physiology. Regulatory, integrative and comparative physiology Vol. 58; no. 4; pp. R977 - R981
Main Authors DE VRIES, Martin G, LAWSON, Marcus A, BEVERLY, J. Lee
Format Journal Article
LanguageEnglish
Published Bethesda, MD American Physiological Society 01.10.2005
Subjects
Biological and medical sciences
Brain
Carbohydrates
Feeding. Feeding behavior
Fundamental and applied biological sciences. Psychology
Glucose
Hormones
Hypoglycemia
Insulin
Metabolisms and neurohumoral controls
Vertebrates: anatomy and physiology, studies on body, several organs or systems
Pancreatic hormone
Rat
freely moving rats
Secretion
Rodentia
Central nervous system
Male
Activation
Glucose
Hypothalamus
Catecholamine
Extracellular
Insulin
extracellular fluids
Encephalon
Vertebrata
glucosensing neurons
Mammalia
Induced hypoglycemia
Norepinephrine
Behavior
in vivo microdialysis
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Summary:During insulin-induced hypoglycemia, there is an increase in extracellular norepinephrine (NE) in the ventromedial hypothalamus (VMH). This brain area is known to play an important role in integrated hormonal and behavioral responses to systemic hypoglycemia. Selective glucoprivation restricted to the VMH is both necessary and sufficient to initiate secretion of counterregulatory hormones. The present study was designed to investigate whether increased release of NE in the VMH depends on detection of glucoprivation localized in this area. In awake, chronically catheterized male Sprague-Dawley rats, extracellular NE in the VMH was monitored using 1-mm microdialysis probes perfused with Krebs Ringer buffer (KRB) or KRB + 100 mM D-glucose (D-Glc). During insulin-induced hypoglycemia (glycemic nadir ~2.4 mM) extracellular NE was increased to >160% of baseline (P < 0.01) only in the KRB + insulin group. There was no increase in NE from baseline when glucose was added to the perfusate to maintain euglycemia at the periprobe environment. The sympathoadrenal response to hypoglycemia, present in the KRB + insulin group, was attenuated in the D-Glc + insulin group. The present results confirm that noradrenergic activation in the VMH during systemic hypoglycemia depends on detection of glucoprivation locally in this area. These data provide additional support for the importance of increased noradrenergic activity in the VMH in the counterregulatory hormonal responses to hypoglycemia.[PUBLICATION ABSTRACT]
ISSN:0363-6119
1522-1490