Dissociation of hypothalamic noradrenergic activity and sympathoadrenal responses to recurrent hypoglycemia

This study evaluated whether attenuation of sympathoadrenal responses to recurrent hypoglycemia is mediated by diminished noradrenergic activity in the hypothalamus. Male Sprague-Dawley rats received either once daily insulin (1.0 units/kg) injections or an equal administration of saline for 3 days....

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Published inAmerican journal of physiology. Regulatory, integrative and comparative physiology Vol. 55; no. 5; pp. R910 - R915
Main Authors DE VRIES, Martin G, LAWSON, Marcus A, BEVERLY, J. Lee
Format Journal Article
LanguageEnglish
Published Bethesda, MD American Physiological Society 01.05.2004
Subjects
Biological and medical sciences
Brain
Fundamental and applied biological sciences. Psychology
Hormones
Insulin
Motor control and motor pathways. Reflexes. Control centers of vegetative functions. Vestibular system and equilibration
Peripheral nervous system. Autonomic nervous system. Neuromuscular transmission. Ganglionic transmission. Electric organ
Rodents
Vertebrates: nervous system and sense organs
Pancreatic hormone
Rat
Rodentia
Central nervous system
ventromedial hypothalamus
Glucose
Hypothalamus
Paraventricular nucleus
Catecholamine
Metabolism
Sympathetic nervous system
Insulin
Encephalon
Blood plasma
Vertebrata
Mammalia
Induced hypoglycemia
microdialysis
Autonomic nervous system
Animal
Norepinephrine
rats
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Summary:This study evaluated whether attenuation of sympathoadrenal responses to recurrent hypoglycemia is mediated by diminished noradrenergic activity in the hypothalamus. Male Sprague-Dawley rats received either once daily insulin (1.0 units/kg) injections or an equal administration of saline for 3 days. Both groups received an administration of insulin on the fourth day, during which blood glucose and plasma catecholamines were determined, and extracellular norepinephrine (NE) in the ventromedial hypothalamus (VMH) or paraventricular hypothalamic nucleus (PVN) was monitored with microdialysis. The peak response of plasma epinephrine to insulin-induced hypoglycemia (nadir 3.2 mmol/l) was significantly reduced during the fourth hypoglycemic episode (774 +/- 134 pg/ml) compared with the first episode (2,561 +/- 410 pg/ml, P < 0.001). Baseline levels of extracellular NE were elevated 25% (P = 0.07) in the VMH and 46% (P = 0.03) in the PVN after multiple hypoglycemic episodes. There was no difference in noradrenergic activity during the first or fourth hypoglycemic episode in either brain area. The reduced sympathoadrenal output after recurrent hypoglycemia is likely postsynaptic from hypothalamic NE release or is mediated via a collateral pathway. [PUBLICATION ABSTRACT]
ISSN:0363-6119
1522-1490