R J McCrimmon1, R J Jacob, X Fan, E C McNay, R S Sherwin. 1. Department of Internal Medicine and Endocrinology, Yale University School of Medicine, P.O. Box 208020, New Haven CT 06520-8020, USA.
Abstract
AIMS/HYPOTHESIS: Our aim was to determine whether the divergent effects of chronic exposure to hyperglycaemia or hypoglycaemia on the glycaemic threshold for auditory brainstem dysfunction are reflected in the extra-cellular fluid (ECF) concentrations of glucose in the inferior colliculus during hypoglycaemia in the diabetic BB rat. METHODS: Microdialysis was used to measure inferior colliculus ECF glucose concentrations under basal and hyperinsulinaemic (20 mU/kg.min) hypoglycaemic conditions. RESULTS: ECF glucose is increased under basal (hyperglycaemic) conditions and decreases during hypoglycaemia in both recurrently hypoglycaemic and chronically hyperglycaemic diabetic BB rats (to 0.5+/-0.1 and 0.8+/-0.2 mmol/L respectively), with no significant differences between groups. In both groups the plasma to ECF glucose ratio doubled during hypoglycaemia. CONCLUSION/ INTERPRETATION: Prior exposure to recurrent hypoglycaemia does not lead to increased ECF glucose concentrations in the inferior colliculus of diabetic BB rats. The resistance to impaired brainstem function seen in recurrently hypoglycaemic rats during hypoglycaemia cannot simply be attributed to increased blood-brain barrier glucose transport within this brain region.
AIMS/HYPOTHESIS: Our aim was to determine whether the divergent effects of chronic exposure to hyperglycaemia or hypoglycaemia on the glycaemic threshold for auditory brainstem dysfunction are reflected in the extra-cellular fluid (ECF) concentrations of glucose in the inferior colliculus during hypoglycaemia in the diabeticBBrat. METHODS: Microdialysis was used to measure inferior colliculus ECF glucose concentrations under basal and hyperinsulinaemic (20 mU/kg.min) hypoglycaemic conditions. RESULTS: ECF glucose is increased under basal (hyperglycaemic) conditions and decreases during hypoglycaemia in both recurrently hypoglycaemic and chronically hyperglycaemic diabeticBBrats (to 0.5+/-0.1 and 0.8+/-0.2 mmol/L respectively), with no significant differences between groups. In both groups the plasma to ECF glucose ratio doubled during hypoglycaemia. CONCLUSION/ INTERPRETATION: Prior exposure to recurrent hypoglycaemia does not lead to increased ECF glucose concentrations in the inferior colliculus of diabeticBBrats. The resistance to impaired brainstem function seen in recurrently hypoglycaemic rats during hypoglycaemia cannot simply be attributed to increased blood-brain barrier glucose transport within this brain region.
Authors: S A Segel; C G Fanelli; C S Dence; J Markham; T O Videen; D S Paramore; W J Powers; P E Cryer Journal: Diabetes Date: 2001-08 Impact factor: 9.461
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