Effects of recurrent antecedent hypoglycaemia and chronic hyperglycaemia on brainstem extra-cellular glucose concentrations during acute hypoglycaemia in conscious diabetic BB rats.
OBJECTIVE
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.


CONCLUSIONS
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.
McCrimmon
R J
RJ
Department of Internal Medicine and Endocrinology, Yale University School of Medicine, P.O. Box 208020, New Haven CT 06520-8020, USA.
Jacob
R J
RJ
Fan
X
X
McNay
E C
EC
Sherwin
R S
RS
D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D001812:Blood-Brain Barrier; D001933:Brain Stem / Q000378:metabolism*; D003922:Diabetes Mellitus, Type 1 / Q000097:blood / Q000235:genetics / Q000378:metabolism*; D045604:Extracellular Fluid / Q000378:metabolism; D005947:Glucose / Q000378:metabolism*; D006943:Hyperglycemia / Q000503:physiopathology*; D007003:Hypoglycemia / Q000503:physiopathology*; D051381:Rats; D011913:Rats, Inbred BB
D001786:Blood Glucose; D005947:Glucose