title: Brainstem dysfunction is provoked by a less pronounced hypoglycemic stimulus in diabetic BB rats.
abstract: Recent studies suggest that moderate hypoglycemia impairs brainstem function in normal humans and rats. To examine whether diabetes alters this response, simultaneous auditory-evoked potentials were recorded directly from the inferior colliculus (IC) and from the brainstem before and after controlled hypoglycemia (clamp) in awake insulin-dependent diabetic BB/Wor rats. Hyperglycemic diabetic animals were studied either during hyperinsulinemic euglycemia (5.6 mmol/l, n = 4) or mild hypoglycemia (3.5 mmol/l, n = 9). Nondiabetic controls were also studied at 3.5 mmol/l (n = 7) and at 2.8 mmol/l (n = 6). Brainstem function was not affected during euglycemia in diabetic rats. However, when plasma glucose was lowered to 3.5 mmol/l, the diabetic rats showed a 10% delay in IC evoked potential (ICEP) latency, whereas nondiabetic animals did not. This occurred despite similar counterregulatory hormones in both groups. The brainstem auditory-evoked potential (BAEP) localized the defect in the diabetic group to an area in or near the IC. When glucose levels were lowered to 2.8 mmol/l, however, brain function was impaired in nondiabetic rats as well. Again the defect was restricted to an area in or near the IC. We conclude that mild hypoglycemia causes a functional impairment in the IC region of the brainstem in both nondiabetic and diabetic rats. However, in the diabetic rats, this alteration occurs after a less pronounced hypoglycemic stimulus. Our findings suggest that chronic hyperglycemia leads to metabolic adaptions that render the diabetic brain more susceptible to mild hypoglycemia.
authors.affiliation: Yale University School of Medicine, Department of Internal Medicine/Endocrinology, New Haven, CT 06510, USA.
authors.forename: R J
authors.initials: RJ
authors.lastname: Jacob
authors.forename: A B
authors.initials: AB
authors.lastname: Weber
authors.forename: J
authors.initials: J
authors.lastname: Dziura
authors.forename: J
authors.initials: J
authors.lastname: Morgen
authors.forename: R S
authors.initials: RS
authors.lastname: Sherwin
mesh_terms: D000818:Animals; D001933:Brain Stem / Q000502:physiology / Q000503:physiopathology*; D003922:Diabetes Mellitus, Type 1 / Q000097:blood / Q000503:physiopathology*; D004837:Epinephrine / Q000097:blood; D005072:Evoked Potentials, Auditory; D005934:Glucagon / Q000097:blood; D006442:Glycated Hemoglobin / Q000032:analysis; D006801:Humans; D007003:Hypoglycemia / Q000503:physiopathology*; D007245:Inferior Colliculi / Q000502:physiology / Q000503:physiopathology*; D007328:Insulin / Q000097:blood; D008297:Male; D009638:Norepinephrine / Q000097:blood; D051381:Rats; D011913:Rats, Inbred BB; D012016:Reference Values; D013997:Time Factors
chemical_list: D004837:Epinephrine; D005934:Glucagon; D006442:Glycated Hemoglobin; D007328:Insulin; D009638:Norepinephrine