title: Recurrent hypoglycemia is associated with loss of activation in rat brain cingulate cortex.
abstract: A subset of people with diabetes fail to mount defensive counterregulatory responses (CRR) to hypoglycemia. Although the mechanisms by which this occurs remain unclear, recurrent exposure to hypoglycemia may be an important etiological factor. We hypothesized that loss of CRR to recurrent exposure to hypoglycemia represents a type of stress desensitization, in which limbic brain circuitry involved in modulating stress responses might be implicated. Here, we compared activation of limbic brain regions associated with stress desensitization during acute hypoglycemia (AH) and recurrent hypoglycemia (RH). Healthy Sprague Dawley rats were exposed to either acute or recurrent 3-d hypoglycemia. We also examined whether changes in neuronal activation were caused directly by the CRR itself by infusing epinephrine, glucagon, and corticosterone without hypoglycemia. AH increased neuronal activity as quantified by c-fos immunoreactivity (FOS-IR) in the cingulate cortex and associated ectorhinal and perirhinal cortices but not in an adjacent control area (primary somatosensory cortex). FOS-IR was not observed after hormone infusion, suggesting that AH-associated activation was caused by hypoglycemia rather than by CRR. Importantly, AH FOS-IR activation was significantly blunted in rats exposed to RH. In conclusion, analogous with other models of stress habituation, activation in the cingulate cortex and associated brain areas is lost with exposure to RH. Our data support the hypothesis that limbic brain areas may be associated with the loss of CRR to RH in diabetes.
authors.affiliation: University of Cambridge Metabolic Research Laboratories/Department of Medicine/National Institute for Health Research Cambridge Biomedical Research Centre, Cambridge CB2 0QQ, United Kingdom.
authors.forename: Paul
authors.initials: P
authors.lastname: Hurst
authors.forename: Alastair S
authors.initials: AS
authors.lastname: Garfield
authors.forename: Claire
authors.initials: C
authors.lastname: Marrow
authors.forename: Lora K
authors.initials: LK
authors.lastname: Heisler
authors.forename: Mark L
authors.initials: ML
authors.lastname: Evans
mesh_terms: D000208:Acute Disease; D000818:Animals; D004195:Disease Models, Animal; D005947:Glucose / Q000378:metabolism*; D006179:Gyrus Cinguli / Q000187:drug effects / Q000378:metabolism* / Q000503:physiopathology*; D007003:Hypoglycemia / Q000453:epidemiology / Q000378:metabolism* / Q000503:physiopathology*; D015994:Incidence; D007328:Insulin / Q000494:pharmacology; D008297:Male; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012008:Recurrence; D013312:Stress, Physiological / Q000502:physiology
chemical_list: D007328:Insulin; D016760:Proto-Oncogene Proteins c-fos; D005947:Glucose