CEREBRAL BLOOD-FLOW AND METABOLISM IN DOGS WITH CHRONIC DIABETES

Background: Previously, the authors found than anesthetized diabetic d ogs had increased cerebral blood flow (CBF) and oxygen consumption (CM RO2). These results may have been influenced by anesthesia or surgery. The aim of this study was to determine whether CBF and CMRO2 are incr eased in the awake or anesthetized state in the absence of acute surgi cal stress in diabetic dogs. A second aim was to determine whether inc reased CBF and CMRO, in diabetic dogs are mediated through beta-adrene rgic mechanisms. Methods: Diabetic dogs (n = 8) underwent total surgic al pancreatectomy followed by 4 months of insulin management (16 +/- 0 .4 units/day, mean +/- SE) to maintain fasting and 3 PM blood glucose 10-17 mm. Control dogs (n = 8) underwent sham operation followed by a 4-month convalescence. Using previously inserted catheters, CBF (radio labelled microspheres) and CMRO2 (sagittal sinus sampling) were measur ed before and after propranolol (2 mg/kg) in both the awake and anesth etized states. Results. During the 4 months before CBF studies, the fa sting blood glucose was greater in diabetic group than in the control group (11.0 +/- 0.3 vs. 4.0 +/- 0.1 mm, respectively). No difference o ccurred between groups in CBF or CMRO2. In the awake state, propranolo l administration caused no CBF or CMRO, changes. However, during anest hesia with 50 mug/kg fentanyl plus 10 mg/kg pentobarbital, propranolol administration decreased CBF in control, but not in diabetic, dogs. C onclusions: The authors' previous results showing increased CBF and CM RO, with diabetes may be secondary to a differential response to acute surgical stress, a factor that was eliminated iii this study. These r esults indicate that diabetes is associated with changes in the beta-a drenergic system that become evident under fentanyl/pentobarbital anes thesia.