AJP - Endocrinology and Metabolism, Vol 260, Issue 3 E440-E446, Copyright © 1991 by American Physiological Society
CNS stimulation does not affect hepatic venous glucose concentration in severely diabetic rats
H. Miura, A. Iguchi, K. Uemura, A. Yatomi, T. Tamagawa and N. Sakamoto
Third Department of Internal Medicine, Nagoya University School of Medicine, Japan.
To assess the role of the central nervous system (CNS) in carbohydrate
metabolism in diabetes, neostigmine was injected into the third cerebral
ventricle in fed rats with streptozotocin (STZ; 80 mg/kg)-induced diabetes
under pentobarbital sodium anesthesia. Changes in hepatic venous plasma
glucose concentrations were monitored. Neostigmine injection caused no
significant changes in the hepatic venous plasma glucose concentration in
untreated diabetic rats, whereas the glucose level increased significantly
in insulin-treated diabetic rats similarly to the changes in normal control
animals. In diabetic rats, the plasma levels of glucagon, epinephrine, and
norepinephrine were increased significantly by neostigmine. After various
doses (35-80 mg/kg) were given to rats, it was found that the higher the
STZ dose, the lower was the hepatic glycogen content and the smaller was
the glycemic response to neostigmine. Our results indicate that, in severe
diabetes, CNS stimulation with neostigmine fails to increase hepatic
glucose output, because glycogen stores are nearly exhausted and
gluconeogenesis is already maximal.
