The Role of the Central Parasympathetic Nervous System in Modulating Glucose Metabolism in Streptozotocin-induced Diabetic Rats

Insulin controls the levels of blood sugar by inhibiting glucose release from liver and by stimulating glucose utilization in muscle and adipose tissues. In addition to its peripheral effects, insulin influences circulating glucose levels by modulating glucose production and its metabolism through central nervous system. But it is presently not well known whether the central effect of insulin on plasma glucose is mediated by directly or indirectly through CNS actions. The autonomic nervous system exerts a dual control over insulin secretion. The parasympathetic nervous system can augment insulin secretion and the sympathetic nervous system can produce a net impairment of insulin release.

In the present study, we measured the changes of blood glucose and pyruvic acid level to examine the effetcs of intracisternally injected insulin. Carbachol and scopolamine in streptozotocin(STZ)-induced diabetic rats.

results are as follows:

1) streptozotocin produced significant increase in blood glucose and pyruvic acid concentrations.

2) Intracisternally injected insulin markedly reduced blood glucose and pyruvic acid concentrations in STZ-induced diabetic rats.

3) Intracisternally injected cholinominetics, carbachol, reduced blood glucose and pyruvic acid concentrations in STZ-induced diabetic rats.

4) Intracisternally injected anticholinergics, scopolamine, increased the concentration of the blood glucose and inhibited the concentration of the blood pyruvic acid in STZ-induced diabetic rats.

Therefore, it is suggested that central parasympathetic nervous system plays an partial role in modulating peripheral blood glucose metabolism and insulin produse hypoglycemic action via central parasympathetic nervous system.