Insulin-mediated effects of glucose on dopamine metabolism.

Administration of various doses of glucose to rats produced a significant decrease of dopamine turnover in both striatum and olfactory tubercle. From the dose-response curve, a close connection between 3.4-dihydroxyphenylacetic acid (DOPAC) variation and insulin plasma level was demonstrated. However, glucose did not affect dopamine metabolism in starved or streptozotocin-treated rats. This indicates that the effect of glucose on the central dopaminergic system is mediated by pancreatic insulin, even in the presence of endogenous brain insulin. Therefore, insulin may influence synaptic transmission in the central nervous system.