Effect of Experimental Diabetes on the Catecholamine Metabolism in Rat Brain

The levels of epinephrine, norepinephrine, and dopamine and the activities of tyrosine hydroxylase and monoamine oxidase were estimated in four regions of rat brain during alloxan-induced hyperglycemia and insulin-induced hypoglycemia. Catecholamine levels were estimated by HPLC, and the insulin levels were quantified by radioimmunoassay. The results demonstrated significant increases in the activities of the metabolizing enzymes and levels of catecholamines during experimental conditions. The levels of catecholamines were highest in the cerebral hemispheres, the region associated with high activities of the metabolizing enzymes. Insulin-induced hypoglycemia caused a decrease in the activities of the metabolizing enzymes followed by their recovery within 2 h.