Effects of hypothalamic stimulation on gluconeogenesis and glycolysis in rat liver

Hypothalamic effects on gluconeogenesis and glycosis in rat liver were studied byelectrical stimulations of the ventromedial hypothalamic nucleus (LH) without disturbing the animal's behavior. Stimulation of VMH caused a increase in the activity of phosphoenolpyruvate carboxykinase (PEPCK), a key gluconeogenic enzyme, and marked suppression of pyruvate kinase (PK), a key glycolytic enzyme, of the liver. Stimulationof LH, on the other hand, resulted in a decrease in PEPCK activity but did not alterPK activity. The maximal responses of these enzymes to hypothalamic stimulations were obtained after intermittent stimulations for 4 h. Differential estimations of thetwo isozymes of liver PK (types L and M) were made using antibody against typeM PK. The level of type M enzyme was not altered significantly on stimulation of either VMH or LH. The content of type L enzyme greatly decreased on stimulation of VMH but was not affected by stimulation of LH. The reciprical influences of VMH and LH on hepatic carbohydrate metabolism and their relation to neural-hormonal responses are discussed.