The Effect Of Glucose On Reward Feeding Behavior And Dopamine Neurons

Glucose is an essential nutrient for organism to maintain normal physiological activities.The change of glucose concentration in the body can produce a variety of fine regulation on different sites and different neurons in the nervous system.Studies have shown that abnormal glucose levels are associated with anxiety symptoms and changes in motivational behavior.However,the specific role of glucose concentration and abnormal glucose uptake patterns in motivational behavior remains unclear.This study by intraperitoneal injection of strepotocozin to create ‘low glucose availability model’ and by long time high concentration of sucrose water intake to create ‘high glucose availability model’,Using the exploration of the reward behavior and decisionmaking behavior paradigm test animals in two different cases of motivation behavior change.By means of in vitro electrophysiological study on the level of neuron,looking for two kinds of model reward related changes of the neurons.After intraperitoneal injection of 200mg/kg streptozotocin to induce type I diabetes,model mice showed symptoms of weight loss,increased water consumption,increased urine,and increased fasting blood glucose levels and decreased glucose metabolism.We observed changes in the animals’ exploratory behavior based on food rewards at 4days after injection which there was a significant difference in water intake and body weight。The model mice were more induced by high-fat diet to increase the time spent exploring the central area of the open field test.In the running wheel test,which measured voluntary exercise motivation,the model mice showed a significant decrease in exercise motivation.In vitro electrophysiological tests of dopaminergic neurons in the ventral tegmental region showed a significant decrease in basal firing frequency and hyperpolarized activated cation channel(IH)amplitude in model mice.After 8 weeks of drinking a high-concentration(25%)sucrose solution in a two bottle-choice mode,sucrose-drinking animals showed reduced motivation to consume high-fat foods.At the same time,the decrease in exploration time to the central area of open field induced by high fat food was reduced.After eight weeks of drinking water with 25% sucrose,the animals’ glucose tolerance was found to be partially impaired.No significant changes in long-term sucrose drinking were found on anxiety behavior tests,effort-based reward behavior tests,and voluntary exercise motivation tests.In vitro electrophysiological tests of dopaminergic neurons in the ventral tegmental region on isolated brain slices showed a decrease in cell excitability in animals drinking chronic high concentrations of sucrose.In summary,this study found two types of abnormal glucose utilization in animals that induced changes in exploratory behavior in response to high-fat food.Increased motivation to eat high-fat foods was found in models of type 1 diabetes with chronic extracellular high glucose levels but no access to them.It was found that the high-fat food and the high-fat food-induced exploration behavior were decreased in sucrose-drinking model which had been drinking of 25% sucrose for a long time but could use glucose normally.In this study,we explored the changes of reward motivation for high-fat food in mice under abnormal glucose utilization and related neuronal studies,which provided a theoretical basis for clinical studies to seek for alleviating reward motivation disorder in patients with abnormal glucose utilization.