DIETARY CARBOHYDRATES - EFFECTS ON SELF-SELECTION, PLASMA-GLUCOSE ANDINSULIN, AND BRAIN INDOLEAMINERGIC SYSTEMS IN RAT

The aim of the study was to investigate the effect of different dietar y carbohydrates such as corn starch, sucrose, fructose and glucose on carbohydrate and protein self-selection and on arterial and venous con centrations of glucose and insulin, and brain indoleamines in rats. Fr uctose and sucrose feeding induced the lowest food intakes which were due respectively to a lower carbohydrate and protein selection. The pr esent data showed that feeding with dietary glucose as the main carboh ydrate source gave the highest glycemic response, the lowest one being found with fructose and corn starch, and an intermediate one with suc rose feeding. The insulin response to the dietary carbohydrates follow ed a somewhat different pattern with the highest insulin secretion obs erved after fructose feeding whereas highly variable and inconsistent results were obtained following corn starch, sucrose and glucose feedi ng. Feeding chemically different sugars was also characterized by decr eased serotonin synthesis in the raphe nuclei, brainstem and thalamus, and increased 5-HT synthesis in the hypothalamus of rats fed fructose when compared to glucose fed animals. The present results highlight t he importance of considering the nature of dietary carbohydrates in th e regulation of feeding.