We previously demonstrated the presence of the glucose transporter GLUT2 in specific brain areas which are mainly involved in the control of fuel metabolism and feeding behavior, i.e., nuclei of the hypothalamus and of the anterior brainstem. We hypothesized that GLUT2 acts as a 'glucose sensor' in these areas, as already described in pancreatic beta cells. In order to test this hypothesis, we injected antisense unmodified oligodeoxynucleotide (ODN) to GLUT2 into the arcuate nucleus. Antisense ODN efficiency on GLUT2 protein level was assessed on pancreatic islets in culture and they were shown to induce a 66% decrease in GLUT2 protein. Bilateral injections of GLUT2 antisense ODNs were performed twice daily over a two-day period in rats. Antisense ODNs induced a significant decline in body weight gain although total daily food intake was unchanged when compared both to control groups and to the period before treatment. Twenty hours after the last injection, anaesthetized rats received, via a catheter inserted into the carotid artery and directed towards the brain, a minute glucose load that by itself does not modify systemic blood glucose level but which induces increased insulinemia. This insulin response was completely abolished only in antisense-treated rats. These findings provide the first evidence for a physiological role of GLUT2 in the brain and support the hypothesis that this transporter is involved in a 'glucose sensing'