Homozygous deletion of the gene of the neuronal glucose transporter GLUT3 (Slc2a3) in mice results in embryonic lethality, whereas heterozygotes (Slc2a3^+/-) are viable. Here we describe the characterization of heterozygous mice with regard to neuronal function, glucose homeostasis and, since GLUT3 might be a component of the neuronal glucose sensing mechanism, food intake and energy balance. Levels of GLUT3 mRNA and protein in brain were reduced by 50% in Slc2a3^+/- mice. Electrographic features examined by electroencephalographic recordings give evidence for slightly, but significantly enhanced cerebrocortical activity in Slc2a3^+/- mice. In addition, Slc2a3^+/- mice were slightly more sensitive to an acoustic startle stimulus (elevated startle amplitude and reduced prepulse inhibition). However, systemic behavioral testing revealed no other functional abnormalities e.g. in coordination, reflexes, motor abilities, anxiety, learning and memory. Furthermore, no differences in body weight, blood glucose and insulin levels were detected between wild-type and Slc2a3^+/- littermates. Food intake as monitored randomly or after intracerebroventricular administration of 2-deoxyglucose or D-glucose, or food choice for carbohydrates/fat was not affected in Slc2a3^+/- mice. Taken together, our data indicate that, in contrast to Slc2a1, a single allele of Slc2a3 is sufficient for maintenance of neuronal energy supply, motor abilities, learning and memory, and feeding behavior.