Preferential Transport and Metabolism of Glucose in Bergmann Glia over Purkinje Cells: a Multiphoton Study of Cerebellar Slices

Knowing how different cell types handle glucose should help to decipher how energy supply is adjusted to energy demand in the brain. Previously, the uptake of glucose by cultured brain cells was studied in real-time using fluorescent tracers and confocal microscopy. Here, we have adapted this technique to acute slices prepared from the rat cerebellum by means of multiphoton microscopy. The transport of the fluorescent glucose analogs 2NBDG and 6NBDG was several-fold faster in the molecular layer of the cerebellar cortex than in Purkinje cell somata and granule cells. After washout of free tracer, it became apparent that most phosphorylated tracer was located in Bergmann glia, which was confirmed by counterstaining with the glial marker sulforhodamine 101. The effective recovery of fluorescence after photobleaching showed that 2NBDG-P can diffuse horizontally across the molecular layer, presumably through gap junctions between Bergmann glial cells. Our main conclusion is that in acute cerebellar slices, the glucose transport capacity and glycolytic rate of Bergmann glia are several-fold higher than those of Purkinje cells. Given that the cerebellum is largely fueled by glucose and Purkinje neurons are estimated to spend more energy than Bergmann glial cells, these results suggest substantial shuttling of an energy-rich metabolite like lactate between glial cells and neurons.