REGULATION OF ENERGY-METABOLISM BY NEUROTRANSMITTERS IN ASTROCYTES INPRIMARY CULTURE AND IN AN IMMORTALIZED CELL-LINE

Evidence suggests that astrocytes might play an important role in cere bral energy metabolism. A recently developed cell line, called DI TNC1 , displays several characteristic features of astrocytes. Thus, we hav e investigated in these cells a number of parameters related to energy metabolism. First, glycogen, the major energy reserve in the brain, i s present in these cells and its levels are influenced by the glucose content of the growth medium and the presence of serum. Second, severa l neurotransmitters including noradrenaline and vasoactive intestinal peptide (VIP) induce a glycogenolytic response. Their effect on glycog en is paralleled by a similar effect on the formation of cyclic AMP, w hich is presumably the second messenger involved. Third, noradrenaline stimulates glucose utilization (as reflected by 2-deoxyglucose uptake ) in DI TNC1 cells, an effect which is mimicked by the second messenge r arachidonate. Interestingly, two actions of neurotransmitters, which are well characterized in primary astrocytes, are absent in DI TNC1 c ells. These are the noradrenaline-and VIP-induced resynthesis of glyco gen and the glutamate-stimulated glycolysis. In summary, the observati ons reported here lend further support to the concept that astrocytes are important for the control of brain energy metabolism. In addition, DI TNC1 cells might represent an interesting preparation to help deci pher some of the astrocytic functions related to energy metabolism. (C ) 1997 Wiley-Liss.