The effect of norepinephrine and depolarizing agents on 14C-glucose metabolism in rat brain

Hexose monophosphate (HMP) shunt activity was examined by an isotopic method based on measurements of the conversion of 1-(14)C-glucose and 6-(14)C-glucose to 14CO2, yielding 1-(14)C/6-(14)C ratio in slices from different parts of rat brain in the range of 2.5 to 5.0 after 15 min incubation of the slices at 37 degrees C. The influence of noradrenaline (NE), high K+ concentration, ouabaine and glutamate was evaluated. NE (1 mM) caused a pronounced stimulation of HMP activity in cortical, hypothalamic and striatal slices. This effect was observed only in the presence of ascorbate in the incubation medium. The experiments with dibutyrylc-AMP, theophylline and alpha and beta adrenoreceptor blocking agents suggest that the cyclic AMP-dependent mechanism is not involved in the NE stimulation of HMP shunt. Moreover, neither basal glucose metabolism (glycolysis and 14C-glucose incorporation into 14CO2, lipid, protein and nucleic acid fractions) nor SH group level were affected by the neurotransmitter.