EFFECT OF HYPOXIA AND GLUCOSE DEPRIVATION ON ATP LEVEL, ADENYLATE ENERGY-CHARGE AND [CA2-DEPENDENT AND INDEPENDENT RELEASE OF [H-3] DOPAMINE IN RAT STRIATAL SLICES(](O))

Release of [H-3]dopamine ([H-3]DA) from rat striatal slices kept under hypoxic or/and glucose-free conditions was measured using a microvolu me perfusion method. The corresponding changes in nucleotide content w ere determined by reverse-phase high-performance liquid chromatography (RPHPLC). The resting release [H-3]DA was not affected by hypoxia. bu t under glucose-free conditions massive [Ca2+](o)-independent release of [H-3]DA was observed. Hypoxia reduced the energy charge (E.C.) and the total purine content from 19.36+/-4.15 to 6.98+/-1.83 nmol/mg prot ein. Glucose deprivation by itself, or in combination with hypoxia, ma rkedly reduced the levels of adenosine 5'-triphosphate (ATP), adenosin e diphosphate (ADP) and adenosine monophosphate (AMP). The E.C. under glucose-free conditions wa significantly reduced from 0.73+/-0.04 to 0 .44+/-0.20. When the tissue was exposed to hypoxic and glucose-free co nditions for 18 min the level of ATP was reduced to 3.15+/-0.11 nmol/m g protein. However. when the exposure time was 30 min the ATP level wa s further reduced to 1.11+/-0.37 nmol/mg protein. The resting release was enhanced in a [Ca2+](o)-independent manner, but there was no relea se in response to stimulation, and tetrodotoxin did not affect the enh anced resting release, indicating that the release was nor associated with axonal activity. Similarly, 50 mu M ouabain, inhibitor of Na+/K+- activated ATPase, enhanced the release of [H-3]DA at rest in a [Ca2+]( o)-independent manner. It seems very likely that the reduced ATP level under glucose-free conditions leads to an inhibition of the activity of Na+/K+ ATPase that results in reversal of the uptake processes and in [Ca2+](o)-independent [H-3]DA release from the axon terminals. Copy right (C) 1996 Elsevier Science Ltd.