Selective alteration of neurotransmitter release by low oxygen in vitro.

The potassium-stimulated release of acetylcholine, norepinephrine, serotonin, glutamate, and 4-aminobutyrate from superfused rat cortical slices was studied during hypoxia. A reduction in oxygen tensions from 603 +/- 6 to 22 +/- 2 mm Hg selectively altered the calcium-dependent efflux of these neurotransmitters, but did not change their calcium-independent release. The calcium-dependent release of [14C]acetylcholine decreased (39%), while that of glutamate increased (66%) and 4-aminobutyrate, [3H]norepinephrine, and [3H]serotonin were unaffected. Thus, low oxygen reveals variations in the calcium-dependent release mechanisms of several neurotransmitters. These differences may have important implications for pharmacological intervention of neurotransmitter release.