Nitric oxide induces calcium‐dependent release of [3H]dopamine release from striatal slices

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Abstract
Hydroxylamine (0.01–30 mM), a nitric oxide (NO) generator, produced a concentration-dependent release of [3H]dopamine ([3H]DA) from rat striatal slices. Hemoglobin (10 μM), a NO scavenger, reduced basal [3H]DA release and blocked hydroxylamine (100 μM)-stimulated [3H]DA efflux. Tetrodotoxin (0.5 μM) had no significant effect. Sodium cyanide was used as a model compound to test the possibility that NO acted through blockade of mitochondrial electron transport. Calcium-free experimental buffer (1 mM EGTA) reduced basal release and the hydroxylamine response, while sodium cyanide-induced release did not change under these experimental conditions. Cadmium (200 μM), a non-selective inhibitor of voltage-dependent calcium channels, reduced the hydroxylamine response by 69%. Methylene blue (10 μM), an inhibitor of guanylate cyclase, produced a 3-fold increase in the basal release but had no significant effect on the hydroxylamine response. These data suggest that NO induces calcium-dependent [3H]DA release from the striatum via a mechanism which is independent of blockade of electron transport or activation of guanylate cyclase.