Cocaine inhibits tritium-labeled dopamine ([3H]DA) uptake in rat (IC50≈400 nM) and sheep (IC50≈1 μM) striatum. GBR 12909, a selective DA uptake inhibitor, potently inhibits [3H]DA uptake in rat (IC50<10 nM), but is less effective (only 60% of the uptake is inhibited at a concentration of 10 μM) and less potent (IC50≈300 nM) in sheep. [3H]DA release from slices of rat or sheep striatum is stimulated by potassium (15-50 mM). In the presence of nomifensine (10 μM), cocaine (10 μM) had no effect on potassium-stimulated [3H]DA release in either species. [3H]DA release in increased by N-methyl-D-aspartate (NMDA) (10-1000 μM) in rat striatum but NMDA did not stimulate [3H]DA release in sheep striatum. These findings suggest that NMDA receptors either are absent from or do not regulate release of preloaded [3H]DA in sheep striatum.
ASJC Scopus subject areas
- Biochemistry, Genetics and Molecular Biology(all)
- Pharmacology, Toxicology and Pharmaceutics(all)