Assay Method Information

Assay Name:  Assay for Dopamine Reuptake Inhibition
Description:  Uptake inhibition assay for the dopamine transporter was conducted in rat brain synaptosomes as described elsewhere with minor modifications (Rothman et al., Synapse 39, 32-41 (2001)). Freshly removed caudate was homogenized in 10% ice-cold sucrose with 12 strokes of a hand-held Potter-Elvehjem homogenizer followed by centrifugation at 1000g for 10 min. The supernatants were saved on ice and used immediately. Transporter activity was assessed using 5 nM [3H]dopamine. The assay buffer was Krebs-phosphate buffer containing 154.4 mM NaCl, 2.9 mM KCl, 1.1 mM CaCl2, 0.83 mM MgCl2, 5 mM glucose, 1 mg/mL ascorbic acid, and 50 μM pargyline. The selectivity of the uptake assay for DAT was optimized by including 100 nM citalopram and 100 nM desipramine as blockers of SERT and NET in the sucrose solution and assay buffer. Uptake inhibition assays were conducted at 25 C. and were initiated by adding 100 μl of tissue to 900 μL assay buffer containing test drug and [3H]dopamine. Test drugs were diluted in assay buffer containing 1 mg/mL bovine serum albumin. Nonspecific uptake was measured by incubating in the presence of 10 μM indatraline. The reactions were stopped after 15 minutes by rapid vacuum filtration with a cell harvester (BRANDEL) over GF/B filters (Whatman) presoaked in wash buffer maintained at 25 C. (10 mM Tris-HCl, pH 7.4/150 mM NaCl). Filters were rinsed with 6 mL wash buffer and retained tritium was quantified by a MicroBeta liquid scintillation counter (PerkinElmer) after overnight extraction in 0.6 mL of liquid scintillation cocktail (Cytoscint, ICN). The data from three experiments were pooled and fit to a dose-response curve equation (using Kaleidagraph), to yield an Emax and EC50 value.
Affinity data for this assay
 

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