| Assay Method Information | |
| | [3H]Dihydrotetrabenazine ([3H]DTBZ) Binding Assay |
| Description: | Synaptic vesicles were prepared from rat brain using a modification of a previously described procedure (Teng et al., 1998). Briefly, fresh whole brain (excluding cerebellum) was homogenized using a Teflon pestle (clearance 0.003 inches) with 7 vertical strokes at 800 rpm in 20 vol of ice-cold 0.32 M sucrose and centrifuged at 1000 g for 12 min at 4 C. The resulting supernatant (S1) was then centrifuged at 22,000 g for 10 min at 4 C. The synaptosomal pellets (P2) were homogenized in 18 mL of ice-cold Milli-Q water and exposed for 5 min for lysing synaptosomes. Osmolarity was restored by addition of 2 mL of 25 mM HEPES with 100 mM dipotassium tartrate (pH 7.5). Samples were centrifuged at 20,000 g for 20 min at 4 C. to remove lysed synaptosomal membranes. MgSO4 (1 mM) was added to the supernatant (S3), and was centrifuged at 100,000 g for 45 min at 4 C. The final vesicular pellets (P4) were resuspended in ice-cold assay buffer (see below) providing 15 ug protein/100 uL, determined by the method of Bradford (1976) using bovine serum albumin as a the standard. Aliquot parts (100 uL) of suspension of vesicle membrane protein were incubated in assay buffer (25 mM HEPES, 100 mM dipotassium tartrate, 5 mM MgSO4, 0.1 mM EDTA and 0.05 mM EGTA, pH 7.5, at 25 C.) in the presence of 3 nM [3H]DTBZ and at least 7 concentrations (1 nM-1 mM) of compound for 1 hr at room temperature. Nonspecific binding was determined in the presence of 20 uM tetrabenazine, a standard compound. Assays were performed in duplicate using a 96-well plate format. Reactions were terminated by filtration of samples on a Unifilter-96 GF/B filter plates (presoaked in 0.5% polyethylenimine), using a FilterMate harvester (Packard BioScience Co., Meriden, Conn.). After washing 5 times with 350 uL of the ice-cold wash buffer (25 mM HEPES, 100 mM dipotassium tartrate, 5 mM MgSO4 and 10 mM NaCl, pH 7.5), filter plates were dried, sealed and each well filled with 40 uL Packard's MicroScint 20 cocktail. Bound [3H]DTBZ was measured using a Packard TopCount NXT scintillation counter with a Packard Windows NT based operating system. |
| Affinity data for this assay | |
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