Assay Method Information
Assay Name:  Competitive Radioligand Binding Assay
Description:  Radioligand binding assays for Sigma-1 receptors and Sigma-2 receptors were carried out by a commercial contract research organization. For Sigma-1 binding, various concentrations of test compounds from 100 μM to 1 nM were used to displace 8 nM [3H](+)pentazocine from endogenous receptors on Jurkat cell membranes (Ganapathy M E et al. 1991, J Pharmacol. Exp. Ther. 289:251-260). 10 μM Haloperidol was used to define non-specific binding. For Sigma-2 receptors various concentrations of test compounds from 100 μM to 1 nM were used to displace 5 nM [3H] 1,3-Di-(2-tolyl)guanidine from endogenous receptors on membranes from rat cerebral cortex in the presence of 300 nM (+)pentazocine to mask Sigma-1 receptors. (Bowen W D, et al. 1993, Mol. Neuropharmcol 3:117-126). 10 μM Haloperidol was used to define non-specific binding. Reactions were terminated by rapid filtration through Whatman GF/C filters using a Brandel 12R cell harvester followed by two washes with ice-cold buffer. Radioactivity on the dried filter discs was measured using a liquid scintillation analyzer (Tri-Carb 2900TR; PerkinElmer Life and Analytical Sciences). The displacement curves were plotted and the Ki values of the test ligands for the receptor subtypes were determined using GraphPad Prism (GraphPad Software Inc., San Diego, Calif.). The percentage specific binding was determined by dividing the difference between total bound (disintegrations per minute) and nonspecific bound (disintegrations per minute) by the total bound (disintegrations per minute).Affinities for Sigma-1 and Sigma-2 receptors are typically obtained from published studies using cerebral tissue homogenates with [3H](+)pentazocine to measure displacement from Sigma-1 receptors and [3H] 1,3-Di-(2-tolyl)guanidine in the presence of 300 nM (+)pentazocine to measure displacement from Sigma-2 receptors.
Affinity data for this assay
 
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