Radioligand Binding Assay: Radioligand Binding Studies: Saturation experiments. A representative compound of formula (I) was tritiated. Three tritiums were incorporated in place of methyl hydrogens to generate [3H]compound. Binding of this radioligand was preformed in 5 mL borosilicate glass test tubes at room temperature. Binding was initiated by adding membranes to increasing concentrations of [3H]compound in 100 mM NaCl, 20 mM Tris HCl, pH 7.4 buffer containing 0.01% w/v bovine serum albumin (BSA) for 18 h. Non-specific binding was determined in the presence of 1 uM unlabelled compound. After 18 h, the reactants were filtered through GF/C glass fiber filters presoaked in 0.5% w/v polyethylene imine. Filters were washed with 15 mL ice cold 100 mM NaCl, 20 mM Tris HCl, pH7.4 buffer containing 0.25% BSA to separate bound from free ligand. [3H]compound bound to filters was quantified by liquid scintillation counting.Competitive binding experiments.
Electrophysiological Assay: Patch voltage clamp electrophysiology allows for the direct measurement and quantification of block of voltage-gated sodium channels (NaV's), and allows the determination of the time- and voltage-dependence of block which has been interpreted as differential binding to the resting, open, and inactivated states of the sodium channel (Hille, B., Journal of General Physiology (1977), 69: 497-515).The following patch voltage clamp electrophysiology studies were performed on representative compounds of the invention using human embryonic kidney cells (HEK), permanently transfected with an expression vector containing the full-length cDNA coding for the desired human sodium channel alpha -subunit, grown in culture media containing 10% FBS, 1% PSG, and 0.5 mg/mL G418 at 37 C. with 5% CO2. HEK cells used for the electrophysiology (EP) recordings had a passage number of less than 40 for all studies and were used within three days from the time of plating.
Displacement of [3H]GX-545 from human Nav1.7 alpha subunit expressed in HEK293 cells co-expressing beta1 subunit by liquid scintillation counting analysis
Inhibition of human Nav1.7 alpha subunit expressed in HEK293 cells co-expressing beta1 subunit at -60 mV holding potential by whole-cell patch voltage clamp electrophysiology recording
Inhibition of human Nav1.5 alpha subunit expressed in HEK293 cells co-expressing beta1 subunit at -60 mV holding potential by PatchXpress automated voltage clamp electrophysiology technique
Inhibition of human Nav1.2 alpha subunit expressed in HEK293 cells co-expressing beta1 subunit at -35 mV holding potential by PatchXpress automated voltage clamp electrophysiology technique
Inhibition of human Nav1.1 alpha subunit expressed in HEK293 cells co-expressing beta1 subunit at -40 mV holding potential by PatchXpress automated voltage clamp electrophysiology technique
Inhibition of human Nav1.6 alpha subunit expressed in HEK293 cells co-expressing beta1 subunit at -35 mV holding potential by PatchXpress automated voltage clamp electrophysiology technique