A cell line engineered to stably express a human NaV 1.7 comprising a NaV alpha 9 subunit, a NaV beta 1 subunit, and a NaV beta 2 subunit, wherein the cell line is produced by a method comprising the steps of: a) providing a plurality of cells that express mRNA(s) encoding the human NaV 1.7; b) dispersing the cells individually into individual culture vessels, thereby providing a plurality of separate cell cultures; c) culturing the cells under a set of desired culture conditions using an automated cell culture method characterized in that the conditions are substantially identical for each of the separate cell cultures, during which culturing the number of cells per separate cell culture is normalized, and wherein the separate cultures are passaged on the same schedule; d) assaying the separate cell cultures to measure expression of the human NaV 1.7 at least twice and to measure a Z' factor in the membrane potential assay; and e) identifying a separate cell culture that expresses the human NaV 1.7 at a consistent level in both assays and produces a Z' factor of at least 0.6 in the membrane potential assay, thereby obtaining said collection of cells; wherein the membrane potential assay comprises: i) plating cells from the cell line at 10,000 - 25,000 cells per well in a 384-well plate in growth media; ii) maintaining the cells in the 384-well plate in a 37°C cell culture incubator under 5% CO 2 for 22-24 hours; iii) removing the growth media from the 384-well plate; iv) incubating the cells in the 384-well plate with a blue florescence membrane potential dye diluted in a load buffer comprising 137 mM NaCl, 5 mM KCl,1.25 mM CaCl 2, 25 mM HEPES, 10 mM glucose for 1 hour at 37°C; v) adding to the incubated cells a) 25 μM of veratridine and 5-25 μg/ml of scorpion venom for positive control wells; or b) a control buffer for negative control wells; vi) loading the 384-well plate onto a high-throughput fluorescent plate reader; and vii) measuring cell fluorescence signals of the positive control wells and the negative control wells, wherein the Z' factor is calculated using the measured cell fluorescence signals from step vii) and using the equation: Z ′ factor = 1 − 3 σ positive control + 3 σ negative control / μ positive control − μ negative control, wherein σ positive control represents a standard deviation from the positive controls of the assay; σ negative control represents a standard deviation from the negative controls of the assay; μ positive control represents the mean value of the positive controls; and μ negative control represents the mean value of the negative controls. a) providing a plurality of cells that express mRNA(s) encoding the human NaV 1.7; b) dispersing the cells individually into individual culture vessels, thereby providing a plurality of separate cell cultures; c) culturing the cells under a set of desired culture conditions using an automated cell culture method characterized in that the conditions are substantially identical for each of the separate cell cultures, during which culturing the number of cells per separate cell culture is normalized, and wherein the separate cultures are passaged on the same schedule; d) assaying the separate cell cultures to measure expression of the human NaV 1.7 at least twice and to measure a Z' factor in the membrane potential assay; and e) identifying a separate cell culture that expresses the human NaV 1.7 at a consistent level in both assays and produces a Z' factor of at least 0.6 in the membrane potential assay, thereby obtaining said collection of cells; i) plating cells from the cell line at 10,000 - 25,000 cells per well in a 384-well plate in growth media; ii) maintaining the cells in the 384-well plate in a 37°C cell culture incubator under 5% CO 2 for 22-24 hours; iii) removing the growth media from the 384-well plate; iv) incubating the cells in the 384-well plate with a blue florescence membrane potential dye diluted in a load buffer comprising 137 mM NaCl, 5 mM KCl,1.25 mM CaCl 2, 25 mM HEPES, 10 mM glucose for 1 hour at 37°C; v) adding to the incubated cells a) 25 μM of veratridine and 5-25 μg/ml of scorpion venom for positive control wells; or b) a control buffer for negative control wells; vi) loading the 384-well plate onto a high-throughput fluorescent plate reader; and vii) measuring cell fluorescence signals of the positive control wells and the negative control wells,