| Assay Method Information | |
| | Automated Electrophysiology (Barra) |
| Description: | Ion Works Barracuda population patch clamp (PPC). PPC measurements were performed using an IonWorks Barracuda instrument (Molecular Devices Corporation, Union City, Calif.) using either PatchPlate PPC substrates (Molecular Devices Corporation) with 64 apertures per well. The ability to average currents from 64 recordings from each well greatly improves data consistency and recording success rates in the measurement of NaV1.7 mediated ionic currents. Calculated leak current was digitally subtracted from the total cell NaV1.7 current for each sample point acquired.NaV1.7 currents were elicited by a voltage clamp protocol designed to bias the NaV1.7 channels to their inactivated state as follows. From holding potential of −60 mV cells were briefly hyperpolarized to −100 mV for 1.25 sec, then stepped to −20 mV for 20 sec to inactivate the channels. This was followed by a relatively brief hyperpolarization to −100 mv for 300 ms, then a 20 msec test pulse to −20 mV to elicit the NaV1.7 current used to measure the pharmacology of all test compounds. Compounds were incubated for 600 sec between the pre- and post-compound reads. The external recording solution used was (in mM) 137 NaCl, 4 KCl, 1 MgCl2, 1.8 CaCl2, 10 Hepes, 10 glucose, pH to 7.4 with NaOH, and the internal solution used was (in mM) 100 K-gluconate, 40 KCl, 3.2 zMgCl2, 5 EGTA, 10 HEPES pH to 7.2 with KOH. The same solutions were used to record NaV1.5 currents, with the following voltage clamp protocol. NaV1.5 currents were elicited by a voltage clamp protocol designed to bias the NaV1.5 channels to their inactivated state as follows. From holding potential of −40 mV cells were briefly hyperpolarized to −100 mV for 300 ms, then stepped to −10 mV for 20 sec to inactivate the channels. This was followed by a relatively brief hyperpolarization to −100 mv for 30 ms, then a 20 msec test pulse to −10 mV to elicit the NaV1.5 current used to measure the pharmacology of all test compounds. HEK 293 cells expressing NaV1.7 and NaV1.5 channels, were used (Essen Biosciences, Ann Arbor, Mich.). Cells were cultured in T-175 flasks and passaged every 2 to 3 days at 1:3 to 1:6 seeding density dilutions. Cells were grown to 70% to 90% confluence in a flask and removed from the incubator (37° C., 5% CO2) 1 to 3 days after plating. Growth medium was aspirated from the culture flasks. Cells were gently rinsed with 10 ml of PBS (Catalog number: 14190144, Gibco) to remove residual media. Next a total of 2 mL TrypLE (Gibco) solution was added, and the flasks containing cells were sat for 3 min at RT, after which, the cells became visibly rounded and were easily dislodged from the bottom of the flask with a few brief taps on a solid surface. A total of 8 mL of media was added to the flask to inactivate the TrypLE, and the mixture was centrifuged at 910 rpm for 4 min. The cell supernatant was decanted, and the cell pellets were resuspended in 5-6 mL of external solution followed by gentle triturations using a 10 ml pipette, and transferred to a 15 ml conical tube and immediately brought to the IW Barracuda instrument. The cell suspension had a final concentration of 2 to 3 million cells per ml; this corresponds to 10,000 cells added per well.Peak membrane currents were analyzed with IW Barracuda software and exported to Excel for further analysis. Concentration response curve fitting was performed with BMS in-house software. IC50 values were obtained by fits of the Hill equation to the average percent inhibition data plotted versus compound concentration. Concentration-response curves for all test compounds were fitted to a 4-parameter equation: % of control=100 (1+([drug]/IC50)p)−1, where IC50 is the concentration of drug required to inhibit current by 50% and p is the Hill slope. |
| Affinity data for this assay | |
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