Electrophysiological and pharmacological properties of the human brain type IIA Na + channel expressed in a stable mammalian cell line

Abstract

The human brain voltage-gated Na+ channel type IIA alpha subunit was cloned and stably expressed in Chinese hamster ovary cells and its biophysical and pharmacological properties were studied using whole-cell voltage-clamp. Fast, transient inward currents of up to -8,000 pA were elicited by membrane depolarization of the recombinant cells. Channels activated at -50 mV and reached maximal activation at -10 mV to 0 mV. The reversal potential was 62 +/- 2 mV which is close to the Na+ equilibrium potential. The half-maximal activation and inactivation voltages were -24 +/- 2 mV and -63 +/- 1 mV, respectively. Currents were reversibly blocked by tetrodotoxin with a half-maximal inhibition of 13 nM. The effects of four commonly used anti-convulsant drugs were examined for the first time on the cloned human type IIA channel. Lamotrigine and phenytoin produced concentration- and voltage-dependent inhibition of the type IIA currents, whereas, sodium valproate and gabapentin (up to 1 mM) had no effect. These results indicate that recombinant human type IIA Na+ channels conduct tetrodotoxin-sensitive Na+ currents with similar properties to those observed in recombinant rat brain type IIA and native rat brain Na+ channels. This stable cell line should provide a useful tool for more detailed characterization of therapeutic modulators of human Na+ channels.

Low Somatic Sodium Conductance Enhances Action Potential Precision in Time-Coding Auditory Neurons

“…Experimental procedures were approved by the Institutional Animal Care and Use Committee at the University at Buffalo. Slices were prepared from P14-P25 CBA/CaJ mice (RRID:IMSR_JAX: 000654) of either sex as described previously (Ngodup et al, 2015;Yang and Xu-Friedman, 2015). Briefly, slices (150 m) were cut in an ice-cold solution containing the following (in mM): 76 NaCl, 75 sucrose, 25 NaHCO 3 , 25 glucose, 2.5 KCl, 1.25 NaH 2 PO 4 , 7 MgCl 2 , and 0.5 CaCl 2 .…”

“…The Markov feature of mafDC was used to apply g Na (Yang et al, 2015). The Na channel model was based on the Na currents recorded in Figure 2.…”

“…The most common ␣ subunits in the CNS are Na V 1.1, 1.2, 1.3, and 1.6 (Smith and Goldin, 1998;Yu and Catterall, 2003). In expression systems, Na V 1.6 appears to have the most hyperpolarized inactivation sensitivity, ranging from V 1/2 ϭ Ϫ48 to Ϫ69 mV in different studies (Isom et al, 1992;Xie et al, 2001;Burbidge et al, 2002;Chen et al, 2008;He and Soderlund, 2014). ␤ subunits could also contribute to inactivation voltage sensitivity, depending on the specific ␣ and ␤ subunit (Smith and Goldin, 1998;Meadows et al, 2002;Zhao et al, 2011;Calhoun and Isom, 2014).…”

“…They also help suppress APs driven by asynchronous neurotransmitter release (Yang and Xu-Friedman, 2010).…”

Ion Channels as Drug Targets in Central Nervous System Disorders

“…They are phenyl ring and amino group in position five of the triazine, which is moved from aromatic ring at the distance of three chemical bonds [46]. The binding affinity of LTG to rat brain Na V 1.2 expressed in Xenopus oocytes in inactivated state was reported to be 31.9 M [54] while compound's affinity to the closed state of the channel was very low (IC 50 641 M; inhibition of peak current at -90 mV in human Na V 1.2 -subunit expressed in Chinese hamster ovary (CHO) cells) [55]. Many compounds with LTG related structure were synthesized.…”