Development of a model for excitability studies using Xenopus oocytes

ORCiD

Carlos A. Villalba-Galea: 0000-0002-6489-4651

Document Type

Poster

Conference Title/Conference Publication

Biophysical Journal

Organization

Biophysical Society 59th Annual Meeting

Location

Baltimore, MD

Conference Dates

February 7-11, 2015

Date of Presentation

2-7-2015

ISSN

0006-3495

Volume

108

Issue

2, Supplement 1

DOI

10.1016/j.bpj.2014.11.1534

First Page

281a

Abstract

Action potentials (AP) are basic functional units of electrical signaling in excitable cells. These electrical signals are involved in many biological processes, including muscle contraction, synaptic transmission and hormone release. In general, the plasma membrane is polarized, displaying a difference in electric potential (membrane potential) with a negative intracellular voltage with respect to the extracellular space. During an AP, the membrane potential is momentarily canceled (depolarized) or reverted (anti-polarized) by a inwardly-rectifying current typically mediated by sodium-selective voltage-gated channels (VGC); the membrane potential is returned back (repolarize) to its initial voltage (resting potential) by a outwardly-rectifying current mediated by potassium-selective VGC. The temporal and electrical characteristics of APs depend on which VGCs are present in the membrane. Understanding the role of VGCs in AP generation in their native cells constitutes a difficult task, commonly riddled with the use of pharmacological agents to isolate each specific conductance. Here, we have developed a model to study cellular excitability using Xenopus oocytes. Spontaneous and evoked APs were readily recorded from oocytes expressing Nav1.4, Drosophila Kv1.1 (Shaker), human Kv7.2 and Kv7.3. These APs were around 5-ms long. However, in the absence of Shaker, the AP lasted about 50 ms. These observations indicated that we were able to modify the temporal characteristic of APs by removing the fast-activating Shaker. To further validate this model, we used the Kv7.2-7.3 agonist diclofenac seeking to decrease excitability. The addition of diclofenac drove the resting potential to more negative voltages and raised the threshold for excitation, effectively decreasing excitability. These results constitute proof of concept showing that this type of models can be used as functional scaffolds for the evaluation of pharmacological agents and the assessment of the effect of mutations in VGCs on the generation of bioelectrical signals.

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