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http://dx.doi.org/10.4196/kjpp.2015.19.4.383

Characteristics of K+ Outward Currents in the Cochlear Outer Hair Cells of Circling Mice within the First Postnatal Week  

Ahn, Ji Woong (Department of Physiology, College of Medicine, Dankook University)
Kang, Shin Wook (Department of Physiology, College of Medicine, Dankook University)
Ahn, Seung Cheol (Department of Physiology, College of Medicine, Dankook University)
Publication Information
The Korean Journal of Physiology and Pharmacology / v.19, no.4, 2015 , pp. 383-388 More about this Journal
Abstract
$K^+$ outward currents in the outer hair cells (OHCs) of circling mice (homozygous (cir/cir) mice), an animal model for human deafness (DFNB6 type), were investigated using a whole cell patch clamp technique. Littermate heterozygous (+/cir) mice of the same age (postnatal day (P) 0-P6) were used as controls. Similar slow rising $K^+$ currents were observed in both genotypes, but their biophysical and pharmacological properties were quite different. The values of Vhalf for activation were significantly different in the heterozygous (+/cir) and homozygous (cir/cir) mice ($-8.1{\pm}2.2mV$, heterozygous (+/cir) mice (n=7) and $-17.2{\pm}4.2mV$, homozygous (cir/cir) mice (n=5)). The inactivation curve was expressed by a single first order Boltzmann equation in the homozygous (cir/cir) mice, while it was expressed by a sum of two first order Boltzmann equations in the heterozygous (+/cir) mice. The $K^+$ current of homozygous (cir/cir) mice was more sensitive to TEA in the 1 to 10 mM range, while the 4-AP sensitivities were not different between the two genotypes. Removal of external $Ca^{2+}$ did not affect the $K^+$ currents in either genotype, indicating that the higher sensitivity of $K^+$ current to TEA in the homozygous (cir/cir) mice was not due to an early expression of $Ca^{2+}$ activated $K^+$ channels. Our results suggest that the $K^+$ outward current of developing homozygous (cir/cir) mice OHCs is different in both biophysical and pharmacological aspects than that of heterozygous (+/cir) mice.
Keywords
Circling mice; Deafness; DFNB6; $K^+$ current; Outer hair cell;
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