An M-Like Potassium Current in the Guinea Pig Cochlea

Abstract

Potassium M currents play a role in stabilizing the resting membrane potential. These currents have previously been identified in several cell types, including sensory receptors. Given that maintaining membrane excitability is important for mechano-electrical transduction in the inner ear, the presence of M currents was investigated in outer hair cells isolated from the guinea pig hearing organ. Using a pulse protocol designed to emphasize M currents with the whole-cell patch-clamp technique, voltage- and time-dependent, non-inactivating, low-threshold currents (the hallmarks of M currents) were recorded. These currents were significantly reduced by cadmium chloride. Results from RT-PCR analysis indicated that genes encoding M channel subunits KCNQ2 and KCNQ3 are expressed in the guinea pig cochlea. Our data suggest that guinea pig outer hair cells express an M-like potassium current that, following sound stimulation, may play an important role in returning the membrane potential to resting level and thus regulating outer hair cell synaptic mechanisms.

Electrophysiological and Molecular Analysis of Kv7/KCNQ Potassium Channels in the Inferior Colliculus of Adult Guinea Pig

“…However, the expression of different members of the Kv7 channels family has been previously reported using nonquantitative RT-PCR techniques in the peripheral auditory system. KCNQ1-3 mRNAs were found in the mouse and guinea pig cochlea (Kubisch et al 1999;Liang et al 2005;Kharkovets et al 2006;Liang et al 2006); KCNQ4 in the mouse, rat, and guinea pig cochlea (Kubisch et al 1999;Kharkovets et al 2000;Liang et al 2005;Kharkovets et al 2006;Liang et al 2006); and KCNQ5 in the guinea pig cochlea (Liang et al 2006). Recently, the presence of KCNQ2-4 transcripts in the cochlear complex of guinea pig and rat has also been reported (Liang et al 2006).…”

“…Expression of the five Kv7 channels in the peripheral auditory system (i.e., cochlea) has been previously reported in different mammalian species using reverse transcriptase polymerase chain reaction (RT-PCR; Kubisch et al 1999;Kharkovets et al 2000;Liang et al 2005;Kharkovets et al 2006;Liang et al 2006). Despite the clear implication of Kv7 channels in the auditory processing, there is relatively little information about their expression and function in auditory brainstem structures.…”

Molecular analyses of KCNQ1–5 potassium channel mRNAs in rat and guinea pig inner ears: expression, cloning, and alternative splicing

“…Methods for gene expression analysis were as previously described [4], with minor modification, i.e. smaller reaction volumes, optimization of annealing temperatures.…”

“…We have recently described the presence of a novel K ' current, with activation range ((/70 to (/10 mV) and reversal potential ( (/75 mV) characteristic of M currents, in the cochlea [4]. These M-like currents were recorded from outer hair cells (OHCs) isolated from the guinea pig cochlea using whole-cell patch-clamp technique at a holding potential of (/20 mV.…”

An in vitro model for testing drugs to treat tinnitus

“…Linopirdine is a potent K + channel blocker of the KCNQ4 sub-type and shows its greatest effect on the M-channel (Liang et al, 2005). The M-channel has been implicated also in the neurogenesis of tinnitus (Holt et al, 2007).…”