# Role of Kir4.1 Channel in Auditory Function: Impact on Endocochlear Potential and Hearing Loss
## 4 Discussion
### Kir4.1 Channel  
#### 4.3.1 Kir4.1 Channel  
The KCNJ10 gene encodes the Kir4.1 channel, expressed in glial cells of the brain and kidney, but also in the inner ear, particularly in the lateral cochlear wall, spiral ganglion cells, and supporting cells in the organ of Corti [22; 23; 24] (Figure 2).  
This channel, also known as inactivable internally rectified potential 4.1, is an important component of the ion channels in the cochlea, crucial to maintaining ion homeostasis and for the generation and maintenance of the cochlear EP, critical for sound transduction in the inner ear [11; 14; 22; 23; 24; 25; 26; 27; 28]. The loss of endocochlear potential and degeneration of inner ear structures result in profound deafness and decreased acoustic responses in mice that lack KCNJ10 [14; 29]. In particular, intermediate cells express the Kir4.1 channel at their apical membrane [14]. Cells in stria vascularis are divided into three types: marginal, basal, and intermediate. The marginal cells form a layer that continuously extends to the endolymph, while the basal cell layer borders the spiral ligament that is filled with perilymph [11]. Between the two layers, intermediate cells and capillaries are scattered. In these cells, there are multiple ion transporters and channels that could be the reason for the creation of EP and an endolymphatic high [K+]. Between marginal cells and the basal cells along the stria vascularis in the lateral wall of the cochlea in the inner ear, there is an intrastrial space with a low [K+] and a high positive potential (more than the EP of 10-15 mV). Kir4.1 is expressed in the apical membranes of intermediate cells, where it maintains the equilibrium of potassium ion concentration and generates the transmembrane potential [14; 28; 30]. Kir4.1's role in potassium recycling is confirmed by its expression in root cells [31; 32].  
Furthermore, the Kir4.1 channel is found in supporting cells, primarily in glial cells that provide metabolic support, near outer hair cells and spiral ganglion neurons, contributing to the balance of extracellular potassium ions necessary for hair cell function and hearing transduction, in addition to potassium recirculation in the cochlea [28; 33]. In detail, Kir4.1 in glial cells plays a significant role in maintaining resting potential and regulating ionic homeostasis in the extracellular environment near neurons. Hair cells release neurotransmitters that stimulate cochlear ganglion neurons, which are bipolar sensory neurons. Signals are sent by these neurons to the cochlear nucleus, which, through the auditory neural pathway, reach the central auditory system. More than two satellite glial cells typically surround cochlear ganglion neurons, as in other types of sensory and autonomous ganglia. It has been found by electron microscope imaging that the satellite glial cells in the cochlear ganglion wrap the soma of the neurons in the ganglion with multiple layers of myelin sheaths, where Kir4.1 is present [34]. Regarding the subcellular localization of Kir4.1, satellite glial cells have been suggested to be able to absorb K+ ions that ganglion neurons release during excitation [14; 30].