K+ Accumulation and Clearance in the Calyx Synaptic Cleft of Type I Mouse Vestibular Hair Cells

Nonquantal Transmission at the Vestibular Hair Cell-Calyx Synapse: KLV Currents Modulate Fast Electrical and Slow K+ Potentials in the Synaptic Cleft

“…While the VHCC model results agree with experiments that show that changes in [𝐾 + ] 𝑆𝐶 affect both hair cell and calyx signals (Lim et al 2011;Contini et al 2012Contini et al , 2017Spaiardi et al 2020) the model shows a pivotal role for the synaptic cleft potential, 𝜙 𝑆𝐶 . The independent contributions of 𝜙 𝑆𝐶 and [𝐾 + ] 𝑆𝐶 to NQT are analyzed later.…”

“…The predictions of the VHCC model agree with experimental observations (Lim et al 2011;Contini et al 2012Contini et al , 2017Contini et al , 2020Spaiardi et al 2020) that support the hypothesis that K + currents through the basolateral membrane of the type I hair cell modulate [𝐾 + ] 𝑆𝐶 by changing 𝐸 𝐾 (Chen 1995;Goldberg 1996). The model further shows modulation of 𝜙 𝑆𝐶 that occurs on a faster time scale and alters both pre- Isolation of the contributions of 𝝓 𝑺𝑪 and [𝑲 + ] 𝑺𝑪 during step bundle displacements.…”

“…3D, Right). Analysis of the magnitude and time course of the currents shows that gK,L in the hair cell and KV7 channels in the calyx inner face membrane are primarily responsible for modulating [𝐾 + ] 𝑆𝐶 , as suggested previously (Spaiardi et al 2020).…”

“…In these formulations, hair cell transduction stimulates K + to flow from the hair cell into the cleft, depolarizing both hair cell and calyx primarily by K + accumulation, with negligible changes in the cleft electrical potential. Supporting this model are experimental results that emphasize the role of K + accumulation (Lim et al 2011;Contini et al 2012Contini et al , 2017Contini et al , 2020Spaiardi et al 2020). Alternative suggestions include accumulation in the cleft of glutamate released from synaptic vesicles (Dalet et al 2012;Sadeghi et al 2014) or protons (Highstein et al 2014).…”

“…Activation Kinetics in the model: (Spaiardi et al 2017(Spaiardi et al , 2020. 𝜏 𝐾,𝐿 is based on measurements of the slow time constant: (Wong et al 2004;Songer and Eatock 2013;Spaiardi et al 2017).…”