Transmission between the type I hair cell and its calyx ending

The long, uninterrupted apposition between the type I hair cell and the calyx ending has implications for the intercellular communication between these structures. Conventional synaptic transmission will be compromised unless the impedance of the ending is made relatively high. The apposition also creates the possibility of ephaptic transmission between the hair cell and the ending. Ephaptic transmission from the hair cell to the outer face of the calyx ending is too weak to make more than a minor contribution to sensory coding. Basolateral currents associated with hair-cell transduction can result in a substantial accumulation of K+ ions in the intercellular space. The accumulation can alter conventional transmission by depolarizing the hair cell and can alter afferent firing by depolarizing the ending. Reasons were presented suggesting that K+ accumulation may play an essential role in transduction involving type I hair cells, including the linearization of input-output relations and an increase in the maximal rate of discharge.