Hair cells with heterogeneous transfer characteristics encode mechanical stimuli in the lateral line of zebrafish

Abstract

Ribbon synapses of hair cells transmit mechanical information but the transfer characteristics relating deflection of the hair bundle to glutamate release have not been assessed directly. Here we have imaged glutamate to investigate how hair cells encode information in the lateral line of zebrafish. Half the hair cells signalled cupula motion in either direction from rest, achieving maximum sensitivity for deflections of ~40 nm in the preferred direction. The remainder rectified completely and were less sensitive, extending the operating range of the neuromast beyond 1μm. Adaptation was also heterogeneous, with some hair cells generating sustained synaptic outputs and others transient. A unique signal encoded a return to rest: a transient burst from hair cells unresponsive to the initial stimulus. A mixed population of hair cells with these various transfer characteristics will allow a neuromast to encode weak stimuli as well as the amplitude and duration of stronger deflections.