Hair-Cell Transduction Mechanisms

Abstract

The simple structure of the lateral-line organ of the toad Xenopus laevis makes it ideal for the study of sensory transduction in hair-cell systems. When mounted in a specially designed chamber, the end organ is readily accessible for precisely controlled mechanical, electrical, or chemical stimulation and the afferent fibers are available for recording neural activity. In addition, the chamber prevents movement of the preparation during stimulation consisting of either fluid flow past the cupula or fluid pressure variation. There was no response to constant or alternating pressure and only a transient response to a constant laminar flow of water. Sinusoidal movements of water past the cupula resulted in an increase in the mean firing rate and in a sinusoidal modulation of the spontaneous activity over a stimulus frequency range of 0.25 to 40 Hz. These results not only imply that a displacement of the cupula (and the hair-cell cilia) is the necessary stimulus for neural excitation but also suggest that the transduction process is dependent upon a continuously varying rather than constant displacement of the cilia.