Voltage dependence of adaptation and active bundle movement in bullfrog saccular hair cells.

AUTOR(ES)

Assad, J A

RESUMO

Hair cells of the bullfrog sacculus adapt to maintained displacement stimuli in a manner that suggests an active regulation of the tension stimulus reaching transduction channels. We have examined adaptation in dissociated hair cells by whole-cell patch-clamp recording and video microscopy. Adaptation was present in these cells, and it depended on extracellular calcium. The adaptation rate--as well as the position of the resting current-displacement curve--also depended on membrane potential, suggesting that calcium passes into the cytoplasm to reach its site of action. After abrupt hyperpolarization, the adaptation rate increased within milliseconds, suggesting that the calcium site is within a few micrometers of the ion channels through which calcium enters. The voltage dependence of the resting current-displacement curve, together with the "gating springs" hypothesis for transduction, predicts movement of the bundle away from the kinocilium when the cell is depolarized. This was observed.

Documentos Relacionados

• Mechanical relaxation of the hair bundle mediates adaptation in mechanoelectrical transduction by the bullfrog's saccular hair cell.
• Kinetic analysis of voltage- and ion-dependent conductances in saccular hair cells of the bull-frog, Rana catesbeiana.
• Hair-bundle movements elicited by transepithelial electrical stimulation of hair cells in the sacculus of the bullfrog
• A model for electrical resonance and frequency tuning in saccular hair cells of the bull-frog, Rana catesbeiana.
• Activation and adaptation of transducer currents in turtle hair cells.