The Passive Cable Properties of Hair Cell Stereocilia and Their Contribution to Somatic Capacitance Measurements

• Published in: Biophysical journal Vol. 96; no. 1; pp. 1 - 8
• Main Authors: Breneman, Kathryn D., Highstein, Stephen M., Boyle, Richard D., Rabbitt, Richard D.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.01.2009; Biophysical Society; The Biophysical Society
• Subjects: Algorithms; Animals; Biochemistry; Biophysical Theory and Modeling; Chinchilla; Cilia - physiology; Cilia - ultrastructure; Computer Simulation; Electric Capacitance; Electric Impedance; Hair Cells, Auditory - physiology; Hair Cells, Auditory - ultrastructure; Hair Cells, Vestibular - physiology; Hair Cells, Vestibular - ultrastructure; Intracellular Space - physiology; Membrane Potentials - physiology; Models, Neurological; Neurons; Patch-Clamp Techniques - methods; Signal transduction; Studies; Turtles
• ISSN: 0006-3495; 1542-0086
• DOI: 10.1529/biophysj.108.137356

Somatic measurements of whole-cell capacitance are routinely used to understand physiologic events occurring in remote portions of cells. These studies often assume the intracellular space is voltage-clamped. We questioned this assumption in auditory and vestibular hair cells with respect to their stereocilia based on earlier studies showing that neurons, with radial dimensions similar to stereocilia, are not always isopotential under voltage-clamp. To explore this, we modeled the stereocilia as passive cables with transduction channels located at their tips. We found that the input capacitance measured at the soma changes when the transduction channels at the tips of the stereocilia are open compared to when the channels are closed. The maximum capacitance is felt with the transducer closed but will decrease as the transducer opens due to a length-dependent voltage drop along the stereocilium length. This potential drop is proportional to the intracellular resistance and stereocilium tip conductance and can produce a maximum capacitance error on the order of fF for single stereocilia and pF for the bundle.