Photometric recording of transmembrane potential in outer hair cells

摘要: Cochlear outer hair cells (OHCs) are polarized epithelial that have mechanoelectrical transduction channels within their apical stereocilia and produce electromotile force along lateral wall. Phase shifts, or time delays, in the transmembrane voltage occurring at different axial locations cell may contribute to our understanding of how these operate auditory frequencies. We developed a method optically measure phase OHC potential using voltage-sensitive dye (VSD) di-8-ANEPPS. The exit aperture fibre-optic light source was driven two dimensions so 24 microm spot excitation could be positioned length OHC. used whole-cell patch-clamp technique current-clamp mode stimulate base. photometric response were monitored with photodetector amplifier, respectively. regional changes membrane maintained (dc) sinusoidal (ac) current stimuli applied base cell. neutral density filter lower intensity reduce phototoxicity. A sensitive detector lock-in amplifier small ac VSD signal. This permitted measurements below noise floor static fluorescence. amplitude components recorded for up 800 Hz. data 400-800 Hz show presence delay between stimulus local measured Results consistent hypothesis OHCs exhibit inhomogeneous potentials vary position analogy nerve axons.