Endogenous buffers limit the spread of free calcium in hair cells.
Mobile Ca2+ buffers in hair cells have been postulated to play a dual role. On one hand, they carry incoming Ca2+ away from synaptic areas, allowing synapses to be rapidly reset. On the other hand, they limit the spread of free Ca2+ into the cell, preventing cross-talk between different pathways that employ Ca2+ as a second messenger. We have obtained evidence for such mobile Ca2+ buffers in hair cells by comparing the patterns of Ca2+-induced fluo-3 fluorescence under whole-cell and perforated-patch recording conditions. Fluorescent signals under perforated-patch conditions are relatively weak and are limited to the immediate vicinity of the membrane. These observations can be explained by a diffusion-reaction scheme that, in addition to Ca2+ and fluo-3, incorporates endogenous fixed and mobile Ca2+ buffers. Our experiments also suggest that the mobility of the endogenous buffer might be higher than previously thought. A high buffer mobility is expected to enhance the cell's ability to rapidly modulate transmitter release.
Hall
J D
JD
Department of Physiology, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
Betarbet
S
S
Jaramillo
F
F
D000814:Aniline Compounds; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D004594:Electrophysiology / Q000379:methods; D005456:Fluorescent Dyes; D006198:Hair Cells, Auditory / Q000502:physiology*; D066298:In Vitro Techniques; D007700:Kinetics; D008433:Mathematics; D008959:Models, Neurological; D011894:Rana pipiens; D015290:Second Messenger Systems; D013569:Synapses / Q000502:physiology; D014966:Xanthenes
D000814:Aniline Compounds; D005456:Fluorescent Dyes; D014966:Xanthenes; C059715:Fluo-3; D002118:Calcium