Age-dependent changes in the regulation mechanisms for intracellular calcium ions in ganglion cells of the mouse retina.
The purpose of this study was to investigate the role of intracellular calcium buffering in retinal ganglion cells. We performed a quantitative analysis of calcium homeostasis in ganglion cells of early postnatal and adult mice by simultaneous patch-clamp recordings in sliced tissue and microfluorometric calcium measurements with Fura-2. Endogenous calcium homeostasis was quantified by using the 'added buffer' approach which uses amplitudes and decay time constants of calcium transients to give a standard for intracellular calcium buffering. The recovery phase of depolarization-induced calcium transients was well approximated by a mono-exponential function with a decay time constant that showed a linear dependence on dye concentration. Endogenous calcium binding ratios were found to be 575 (n = 18 cells) in early postnatal and 121 (n = 18 cells) in adult retinal ganglion cells. With respect to ganglion cell degeneration at early postnatal stages, our measurements suggest that neuroprotection of a majority of developing ganglion cells partially results from a specialized calcium homeostasis based on high buffering capacities. Furthermore, the dramatic decrease of the intracellular calcium buffering capacity during ganglion cell development may enhance their vulnerability to neurodegeneration.
Mann
Miriam
M
Department of Ophthalmology II, Augenklinik Abt. II, Forschungsstelle Experimentelle Ophthalmologie, Röntgenweg 11, 72076 Tübingen, Germany.
Haq
Wadood
W
Zabel
Thomas
T
Guenther
Elke
E
Zrenner
Eberhart
E
Ladewig
Thomas
T
D000375:Aging / Q000502:physiology*; D000465:Algorithms; D000818:Animals; D002021:Buffers; D002118:Calcium / Q000502:physiology*; D020013:Calcium Signaling / Q000502:physiology; D004594:Electrophysiology; D006706:Homeostasis / Q000502:physiology; D066298:In Vitro Techniques; D007700:Kinetics; D051379:Mice; D018408:Patch-Clamp Techniques; D012160:Retina / Q000254:growth & development; D012165:Retinal Ganglion Cells / Q000502:physiology*
D002021:Buffers; D002118:Calcium