Changes in mitochondrial status associated with altered Ca2+ homeostasis in aged cerebellar granule neurons in brain slices.
In the present work, we investigated the relationship between mitochondrial function and Ca2+ homeostasis in brain slices obtained from mice that aged normally. In acute preparations, the cerebellar neurons had similar values for intracellular free Ca2+ ([Ca2+]i) regardless of their age (range, 6 weeks to 24 months). However, compared with the young slices, the aged neurons (20-24 months) showed an enhanced rate of [Ca2+]i increases as a function of the time the slices were maintained in vitro. When slices were stimulated (KCl depolarization), there were significant differences in the patterns of [Ca2+]i signal displayed by the young and old cerebellar granule neurons. More importantly, the aged neurons showed a significant delay in their capacity to recover the resting [Ca2+]i. The relationship between [Ca2+]i and mitochondrial membrane potential was assessed by recording both parameters simultaneously, using fura-2 and rhodamine-123. In both young and aged neurons, the cytosolic [Ca2+]i signal was associated with a mitochondrial depolarization response. In the aged neurons, the mitochondria had a significantly longer repolarization response, and quantitative analysis showed a direct correlation between the delays in mitochondrial repolarization and [Ca2+]i recovery, indicating the causal relationship between the two parameters. Thus, the present results show that the reported changes in Ca2+ homeostasis associated with aging, which manifest principally in a decreased capacity of maintaining a stable resting [Ca2+]i or recovering the resting [Ca2+]i values after stimulation, are primarily attributable to a metabolic dysfunction in which the mitochondrial impairment plays an important role.
Xiong
Jie
J
Department of Physiology, Division of Medical Sciences, University of Birmingham, Edgbaston B15 2TT, United Kingdom.
Verkhratsky
Alex
A
Toescu
Emil C
EC
D000375:Aging; D000818:Animals; D001921:Brain / Q000166:cytology; D002118:Calcium / Q000032:analysis*; D002478:Cells, Cultured; D002531:Cerebellum / Q000737:chemistry / Q000166:cytology* / Q000502:physiology; D005456:Fluorescent Dyes; D006706:Homeostasis; D066298:In Vitro Techniques; D008564:Membrane Potentials; D051379:Mice; D008810:Mice, Inbred C57BL; D008928:Mitochondria / Q000737:chemistry / Q000502:physiology*; D009474:Neurons / Q000737:chemistry / Q000187:drug effects / Q000502:physiology*; D018408:Patch-Clamp Techniques; D011189:Potassium Chloride / Q000494:pharmacology; D020112:Rhodamine 123
D005456:Fluorescent Dyes; D020112:Rhodamine 123; D011189:Potassium Chloride; D002118:Calcium