Biphasic effect of calcium on neurite outgrowth in neuroblastoma and cerebellar granule cells.
We have examined the effect of cytosolic calcium concentration ([Ca2+]i) on neurite outgrowth in two neuronal cells, cerebellar granule cells and N1E-115 neuroblastoma cells. The set point [Ca2+]i in unstimulated cells bathed in normal extracellular medium was 37 nM and 108 nM, respectively. When we altered extracellular calcium concentration to cause small excursions of [Ca2+]i either above or below the set point, neurite outgrowth from granule cells declined. Thus granule cells show the bell-shaped dependence of neurite outgrowth on [Ca2+]i characteristic of sensory and other neurones [Dev. Brain Res., 70 (1992) 287-290; The Axon, Oxford University Press, New York, 1994]. In contrast, neurite outgrowth from N1E-115 cells increased monotonically as [Ca2+]i was reduced. This result, which is consistent with results obtained by studying individual growth cones [J. Neurosci., 9 (1989) 4007-4020], implies that these transformed cells are aberrant in having no bell-shaped dependence of neurite outgrowth on [Ca2+]i. In both cell types an increase of [Ca2+]i above the set point reduced neurite outgrowth. However, this decline did not persist as [Ca2+]i was set to increasingly high levels by increasing extracellular calcium. Rather, in both cell types, an increase of extracellular calcium above 6.9 mM produced a second, increasing phase of neurite outgrowth.
Department of Physiology, University College London, UK.
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Zimprich
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Gailey
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Bolsover
D000818:Animals; D001932:Brain Neoplasms / Q000648:ultrastructure*; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology*; D002531:Cerebellum / Q000187:drug effects / Q000648:ultrastructure*; D003600:Cytosol / Q000378:metabolism; D016257:Fura-2; D051379:Mice; D016501:Neurites / Q000187:drug effects / Q000648:ultrastructure*; D009447:Neuroblastoma / Q000648:ultrastructure*; D014407:Tumor Cells, Cultured
D000001:Calcimycin; D002118:Calcium; D016257:Fura-2