title: Elevated cytosolic calcium in the growth cone inhibits neurite elongation in neuroblastoma cells: correlation of behavioral states with cytosolic calcium concentration.
abstract: Schubert (1984) and Kater et al. (1988) have suggested that motility and growth at the neuronal growth cone is activated by an increase of cytosolic free calcium concentration ([Ca2+]i) above the levels found in quiescent growth cones. In order to test this model, we have used a digital imaging fluorescence microscope together with injection of the fluorescent indicator dye Fura-2 to measure [Ca2+]i in growth cones of a mammalian sympathetic neuron, the N1E-115 neuroblastoma cell. The behavior of individual growth cones, together with spontaneously varying levels of [Ca2+]i within the growth cone, were monitored for periods of up to several hours. [Ca2+]i in motile, advancing growth cones was low and equal to [Ca2+]i in quiescent growth cones. Higher values of [Ca2+]i were found in motile growth cones that were not advancing, suggesting that a small elevation of [Ca2+]i inhibits neurite extension. A further rise of [Ca2+]i above the level found in motile, nonadvancing growth cones appeared to inhibit motility and cause retraction of the growth cone back towards the cell body. Spatial gradients of [Ca2+]i within the growth cone were small and, where statistically significant, [Ca2+]i was lower by 5-10 nM in motile regions. Our results are incompatible with the model that a rise of [Ca2+]i is responsible for activating quiescent growth cones; however, our results suggest that in active growth cones [Ca2+]i can regulate morphology and behavior.
authors.affiliation: Department of Physiology, University College London, United Kingdom.
authors.forename: R A
authors.initials: RA
authors.lastname: Silver
authors.forename: A G
authors.initials: AG
authors.lastname: Lamb
authors.forename: S R
authors.initials: SR
authors.lastname: Bolsover
mesh_terms: D000818:Animals; D001369:Axons / Q000648:ultrastructure; D001572:Benzofurans; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D003600:Cytosol / Q000378:metabolism; D005456:Fluorescent Dyes; D016257:Fura-2; D009447:Neuroblastoma; D014407:Tumor Cells, Cultured / Q000166:cytology* / Q000378:metabolism / Q000502:physiology
chemical_list: D001572:Benzofurans; D005456:Fluorescent Dyes; D002118:Calcium; D016257:Fura-2