Characterization of spontaneous calcium transients in nerve growth cones and their effect on growth cone migration.
This study examines the mechanisms of spontaneous and induced [Ca2+]i spiking in nerve growth cones and the effect of spikes on growth cone migration. Over a 10-20 min observation period, 29% of DRG growth cones undergo spontaneous and transient elevations in physiological extracellular Ca2+ ((Ca2+)o; 2 mM), whereas 67% of growth cones exposed to 20 mM (Ca2+)o exhibit similar [Ca2+]i spikes. Spontaneous [Ca2+]i spiking was not observed in neuronal cell bodies or nonneuronal cells. Ca2+ influx through non-voltage-gated Ca2+ channels was required for spontaneous [Ca2+]i spikes in growth cones, since removal of (Ca2+)o, or addition of the general Ca2+ channel blockers La3+ or Ni2+, reversibly blocked [Ca2+]i spiking, while blockers of the voltage-gated Ca2+ channels did not. Experiments using agents that influence intracellular Ca2+ stores suggest that Ca2+ stores may buffer and release Ca2+ during growth cone [Ca2+]i spikes. Growth cone migration was immediately and transiently inhibited by [Ca2+]i spikes, but eventually returned to prespike rates.
Gomez
T M
TM
University of Minnesota, Department of Cell Biology and Neuroanatomy, Minneapolis 55455, USA.
Snow
D M
DM
Letourneau
P C
PC
D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D002642:Chick Embryo; D016257:Fura-2; D005727:Ganglia, Spinal / Q000187:drug effects / Q000648:ultrastructure*; D006801:Humans; D007811:Lanthanum / Q000494:pharmacology; D016501:Neurites / Q000378:metabolism; D009474:Neurons / Q000648:ultrastructure*; D009532:Nickel / Q000494:pharmacology; D012433:Ryanodine / Q000494:pharmacology
D002121:Calcium Channel Blockers; D012433:Ryanodine; D002110:Caffeine; D007811:Lanthanum; D009532:Nickel; D000252:Calcium-Transporting ATPases; D002118:Calcium; D016257:Fura-2