Journal of Neuroscience, Vol 6, 1934-1940, Copyright © 1986 by Society for Neuroscience
Measurements of calcium transients in the soma, neurite, and growth cone of single cultured neurons
SR Bolsover and I Spector
Voltage-gated changes in cytosolic free calcium ion concentration were
measured in single, differentiated cells of mouse neuroblastoma clone
N1E-115 using the calcium-sensitive dye arsenazo III (AIII). In cells
bathed in normal medium containing 10 mM calcium, the changes in AIII
absorbance during a single action potential indicated an increase of 1.4 nM
in cytosolic calcium. When 10 mM tetraethylammonium (TEA) was added to the
bath, the action potential became prolonged and the change in cytosolic
calcium increased to 3.9 nM. Under these conditions, repetitive stimulation
at 0.5 Hz or faster caused a gradual decline in the amplitude and duration
of the action potential and a gradual decline of the change in cytosolic
calcium associated with each action potential. The amplitude of the
prolonged after-hyperpolarization (AHP) that follows the action potential
was found to reflect the magnitude of the change in cytosolic calcium. An
action potential elicited in the cell soma caused an increase in cytosolic
calcium in the soma, neurite, and growth cone regions of a single cell,
indicating that the membrane of all three regions possesses voltage-gated
calcium channels. Estimation of calcium flux per unit area of membrane
suggests a distinct topographical organization of calcium channels. Calcium
channel densities in the growth cone and cell soma regions are similar and
significantly higher than that in the neurite.