Developmental changes in cell calcium homeostasis during neurogenesis of the embryonic rat cerebral cortex.
We quantified cytoplasmic Ca(2+) (Ca(2+)(c)) levels in cells dissociated from the embryonic (E) rat cortex during neurogenesis. Dual-recordings by flow cytometry using calcium and voltage-sensitive dyes revealed that, at the beginning of cortical development (E11-12), precursor cells exhibited either low (<100 nM), moderate (approximately 250 nM) or high (>1 microM) resting Ca(2+)(c) levels and well-polarized (-70 mV) or less-polarized (-40 mV) resting membrane potentials which reflected postmitotic or proliferative stages of the cell cycle. Ca(2+)(c) levels of all cells included a Ca(2+)(o) entry component, which was also Mn(2+)-permeant in actively proliferating precursors. Postmitotic, but not premitotic, precursors exhibited thapsigargin-sensitive intracellular Ca(2+) (Ca(2+)(i)) stores, which had similar capacities throughout neuronal lineage development. Differentiating neurons, but not precursors expressed Ca(2+)(i) stores with ryanodine and caffeine sensitivity and baseline Ca(2+)(c) levels that depended on Na(+)-Ca(2+) exchange activity. Voltage-dependent Ca(2+)(o) entry was not detected in precursors, but emerged during neuronal differentiation, with most of the neurons expressing functional L-type Ca(2+) channels. Ca(2+) imaging of individually immunoidentified cells acutely recovered in culture confirmed that precursors differentiate into neurons which stereotypically exhibit Ca(2+)(o) entry at the level of the membrane with increased Ca(2+)(i) release mechanisms on Ca(2+)(i) stores, Na(+)-Ca(2+) exchange activity and expression of voltage-dependent Ca(2+) channels.
Maric
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D
Laboratory of Neurophysiology, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA. drangan@codon.nih.gov
Maric
I
I
Barker
J L
JL
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000502:physiology*; D002454:Cell Differentiation; D002540:Cerebral Cortex / Q000196:embryology* / Q000502:physiology; D005314:Embryonic and Fetal Development; D006706:Homeostasis; D007150:Immunohistochemistry; D009474:Neurons / Q000166:cytology / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley
D015220:Calcium Channels; D002118:Calcium