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Article
Postnatal Development and Activation of L-Type Ca2+ Currents in Locus Ceruleus Neurons: Implications for a Role for Ca2+ in Central Chemosensitivity
Journal of Applied Physiology
  • Ann N. Imber
  • Robert W. Putnam, Wright State University - Main Campus
Document Type
Article
Publication Date
5-15-2012
Abstract
Little is known about the role of Ca2+ in central chemosensitive signaling. We use electrophysiology to examine the chemosensitive responses of tetrodotoxin (TTX)-insensitive oscillations and spikes in neurons of the locus ceruleus (LC), a chemosensitive region involved in respiratory control. We show that both TTX-insensitive spikes and oscillations in LC neurons are sensitive to L-type Ca2+channel inhibition and are activated by increased CO2/H+. Spikes appear to arise from L-type Ca2+ channels on the soma whereas oscillations arise from L-type Ca2+ channels that are distal to the soma. In HEPES-buffered solution (nominal absence of CO2/HCO3−), acidification does not activate either oscillations or spikes. When CO2 is increased while extracellular pH is held constant by elevated HCO3−, both oscillation and spike frequency increase. Furthermore, plots of both oscillation and spike frequency vs. intracellular [HCO3−]show a strong linear correlation. Increased frequency of TTX-insensitive spikes is associated with increases in intracellular Ca2+ concentrations. Finally, both the appearance and frequency of TTX-insensitive spikes and oscillations increase over postnatal agesday 3–16. Our data suggest that 1) L-type Ca2+ currents in LC neurons arise from channel populations that reside in different regions of the neuron, 2) these L-type Ca2+ currents undergo significant postnatal development, and 3) the activity of these L-type Ca2+ currents is activated by increased CO2 through a HCO3−-dependent mechanism. Thus the activity of L-type Ca2+ channels is likely to play a role in the chemosensitive response of LC neurons and may underlie significant changes in LC neuron chemosensitivity during neonatal development.
DOI
10.​1152/​japplphysiol.​01585.​2011
Citation Information
Ann N. Imber and Robert W. Putnam. "Postnatal Development and Activation of L-Type Ca2+ Currents in Locus Ceruleus Neurons: Implications for a Role for Ca2+ in Central Chemosensitivity" Journal of Applied Physiology Vol. 112 Iss. 10 (2012) p. 1715 - 1726 ISSN: 1522-1601
Available at: http://works.bepress.com/robert_putnam/52/