Advertisement

Intrinsic Chemosensitivity of Individual Nucleus Tractus Solitarius (NTS) and Locus Coeruleus (LC) Neurons from Neonatal Rats

  • Nicole L. Nichols
  • Lynn K. Hartzler
  • Susan C. Conrad
  • Jay B. Dean
  • Robert W. Putnam
Part of the Advances in Experimental Medicine and Biology book series (AEMB, volume 605)

Chemosensitive (CS) neurons are found in discrete brainstem regions, but whether the CS response of these neurons is due to intrinsic chemosensitivity of individual neurons or is mediated by changes in chemical and/or electrical synaptic input is largely unknown. We studied the effect of synaptic blockade (11.4 mM Mg2+/0.2 mM Ca2+) solution (SNB) and a gap junction uncoupling agent carbenoxolone (CAR—100 μM) on the response of neurons from two CS brainstem regions, the NTS and the LC. In NTS neurons, SNB decreased spontaneous firing rate (FR). We calculated the magnitude of the FR response to hypercapnic acidosis (HA; 15% CO2) using the Chemosensitivity Index (CI). The percentage of NTS neurons activated and CI were the same in the absence and presence of SNB. Blocking gap junctions with CAR did not significantly alter spontaneous FR. CAR did not alter the CI in NTS neurons and resulted in a small decrease in the percentage of activated neurons, which was most evident in NTS neurons from rats younger than postnatal day 10. In LC neurons, SNB resulted in an increase in spontaneous FR. As with NTS neurons, SNB did not alter the percentage of activated neurons or the CI in LC neurons. CAR resulted in a small increase in spontaneous FR in LC neurons.

Keywords

Firing Rate Locus Coeruleus Locus Coeruleus Neuron Hypercapnic Acidosis Spontaneous Firing Rate 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. Ballantyne, D., Andrzejewski, M., Mückenhoff K. and Scheid, P. (2004) Rhythms, synchrony and electrical coupling in the locus coeruleus. Respir. Physiol. Neurobiol. 143, 199–214.CrossRefPubMedGoogle Scholar
  2. Ballantyne, D. and Scheid, P. (2000) Mammalian brainstem chemosensitive neurones: linking them to respiration in vitro. J. Physiol., London 525, 567–572.CrossRefPubMedGoogle Scholar
  3. Conrad, S.C., Mulkey, D.K., Ritucci, N.A., Dean, J.B. and Putnam, R.W. (2005) Development of chemosensitivity in neurons from the nucleus tractus solitarius (NTS). FASEB J. 19, A649.Google Scholar
  4. Dean, J.B., Ballantyne, D., Cardone, D.L., Erlichman, J.S. and Solomon, I.C. (2002) Role of gap junctions in CO2 chemoreception and respiratory control. Am. J. Physiol. Lung Cell Mol. Physiol. 283, L665–L670.PubMedGoogle Scholar
  5. Dean, J.B., Bayliss, D.A., Erickson, J.T., Lawing, W.L. and Milhorn, D.E. (1990) Depolarization and stimulation of neurons in nucleus tractus solitarii by carbon dioxide does not require chemical synaptic input. Neuroscience 36, 207–216.CrossRefPubMedGoogle Scholar
  6. Dean, J.B., Huang, R.-Q., Erlichman, J.S., Southard, T.L. and Hellard, D.T. (1997) Cell-cell coupling occurs in dorsal medullary neurons after minimizing anatomical-coupling artifacts. Neuroscience 80, 21–40.CrossRefPubMedGoogle Scholar
  7. Dean, J.B., Kinkade, E.A. and Putnam, R.W. (2001) Cell-cell coupling in CO2/H+-excited neurons in brainstem slices. Respir. Physiol. 129, 83–100.CrossRefPubMedGoogle Scholar
  8. Filosa, J.A., Dean, J.B. and Putnam, R.W. (2002) Role of intracellular and extracellular pH in the chemosensitive response of rat locus coeruleus neurones. J. Physiol., London 541, 493–509.CrossRefPubMedGoogle Scholar
  9. Filosa, J.A. and Putnam, R.W. (2003) Multiple targets of chemosensitive signaling in locus coeruleus neurons: role of K+ and Ca2+ channels. Am. J. Physiol. Cell Physiol. 284, C145–C155.PubMedGoogle Scholar
  10. Huang, R.-Q., Erlichman, J.S. and Dean, J.B. (1997) Cell-cell coupling between CO2-excited neurons in the dorsal medulla oblongata. Neuroscience 80, 41–57.CrossRefPubMedGoogle Scholar
  11. Oyamada, Y., Ballantyne, D., Mückenhoff, K. and Scheid, P. (1998) Respiration-modulated membrane potential and chemosensitivity of locus coeruleus neurones in the in vitro brainstem-spinal cord of the neonatal rat. J. Physiol., London 513, 318–398.CrossRefGoogle Scholar
  12. Solomon, I.C. and Dean, J.B. (2002) Gap junctions in CO2-chemoreception and respiratory control. Respir. Physiol. Neurobiol. 131, 155–173.CrossRefPubMedGoogle Scholar
  13. Wang, W., Pizzonia, J.J. and Richerson, G.B. (1998) Chemosensitivity of rat medullary raphé neurones in primary tissue culture. J. Physiol., London 511, 433–450.CrossRefPubMedGoogle Scholar

Copyright information

© Springer 2008

Authors and Affiliations

  • Nicole L. Nichols
  • Lynn K. Hartzler
  • Susan C. Conrad
  • Jay B. Dean
  • Robert W. Putnam

There are no affiliations available

Personalised recommendations