HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 289/3/R851    most recent 00132.2005v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (14) Citing Articles via Google Scholar Google Scholar Articles by Ritucci, N. A. Articles by Putnam, R. W. Search for Related Content PubMed PubMed Citation Articles by Ritucci, N. A. Articles by Putnam, R. W.

NEUROHUMORAL CONTROL OF CARDIOVASCULAR FUNCTION

Response of membrane potential and intracellular pH to hypercapnia in neurons and astrocytes from rat retrotrapezoid nucleus

¹Department of Neuroscience, Cell Biology and Physiology, Wright State University School of Medicine, Dayton, Ohio; ²Department of Biology, St. Lawrence University, Canton, New York; and ³Department of Physiology, Dartmouth Medical School, Lebanon, New Hampshire

Submitted 23 February 2005 ; accepted in final form 13 May 2005

We compared the response to hypercapnia (10%) in neurons and astrocytes among a distinct area of the retrotrapezoid nucleus (RTN), the mediocaudal RTN (mcRTN), and more intermediate and rostral RTN areas (irRTN) in medullary brain slices from neonatal rats. Hypercapnic acidosis (HA) caused pH_o to decline from 7.45 to 7.15 and a maintained intracellular acidification of 0.15 ± 0.02 pH unit in 90% of neurons from both areas (n = 16). HA excited 44% of mcRTN (7/16) and 38% of irRTN neurons (6/16), increasing firing rate by 167 ± 75% (chemosensitivity index, CI, 256 ± 72%) and 310 ± 93% (CI 292 ± 50%), respectively. These responses did not vary throughout neonatal development. We compared the responses of mcRTN neurons to HA (decreased pH_i and pH_o) and isohydric hypercapnia (IH; decreased pH_i with constant pH_o). Neurons excited by HA (firing rate increased 156 ± 46%; n = 5) were similarly excited by IH (firing rate increased 167 ± 38%; n = 5). In astrocytes from both RTN areas, HA caused a maintained intracellular acidification of 0.17 ± 0.02 pH unit (n = 6) and a depolarization of 5 ± 1 mV (n = 12). In summary, many neurons (42%) from the RTN are highly responsive (CI 248%) to HA; this may reflect both synaptically driven and intrinsic mechanisms of CO₂ sensitivity. Changes of pH_i are more significant than changes of pH_o in chemosensory signaling in RTN neurons. Finally, the lack of pH_i regulation in response to HA suggests that astrocytes do not enhance extracellular acidification during hypercapnia in the RTN.

brain stem; chemosensitivity; extracellular pH; glia; ventilatory control

This article has been cited by other articles:

				A. E. Kersh, L. K. Hartzler, K. Havlin, B. B. Hubbell, V. Nanagas, A. Kalra, J. Chua, R. Whitesell, N. A. Ritucci, J. B. Dean, et al. pH regulating transporters in neurons from various chemosensitive brainstem regions in neonatal rats Am J Physiol Regulatory Integrative Comp Physiol, November 1, 2009; 297(5): R1409 - R1420. [Abstract] [Full Text] [PDF]

				J. S. Erlichman, A. C. Boyer, P. Reagan, R. W. Putnam, N. A. Ritucci, and J. C. Leiter Chemosensory Responses to CO2 in Multiple Brain Stem Nuclei Determined Using a Voltage-Sensitive Dye in Brain Slices From Rats J Neurophysiol, September 1, 2009; 102(3): 1577 - 1590. [Abstract] [Full Text] [PDF]

				N. L. Nichols, D. K. Mulkey, K. A. Wilkinson, F. L. Powell, J. B. Dean, and R. W. Putnam Characterization of the chemosensitive response of individual solitary complex neurons from adult rats Am J Physiol Regulatory Integrative Comp Physiol, March 1, 2009; 296(3): R763 - R773. [Abstract] [Full Text] [PDF]

				S. M. Johnson, M. A. Haxhiu, and G. B. Richerson GFP-expressing locus ceruleus neurons from Prp57 transgenic mice exhibit CO2/H+ responses in primary cell culture J Appl Physiol, October 1, 2008; 105(4): 1301 - 1311. [Abstract] [Full Text] [PDF]

				T. S. Moreira, A. C. Takakura, E. Colombari, and P. G. Guyenet Activation of 5-Hydroxytryptamine Type 3 Receptor-Expressing C-Fiber Vagal Afferents Inhibits Retrotrapezoid Nucleus Chemoreceptors in Rats J Neurophysiol, December 1, 2007; 98(6): 3627 - 3637. [Abstract] [Full Text] [PDF]

				H. Kiwull-Schone, P. Kiwull, S. Frede, and M. Wiemann Role of Brainstem Sodium/Proton Exchanger 3 for Breathing Control during Chronic Acid Base Imbalance Am. J. Respir. Crit. Care Med., September 1, 2007; 176(5): 513 - 519. [Abstract] [Full Text] [PDF]

				T. S. Moreira, A. C. Takakura, E. Colombari, G. H. West, and P. G. Guyenet Inhibitory input from slowly adapting lung stretch receptors to retrotrapezoid nucleus chemoreceptors J. Physiol., April 1, 2007; 580(1): 285 - 300. [Abstract] [Full Text] [PDF]

				J. Su, L. Yang, X. Zhang, A. Rojas, Y. Shi, and C. Jiang High CO2 chemosensitivity versus wide sensing spectrum: a paradoxical problem and its solutions in cultured brainstem neurons J. Physiol., February 1, 2007; 578(3): 831 - 841. [Abstract] [Full Text] [PDF]

				D. K. Mulkey, A. M. Mistry, P. G. Guyenet, and D. A. Bayliss Purinergic P2 receptors modulate excitability but do not mediate pH sensitivity of RTN respiratory chemoreceptors. J. Neurosci., July 5, 2006; 26(27): 7230 - 7233. [Abstract] [Full Text] [PDF]

				A. C. T. Takakura, T. S. Moreira, E. Colombari, G. H. West, R. L. Stornetta, and P. G. Guyenet Peripheral chemoreceptor inputs to retrotrapezoid nucleus (RTN) CO2-sensitive neurons in rats J. Physiol., April 15, 2006; 572(2): 503 - 523. [Abstract] [Full Text] [PDF]

				P. G. Guyenet, D. K. Mulkey, R. L. Stornetta, and D. A. Bayliss Regulation of Ventral Surface Chemoreceptors by the Central Respiratory Pattern Generator J. Neurosci., September 28, 2005; 25(39): 8938 - 8947. [Abstract] [Full Text] [PDF]