Heterogeneous patterns of pH regulation in glial cells in the dorsal and ventral medulla
1 Department of Biology, St. Lawrence University, Canton, New York 13615; and 2 Departments of Physiology and Medicine, Dartmouth Medical School, Lebanon, New Hampshire 03756 Submitted 6 May 2003 ; accepted in final form 27 September 2003 We examined pH regulation in two chemosensitive areas of the...
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Veröffentlicht in: | American journal of physiology. Regulatory, integrative and comparative physiology integrative and comparative physiology, 2004-02, Vol.286 (2), p.289-R302 |
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Zusammenfassung: | 1 Department of Biology, St. Lawrence University, Canton, New York 13615; and 2 Departments of Physiology and Medicine, Dartmouth Medical School, Lebanon, New Hampshire 03756
Submitted 6 May 2003
; accepted in final form 27 September 2003
We examined pH regulation in two chemosensitive areas of the brain, the retrotrapezoid nucleus (RTN) and the nucleus tractus solitarius (NTS), to identify the proton transporters involved in regulation of intracellular pH (pH i ) in medullary glia. Transverse brain slices from young rats [postnatal day 8 (P8) to P20] were loaded with the pH-sensitive probe 2',7'-bis (2-carboxyethyl)-5,6-carboxyfluorescein after kainic acid treatment removed neurons. Cells were alkalinized when they were depolarized (extracellular K + increased from 6.24 to 21.24 mM) in the RTN but not in the NTS. This alkaline shift was inhibited by 0.5 mM DIDS. Removal of or Na + from the perfusate acidified the glial cells, but the acidification after Na + removal was greater in the RTN than in the NTS. Treatment of the slice with 5-( N -ethyl- N -isopropyl)amiloride (100 µM) in saline containing acidified the cells in both nuclei, but the acidification was greater in the NTS. Restoration of extracellular Cl - after Cl - depletion during the control condition acidified the cells. Immunohistochemical studies of glial fibrillary acid protein demonstrated much denser staining in the RTN compared with the NTS. We conclude that there is evidence of cotransport and Na + /H + exchange in glia in the RTN and NTS, but the distribution of glia and the distribution of these pH-regulatory functions are not identical in the NTS and RTN. The differential strength of glial pH regulatory function in the RTN and NTS may also alter CO 2 chemosensory neuronal function at these two chemosensitive sites in the brain stem.
astrocytes; central chemosensitivity; respiratory control
Address for reprint requests and other correspondence: J. S. Erlichman, Dept. of Biology, St. Lawrence Univ., Canton, NY 13617 (E-mail: jerlichman{at}stlawu.edu ). |
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ISSN: | 0363-6119 1522-1490 |
DOI: | 10.1152/ajpregu.00245.2003 |