Intracellular pH regulation in neurons from chemosensitive and nonchemosensitive areas of the medulla.
Intracellular pH (pHi) regulation was studied in neurons from two chemosensitive [nucleus of the solitary tract (NTS) and ventrolateral medulla (VLM)] and two nonchemosensitive [hypoglossal (Hyp) and inferior olive (IO)] areas of the medulla oblongata. Intrinsic buffering power (betaint) was the same in neurons from all regions (46 mM/pH U). Na+/H+ exchange mediated recovery from acidification in all neurons [Ritucci, N. A., J. B. Dean, and R. W. Putnam. Am. J. Physiol. 273 (Regulatory Integrative Comp. Physiol. 42): R433-R441, 1997]. Cl-/HCO-3 exchange mediated recovery from alkalinization in VLM, Hyp, and IO neurons but was absent from most NTS neurons. The Na+/H+ exchanger from NTS and VLM neurons was fully inhibited when extracellular pH (pHo) <7.0, whereas the exchanger from Hyp and IO neurons was fully inhibited only when pHo <6.7. The Cl-/HCO-3 exchanger from VLM, but not Hyp and IO neurons, was inhibited by pHo of 7.9. These pH regulatory properties resulted in steeper pHi-pHo relationships in neurons from chemosensitive regions compared with those from nonchemosensitive regions. These differences are consistent with a role for changes of pHi as the proximate signal in central chemoreception and changes of pHo in modulating pHi changes.
Department of Physiology and Biophysics, Wright State University, Dayton, Ohio 45435, USA.
N A
NA
Ritucci
L
L
Chambers-Kersh
J B
JB
Dean
R W
RW
Putnam
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D005452:Fluoresceins; D011422:Propionates; D000643:Ammonium Chloride; C057433:2',7'-bis-(2-carboxyethyl)-5(6)-carboxyfluorescein acetoxymethyl ester; D000584:Amiloride; C029658:propionic acid; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid