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.
Ritucci
N A
NA
Department of Physiology and Biophysics, Wright State University, Dayton, Ohio 45435, USA.
Chambers-Kersh
L
L
Dean
J B
JB
Putnam
R W
RW
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000584:Amiloride / Q000494:pharmacology*; D000643:Ammonium Chloride / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D002628:Chemoreceptor Cells / Q000187:drug effects / Q000502:physiology*; D005452:Fluoresceins; D006706:Homeostasis; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007700:Kinetics; D008526:Medulla Oblongata / Q000187:drug effects / Q000502:physiology*; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D011422:Propionates / Q000494:pharmacology; D051381:Rats; D017552:Solitary Nucleus / Q000502:physiology*
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