Role of glia in K+ and pH homeostasis in the neonatal rat spinal cord.
Stimulation-evoked transient changes in extracellular potassium ([K+]e) and pH (pHe) were studied in the neonatal rat spinal cords isolated from 3-13-day-old pups. In unstimulated pups the [K+]e baseline was elevated and pHe was more acid than that in Ringer's solution (3.5 mM K+, pH 7.3-7.35). The [K+]e and pHe in 3-6-day-old pups was 3.91 +/- 0.12 mM and pHe 7.19 +/- 0.01, respectively, while in 10-13-day-old pups it was 4.35 +/- 0.15 mM and 7.11 +/- 0.01, respectively. The [K+]e changes evoked in the dorsal horn by a single electrical stimulus were as large as 1.5-2.5 mM. Such changes in [K+]e are evoked in the adult rat spinal cord with stimulation at a frequency of 10-30 Hz. The maximal changes of 2.1-6.5 mM were found at a stimulation frequency of 10 Hz in 3-6-day-old animals. In older animals the [K+]e changes progressively decreased. The poststimulation K(+)-undershoot was found after a single stimulus as well as after repetitive stimulation. In 3-8-day-old pups, the stimulation evoked an alkaline shift, which was followed by a smaller poststimulation acid shift when the stimulation was discontinued. In pups 3-4-days-old the stimulation evoked the greatest alkaline shifts, i.e., by as much as 0.05 pH units after a single pulse and by about 0.1 pH units during stimulation at a frequency of 10 Hz. In 5-8-day-old pups, the alkaline shift became smaller and the poststimulation acid shift increased.(ABSTRACT TRUNCATED AT 250 WORDS)
Jendelová
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Laboratory of Neurohumoral Regulation, Czechoslovak Academy of Sciences, Prague.
Syková
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D000086:Acetazolamide / Q000494:pharmacology; D000136:Acid-Base Equilibrium / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D000831:Animals, Newborn; D002256:Carbonic Anhydrases / Q000502:physiology; D004558:Electric Stimulation; D005110:Extracellular Space / Q000378:metabolism; D006706:Homeostasis; D006863:Hydrogen-Ion Concentration; D007424:Intracellular Fluid / Q000378:metabolism; D015636:Magnesium Chloride / Q000494:pharmacology; D009457:Neuroglia / Q000502:physiology*; D011188:Potassium / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013116:Spinal Cord / Q000166:cytology* / Q000378:metabolism
D015636:Magnesium Chloride; D002256:Carbonic Anhydrases; D000086:Acetazolamide; D011188:Potassium