The regulation of pH in the central nervous system

Abstract
The pHi regulation from intracellular acidosis in the central nervous system appears to be mediated by mechanisms driven by the large inwardly directed Na+ gradient. The involvement of these mechanisms in pHi regulation of neurones and glial cells has been investigated in the leech central nervous system using ion-selective microelectrodes. For recovery from acidification, there appear to be three separate mechanisms: Na+/H+ exchange, Na+-dependent Cl/HCO3 exchange, and Na+–HCO3 cotransport. All three mechanisms have a profound effect on the maintenance of pHi homeostasis in glial ceils; whereas in leech neurones, as in other neuronal cells studied previously, the predominant mechanisms are Na+/H+ and Na+-dependent Cl/HCO3 exchange. In addition to acid extrusion mechanisms we also found evidence for Na+-independent Cl/HCO3 exchange. At alkaline pHi this exchanger may mediate some of the pHi recovery from intracellular alkalinization.Key words: central nervous system, pH regulation, neurotransmitter.

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