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Activity-related changes in intracellular pH in rat thalamic relay neurons

Meyer, Torsten Michael1; Munsch, Thomas1,2; Pape, Hans-Christian1

Neurophysiology, Basic and Clinical

Activity-related shifts in intracellular pH (pHi) can exert potent neuromodulatory actions. Different states of neuronal activity of thalamocortical neurons were found to differentially modulate pHi. Tonic activity evoked by injection of depolarizing current led to a reversible rise in [H+]i which was nearly abolished in the presence of TTX. Block of voltage-gated calcium channels with 1 mM Ni2+ reduced the [H+]i transients related to tonic activity. Rhythmic activation of burst discharges caused changes of [H+]i which were decreased by TTX, whereas 1 mM Ni2+ almost abolished the [H+]i transients. The present results show that different forms of neuronal activity can lead to intracellular acidification caused by different mechanisms, i.e. Na+ and Ca2+ influx through sodium and Ca2+ channels, respectively, and the subsequent activation of a Ca2+/H+ pump. The resulting acidosis is suggested to reduce further Ca2+ influx and prevent excessive neuronal excitation.

1Institut für Physiologie, Medizinische Fakultät, Otto-von-Guericke Universität, Leipziger Str. 44, D-39120 Magdeburg, Germany

2Corresponding Author: Thomas Munsch

Acknowledgements: This work was supported by the Deutsche Forschungsgemeinschaft (Pa 336/13-1). Thanks are due to Dr T. Budde for comments on the manuscript.

Received 8 September 1999; accepted 20 October 1999

© 2000 Lippincott Williams & Wilkins, Inc.