HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Church, J Articles by McLennan, H Search for Related Content PubMed PubMed Citation Articles by Church, J Articles by McLennan, H

Department of Physiology, University of British Columbia, Vancouver, Canada.

1. Intracellular recordings were made from the somata of CA1b hippocampal pyramidal neurones in vitro and the concentration of bicarbonate ion ([HCO3-]o) in the artificial cerebrospinal fluid (ACSF) was varied by substitution for Cl-. 2. Reducing [HCO3-]o from 26 mM (standard ACSF) to 8.6 mM or raising it to 72 mM had only minor effects on resting membrane potential but input resistance was reduced and increased, respectively. Threshold for Na(+)-dependent action potential generation was raised during the perfusion with low-HCO3- ACSF and lowered during perfusion with high-HCO3- ACSF. In tetrodotoxin-poisoned neurones where presumed Ca2(+)-dependent potentials could be elicited in standard ACSF, perfusion with high-HCO3- ACSF lowered the activation threshold. Where no Ca2(+)-dependent spikes could be elicited in standard ACSF, perfusion with high-HCO3- ACSF caused their appearance. Ca2(+)-dependent spikes could not be evoked during perfusion with low-HCO3- ACSF. 3. Depolarizing current pulses evoked two basic patterns of action potential discharge under standard [HCO3-]o conditions. Conversion between the two types was possible by varying [HCO3-]o. In those neurones which fired a train of fast Na(+)-dependent spikes in standard ACSF, perfusion with high-HCO3- ACSF usually led to the development of burst discharges. A smaller number of neurones responded to depolarizing current with an initial burst of three to six action potentials; the bursts were attenuated in low-HCO3- ACSF and replaced by a repetitive spike discharge. Frequency accommodation of spike discharge in response to depolarizing current pulses and the after-hyperpolarization following a current-evoked discharge were usually both attenuated in low-HCO3- ACSF and enhanced in high-HCO3- ACSF. 4. Orthodromically evoked excitatory postsynaptic potentials (EPSPs) and early and late inhibitory postsynaptic potentials (IPSPs) were reduced in amplitude during perfusion with low-HCO3- ACSF. In high-HCO3- ACSF, EPSP amplitude and duration increased, the latter reflecting a positive shift in the reversal potential of the early IPSP consequent upon reduced [Cl-] in high-HCO3- ACSF. The late IPSP was, however, unaffected. 5. Responses to ionophoretically applied excitatory amino acids were enhanced in high-HCO3- ACSF and depressed in low-HCO3- ACSF. 6. Perfusion with high-HCO3- ACSF was associated with the development of epileptiform activity. Spontaneous or synaptically evoked bursts of action potentials were indistinguishable and could be blocked by N-methyl-D-aspartate antagonists.(ABSTRACT TRUNCATED AT 400 WORDS)

This article has been cited by other articles:

				T. Kelly and J. Church Relationships Between Calcium and pH in the Regulation of the Slow Afterhyperpolarization in Cultured Rat Hippocampal Neurons J Neurophysiol, November 1, 2006; 96(5): 2342 - 2353. [Abstract] [Full Text] [PDF]

				X. Q. Gu, J. Xue, and G. G. Haddad Effect of chronically elevated CO2 on CA1 neuronal excitability Am J Physiol Cell Physiol, September 1, 2004; 287(3): C691 - C697. [Abstract] [Full Text] [PDF]

				T. Kelly and J. Church pH modulation of currents that contribute to the medium and slow afterhyperpolarizations in rat CA1 pyramidal neurones J. Physiol., January 15, 2004; 554(2): 449 - 466. [Abstract] [Full Text] [PDF]

				C. Bruehl and O. W. Witte Relation Between Bicarbonate Concentration and Voltage Dependence of Sodium Currents in Freshly Isolated CA1 Neurons of the Rat J Neurophysiol, May 1, 2003; 89(5): 2489 - 2498. [Abstract] [Full Text] [PDF]

				C. Bruehl, W. J. Wadman, and O. W. Witte Concentration Dependence of Bicarbonate-Induced Calcium Current Modulation J Neurophysiol, November 1, 2000; 84(5): 2277 - 2283. [Abstract] [Full Text] [PDF]

				M. de Curtis, A. Manfridi, and G. Biella Activity-Dependent pH Shifts and Periodic Recurrence of Spontaneous Interictal Spikes in a Model of Focal Epileptogenesis J. Neurosci., September 15, 1998; 18(18): 7543 - 7551. [Abstract] [Full Text] [PDF]