Effects of uniform extracellular DC electric fields on excitability in rat hippocampal slices in vitro

Marom Bikson, M Inoue, H Akiyama, Jacqueline Deans, John Fox, H Miyakawa, John Jefferys

Research output: Contribution to journalArticle

438 Citations (Scopus)

Abstract

The effects of uniform steady state (DC) extracellular electric fields on neuronal excitability were characterized in rat hippocampal slices using field, intracellular and voltage-sensitive dye recordings. Small electric fields (<\40\ mV mm(-1)), applied parallel to the somato-dendritic axis, induced polarization of CA1 pyramidal cells; the relationship between applied field and induced polarization was linear (0.12 +/- 0.05 mVper mV mm(-1) average sensitivity at the soma). The peak amplitude and time constant (15-70 ms) of membrane polarization varied along the axis of neurons with the maximal polarization observed at the tips of basal and apical dendrites. The polarization was biphasic in the mid-apical dendrites; there was a time-dependent shift in the polarity reversal site. DC fields altered the thresholds of action potentials evoked by orthodromic stimulation, and shifted their initiation site along the apical dendrites. Large electric fields could trigger neuronal firing and epileptiform activity, and induce long-term (> 1 s) changes in neuronal excitability. Electric fields perpendicular to the apical-dendritic axis did not induce somatic polarization, but did modulate orthodromic responses, indicating an effect on afferents. These results demonstrate that DC fields can modulate neuronal excitability in a time-dependent manner, with no clear threshold, as a result of interactions between neuronal compartments, the non-linear properties of the cell membrane, and effects on afferents.
Original languageEnglish
Pages (from-to)175-190
Number of pages16
JournalThe Journal of Physiology
Volume557
Issue number1
Early online date19 Mar 2004
DOIs
Publication statusPublished - 19 Mar 2004

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