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Clin Neurophysiol. 2009 Jun;120(6):1161-7. doi: 10.1016/j.clinph.2009.01.022. Epub 2009 Apr 28.

Safety limits of cathodal transcranial direct current stimulation in rats.

Author information

1
Department of Clinical Neurophysiology, University Medical Center Göttingen, Robert-Koch-Strasse 40, 37099 Göttingen, Germany. dliebet@gwdg.de

Abstract

OBJECTIVE:

The aim of this rat study was to investigate the safety limits of extended transcranial direct current stimulation (tDCS). tDCS may be of therapeutic value in several neuro-psychiatric disorders. For its clinical applicability, however, more stable effects are required, which may be induced by intensified stimulations.

METHODS:

Fifty-eight rats received single cathodal stimulations at 1-1000 microA for up to 270 min through an epicranial electrode (3.5 mm(2)). Histological evaluation (H&E) was performed 48 h later. A threshold estimate was calculated from volumes of DC-induced lesions.

RESULTS:

Brain lesions occurred at a current density of 142.9 A/m(2) for durations greater than 10 min. For current densities between 142.9 and 285.7 A/m(2), lesion size increased linearly with charge density; with a calculated zero lesion size intercept of 52,400 C/m(2). Brains stimulated below either this current density or charge density threshold, including stimulations over 5 consecutive days, were morphologically intact.

CONCLUSION:

The experimentally determined threshold estimate is two orders of magnitude higher than the charge density currently applied in humans (171-480 C/m(2)). In relation to transcranial DC stimulation in humans the rat epicranial electrode montage may provide for an additional safety margin.

SIGNIFICANCE:

Although these results cannot be directly transferred to humans, they encourage the development intensified tDCS protocols. Further animal studies are required, before such protocols can be applied in humans.

PMID:
19403329
DOI:
10.1016/j.clinph.2009.01.022
[Indexed for MEDLINE]

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