Chronaxie measurements in patterned neuronal cultures from rat hippocampus

Shani Stern, Andres Agudelo-Toro, Assaf Rotem, Elisha Moses, Andreas Neef

Research output: Contribution to journalArticlepeer-review


Excitation of neurons by an externally induced electric field is a long standing question that has recently attracted attention due to its relevance in novel clinical intervention systems for the brain. Here we use patterned quasi one-dimensional neuronal cultures from rat hippocampus, exploiting the alignment of axons along the linear patterned culture to separate the contribution of dendrites to the excitation of the neuron from that of axons. Network disconnection by channel blockers, along with rotation of the electric field direction, allows the derivation of strength-duration (SD) curves that characterize the statistical ensemble of a population of cells. SD curves with the electric field aligned either parallel or perpendicular to the axons yield the chronaxie and rheobase of axons and dendrites respectively, and these differ considerably. Dendritic chronaxie is measured to be about 1 ms, while that of axons is on the order of 0.1 ms. Axons are thus more excitable at short time scales, but at longer time scales dendrites are more easily excited. We complement these studies with experiments on fully connected cultures. An explanation for the chronaxie of dendrites is found in the numerical simulations of passive, realistically structured dendritic trees under external stimulation. The much shorter chronaxie of axons is not captured in the passive model and may be related to active processes. The lower rheobase of dendrites at longer durations can improve brain stimulation protocols, since in the brain dendrites are less specifically oriented than axonal bundles, and the requirement for precise directional stimulation may be circumvented by using longer duration fields.

Original languageEnglish
Article number132577
JournalPLoS ONE
Issue number7
StatePublished - 17 Jul 2015
Externally publishedYes

Bibliographical note

Funding Information:
The authors thank Ofer Feinerman for useful discussions and for permission to use images of 1D neurons. We thank Fred Wolf, Menahem Segal and Eitan Reuveny for very helpful discussions. This work was partly funded by the German Ministry for Education and Research through the Bernstein Focus Neurotechnology Göttingen (01GQ0811, 01GQ0810) and partly by the Göttingen Graduate School for Neurosciences, Biophysics und Molecular Biosciences (DFG Grant GSC 226/1). This research was also supported by the Minerva Foundation, the Ministry of Science and Technology, Israel, and by Israel Science Foundation grant 1320/09 and the Bi-National Science Foundation grant 2008331.

Publisher Copyright:
Copyright: © 2015 Stern et al.

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