Dendritic Na+ spikes enable cortical input to drive action potential output from hippocampal CA2 pyramidal neurons

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Abstract

Synaptic inputs from different brain areas are often targeted to distinct regions of neuronal dendritic arbors. Inputs to proximal dendrites usually produce large somatic EPSPs that efficiently trigger action potential (AP) output whereas inputs to distal dendrites are greatly attenuated and may largely modulate AP output. In contrast to most other cortical and hippocampal neurons, hippocampal CA2 pyramidal neurons show unusually strong excitation by their distal dendritic inputs from entorhinal cortex (EC). Here we demonstrate that the ability of these EC inputs to drive CA2 AP output requires the firing of local dendritic Na⁺ spikes. Furthermore we find that CA2 dendritic geometry contributes to the efficient coupling of dendritic Na⁺ spikes to AP output. These results provide a striking example of how dendritic spikes enable direct cortical inputs to overcome unfavorable distal synaptic locale to trigger axonal AP output, and thereby enable efficient cortico-hippocampal information flow.

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Qian Sun

Howard Hughes Medical Institute, Columbia University, New York, United States

For correspondence
qsun79@gmail.com

Competing interests
The authors declare that no competing interests exist.
Kalyan V Srinivas

Howard Hughes Medical Institute, Columbia University, New York, United States

Competing interests
The authors declare that no competing interests exist.
Alaba Sotayo

Howard Hughes Medical Institute, Columbia University, New York, United States

Competing interests
The authors declare that no competing interests exist.
Steven A Siegelbaum

Howard Hughes Medical Institute, Columbia University, New York, United States

Competing interests
The authors declare that no competing interests exist.

Ethics

Animal experimentation: This study was performed in strict accordance with the recommendations in the Guide for the Care and Use of Laboratory Animals of the National Institutes of Health. All mouse studies were approved by the Institutional Animal Care and Use Committee (IACUC) of Columbia University (protocol Number AC-AAAF6104). Animal housing, husbandry, and euthanasia were conducted under the guidelines of the Institute of Comparative Medicine, Columbia University.

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This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.