Dendritic integration of excitatory inputs on hippocampal interneuron dendrites
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1
Hungarian Academy of Sciences, Institute of Experimental Medicine, Hungary
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2
University of Szeged, Research Group for Cortical Microcircuits of the Hungarian Academy of Sciences, Department of Physiology, Anatomy and Neuroscience, Hungary
Although dendritic processes of hippocampal CA1 interneurons receive a vast number of excitatory inputs, little is known on how the arising excitatory postsynaptic potentials (EPSPs) are integrated within single dendritic branches. We used multisite focal extracellular stimulation and glutamate uncaging to deliver different spatiotemporal input patterns to single dendritic branches of hippocampal CA1 stratum radiatum interneurons. The evoked EPSPs were simultaneously recorded with the two-photon imaging of local dendritic calcium signals. We used a novel rapid two-photon linescan technique in order to measure long dendritic segments (typically > 30 µm). Freehand lines were placed following the curvature of single long dendritic segments to monitor the calcium signals elicited by focal electric stimulation (elicited by two electrodes, located at different relative distances). The scanning time being in the range of less then 6 milliseconds or less allowed us to analyze the spatiotemporal properties of calcium compartments. Appropriately timed and sized input patterns produced a supralinear summation of local calcium signals, and somatically recorded EPSPs showed similar characteristics. We have also studied the spatiotemporal characteristics of signal integration by using two-photon photoactivation by MNI-glutamate uncaging. By registering the input/output characteristics of interneuron dendrites, we observed dendritic NMDA-spikes (Schiller et al., 2004) that appeared after activating on average 15.8 clustered inputs synchronously. When inputs were more distributed on a single branch, no dSpikes appeared. Our results suggest that similarly to pyramidal neurons the aspiny dendrites of hippocampal interneurons summate inputs nonlinearly.
Conference:
IBRO International Workshop 2010, Pécs, Hungary, 21 Jan - 23 Jan, 2010.
Presentation Type:
Poster Presentation
Topic:
Cellular neuroscience
Citation:
Szadai
Z,
Kaszás
A,
Turi
GF,
Vágvölgyi
A,
Szalay
G,
Tamás
G,
Éva
T,
Vizi
SE and
Rózsa
B
(2010). Dendritic integration of excitatory inputs on hippocampal interneuron dendrites.
Front. Neurosci.
Conference Abstract:
IBRO International Workshop 2010.
doi: 10.3389/conf.fnins.2010.10.00138
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Received:
28 Apr 2010;
Published Online:
28 Apr 2010.
*
Correspondence:
Zoltán Szadai, Hungarian Academy of Sciences, Institute of Experimental Medicine, Budapest, Hungary, szadaiz@gmail.com