S. Zhao and D. Studer contributed equally to this work.
Structural plasticity of hippocampal mossy fiber synapses as revealed by high-pressure freezing
Article first published online: 14 MAY 2012
Copyright © 2012 Wiley Periodicals, Inc.
Journal of Comparative Neurology
Volume 520, Issue 11, pages 2340–2351, 1 August 2012
How to Cite
Zhao, S., Studer, D., Chai, X., Graber, W., Brose, N., Nestel, S., Young, C., Rodriguez, E. P., Saetzler, K. and Frotscher, M. (2012), Structural plasticity of hippocampal mossy fiber synapses as revealed by high-pressure freezing. J. Comp. Neurol., 520: 2340–2351. doi: 10.1002/cne.23040
- Issue published online: 14 MAY 2012
- Article first published online: 14 MAY 2012
- Accepted manuscript online: 11 JAN 2012 07:23AM EST
- Manuscript Accepted: 7 JAN 2012
- Manuscript Revised: 17 NOV 2011
- Manuscript Received: 30 AUG 2011
- Deutsche Forschungsgemeinschaft. Grant Number: SFB 780
- Swiss National Foundation. Grant Number: 3100AO_118394
- Michael Frotscher is Senior Research Professor of the Hertie Foundation
- synaptic ultrastructure;
- hippocampal mossy fibers;
- CA3 pyramidal cells;
- long-term potentiation
Despite recent progress in fluorescence microscopy techniques, electron microscopy (EM) is still superior in the simultaneous analysis of all tissue components at high resolution. However, it is unclear to what extent conventional fixation for EM using aldehydes results in tissue alteration. Here we made an attempt to minimize tissue alteration by using rapid high-pressure freezing (HPF) of hippocampal slice cultures. We used this approach to monitor fine-structural changes at hippocampal mossy fiber synapses associated with chemically induced long-term potentiation (LTP). Synaptic plasticity in LTP has been known to involve structural changes at synapses including reorganization of the actin cytoskeleton and de novo formation of spines. While LTP-induced formation and growth of postsynaptic spines have been reported, little is known about associated structural changes in presynaptic boutons. Mossy fiber synapses are assumed to exhibit presynaptic LTP expression and are easily identified by EM. In slice cultures from wildtype mice, we found that chemical LTP increased the length of the presynaptic membrane of mossy fiber boutons, associated with a de novo formation of small spines and an increase in the number of active zones. Of note, these changes were not observed in slice cultures from Munc13-1 knockout mutants exhibiting defective vesicle priming. These findings show that activation of hippocampal mossy fibers induces pre- and postsynaptic structural changes at mossy fiber synapses that can be monitored by EM. J. Comp. Neurol. 520:2340–2351, 2012. © 2012 Wiley Periodicals Inc.