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| Thomas Freiman |
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Department of Neurosurgery, Neurocentre, University Clinics, Breisacher Strasse 64, D-79106 Freiburg im Breisgau
e-mail: freiman@nz.ukl.uni-freiburg.de |
Poster Presentation: |
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| IN VITRO TRACING OF HUMAN HIPPOCAMPI FOR THE ANALYSIS OF AXONAL CONNECTIVITY IN TEMPORAL LOBE EPILEPSY – A TECHNICAL NOTE. |
| 1Freiman T.M., 1,2Gimbel K., 1Zentner J., 2Frotscher M., 3Deller T. | |
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1Department of Neurosurgery, 2Institute of Anatomy, Albert-Ludwigs-University, D-79106 Freiburg, 3Institute of Clinical Neuroanatomy, Johann Wolfgang Goethe-University, D-60590 Frankfurt, Germany |
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| Objective: Temporal lobe epilepsy (TLE) is frequently associated with hippocampal sclerosis. These hippocampi show a significant neuron loss, astrogliosis and remodeling of axonal pathways. It is believed that changes in axonal connectivity lead to abnormal hippocampal circuitry that contributes to seizure genesis. Although changes in hippocampal connectivity have been analyzed extensively in animal models of TLE, almost no data are available on the connectivity of the human hippocampus. Therefore, an extracellular tracing method was developed that makes it possible to analyze the local connectivity of the human hippocampus in vitro.
Methods: Hippocampal specimen were obtained from hippocampi of patients treated for pharmaceutically intractable TLE (n=7). Hippocampal slices obtained from patients with intracerebral tumors served as controls (n=3). Slices were kept in a slice chamber and the anterograde tracer neurobiotin was iontophoretically applied into the granule cell layer of the dentate gyrus. After several hours, the slices were fixed and the tracer was visualized. Moreover, anterograde tracing was combined with immunocytochemistry for several neuronal markers.
Results: Neurobiotinin-labeled granule cells were identified and the axonal arbor of single granule cells was reconstructed partially. Numerous mossy fibers were found in the inner moleular layer of the sclerotic dentate gyrus. These axons impinge on granule cells as well as calretinin-immunoreactive interneurons. Electron microscopy revealed mossy fiber synapses on spiny neurons, presumably granule cells.
Conclusion: In vitro anterograde tracing of human hippocampi can be used to analyze hippocampal connectivity in TLE. Our data demonstrate that sprouting mossy fibers target granule cells as well as some interneurons in the sclerotic human hippocampus.
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