Article
Pathological change of the morphology and synaptic spine densities of dendrites of granule cells in patients suffering from temporal lobe epilepsy
Pathologische Veränderung der Dichte von synaptischen Spines an Dendriten von Körnerzellen im Hippocampus von Patienten mit Temporallappen-Epilepsie
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Published: | April 23, 2004 |
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Outline
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Objective
Temporal lobe epilepsy (TLE) is frequently associated with a sclerosis of the hippocampus, also known as Ammon’s horn sclerosis (AHS). These hippocampi show a significant neuron loss with astrogliosis and an enlargement of the granule cell layer (GCL dispersion). The GCL is a cell layer which is surprisingly not affected by the neuron loss. In a former paper we have already demonstrated that these granule cells of AHS patients display a dramatic change of their axons (mossy fibres), which grow back to their original cell layer. We examined the morphology and the density of dendritic synaptic input (dendritic spines) of granule cells.
Methods
Hippocampal specimens were obtained from hippocampi of patients treated for pharmaceutically intractable TLE (n=12) and with temporal tumours, who served as controls (n=3). The GCL dispersion and the back-grown mossy fibres of the two groups were compared with Silver-Impregnations. The granule cells were reconstructed and the morphology and spine density were evaluated by an optical analysis system (Neurolucida).
Results
Dendrites of granule cells of AHS patients display a swelling and a spine loss of their apical dendrites. This spine loss correlates with the extent of GCL dispersion. In addition to the spine loss, these granule cells develop newly-formed basal dendrites with a compensatory increased spine density.
Conclusions
Spines on apical dendrites of granule cells reflect the normal input. As the mossy fibre system grows back to the GCL, a dramatic change of synaptic input occurs and leads to changes of the spine density. The basal dendrites lose spines and the new basal dendrites probably form new synaptic contacts because they are closer to the back-grown mossy fibres.