Hippocampal mossy fiber sprouting and synapse formation after status epilepticus in rats: Visualization after retrograde transport of biocytin

摘要: In complex partial epilepsy and in animal models of epilepsy, hippocampal mossy fibers appear to develop recurrent collaterals, that invade the dentate molecular layer. Mossy fiber collaterals have been proposed subserve excitation by forming granule cell-granule cell synapses. This hypothesis was tested visualizing cells their after terminal uptake retrograde transport biocytin. Labeling studies were performed with transverse slices caudal rat formation prepared 2.6–l70.0 weeks pilocarpine-induced or kainic acid-induced status epilepticus. Light microscopy demonstrated progressive growth into layer; densest innervation observed from pilocarpine-treated rats had survived 10 longer Thin originated predominantly deep within hilar region, crossed body layer, formed an axonal plexus oriented parallel layer inner one-third When sprouting most robust, some at apex gyrus reached outer two-thirds The distribution density fiber-like Timm staining correlated biocytin labeling. viewed electron microscope, contained numerous boutons. instances, biocytin-labeled boutons engaged synaptic contact dendrites. Granule dendrites did not large spines (“thorny excrescences”) site synapse formation, they permanently damaged seizure activity. These results establish validity as a marker for support view epilepticus provokes novel excitatory circuit gyrus. Retrograde labeling showed projection often occupies considerably greater fraction dendritic region than previous suggested. © 1995 Wiley-Liss, Inc.