title: Comparison of commissural sprouting in the mouse and rat fascia dentata after entorhinal cortex lesion.
abstract: Reactive axonal sprouting occurs in the fascia dentata after entorhinal cortex lesion. This sprouting process has been described extensively in the rat, and plasticity-associated molecules have been identified that might be involved in its regulation. To demonstrate causal relationships between these candidate molecules and the axonal reorganization process, it is reasonable to analyze knockout and transgenic animals after entorhinal cortex lesion, and because gene knockouts are primarily generated in mice, it is necessary to characterize the sprouting response after entorhinal cortex lesion in this species. In the present study, Phaseolus vulgaris-leucoagglutinin (PHAL) tracing was used to analyze the commissural projection to the inner molecular layer in mice with longstanding entorhinal lesions. Because the commissural projection to the fascia dentata is neurochemically heterogeneous, PHAL tracing was combined with immunocytochemistry for calretinin, a marker for commissural/associational mossy cell axons. Using both techniques singly as well as in combination (double-immunofluorescence) at the light or electron microscopic level, it could be shown that in response to entorhinal lesion mossy cell axons leave the main commissural fiber plexus, invade the denervated middle molecular layer, and form asymmetric synapses within the denervated zone. Thus, the commissural sprouting response in mice has a considerable translaminar component. This is in contrast to the layer-specific commissural sprouting observed in rats, in which the overwhelming majority of mossy cell axons remain within their home territory. These data demonstrate an important species difference in the commissural/associational sprouting response between rats and mice that needs to be taken into account in future studies.
authors.affiliation: Institute of Clinical Neuroanatomy, J. W. Goethe University, Frankfurt/Main, Germany.
authors.forename: Domenico
authors.initials: D
authors.lastname: Del Turco
authors.forename: Alisa G
authors.initials: AG
authors.lastname: Woods
authors.forename: Carl
authors.initials: C
authors.lastname: Gebhardt
authors.forename: Amie L
authors.initials: AL
authors.lastname: Phinney
authors.forename: Mathias
authors.initials: M
authors.lastname: Jucker
authors.forename: Michael
authors.initials: M
authors.lastname: Frotscher
authors.forename: Thomas
authors.initials: T
authors.lastname: Deller
mesh_terms: D000818:Animals; D064032:Calbindin 2; D003714:Denervation; D018891:Dentate Gyrus / Q000254:growth & development* / Q000502:physiology* / Q000648:ultrastructure; D018728:Entorhinal Cortex / Q000166:cytology / Q000293:injuries / Q000502:physiology*; D020439:Growth Cones / Q000502:physiology* / Q000648:ultrastructure; D007150:Immunohistochemistry; D051379:Mice; D008810:Mice, Inbred C57BL; D008854:Microscopy, Electron; D019599:Mossy Fibers, Hippocampal / Q000502:physiology* / Q000648:ultrastructure; D009434:Neural Pathways / Q000254:growth & development* / Q000502:physiology*; D009473:Neuronal Plasticity / Q000502:physiology*; D010835:Phytohemagglutinins; D017729:Presynaptic Terminals / Q000502:physiology / Q000648:ultrastructure; D051381:Rats; D017207:Rats, Sprague-Dawley; D064030:S100 Calcium Binding Protein G / Q000378:metabolism; D013045:Species Specificity
chemical_list: C576511:Calb2 protein, mouse; C576512:Calb2 protein, rat; D064032:Calbindin 2; D010835:Phytohemagglutinins; D064030:S100 Calcium Binding Protein G; C100156:leukoagglutinins, plants