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  • 1
    ISSN: 1432-0568
    Keywords: Phaseolus vulgaris-leucoagglutinin ; Hippocampus ; Septum ; Entorhinal cortex ; Limbic system ; Fimbria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The fimbria is a major route for afferent and efferent fibers of the hippocampal formation. However, little is known about the intrinsic organization of the fimbria-fornix complex. In this study, the anterograde tracer Phaseolus vulgaris-leucoagglutinin (PHAL) was used to analyze the ultrastructure and topography of identified fiber tracts within the fimbria-fornix. Septo-hippocampal fibers are loosely distributed throughout the fimbria-fornix. Commissural fibers cross the midline in the ventral hippocampal commissure and form a tight fiber bundle in the fimbria. Crossed entorhino-hippocampal fibers cross the midline in the ventral hippocampal commissure rostral to the commissural fiber bundle, and crossed entorhino-entorhinal fibers pass through the dorsal hippocampal commissure. This suggests a topographical organization of fiber tracts within the fimbria-fornix that reflects the laminar organization of the hippocampal target structure: fibers of the diffusely terminating septohippocampal projection are loosely distributed throughout the fimbria-fornix, while those projections that are known to terminate in specific laminae of the hippocampal formation (commissural projection, crossed entorhino-hippocampal projection) form fiber bundles within the fimbria and the ventral hippocampal commissure.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science, Ltd
    European journal of neuroscience 19 (2004), S. 0 
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Denervation of the dentate gyrus by entorhinal cortex lesion has been widely used to study the reorganization of neuronal circuits following central nervous system lesion. Expansion of the non-denervated inner molecular layer (commissural/associational zone) of the dentate gyrus and increased acetylcholinesterase-positive fibre density in the denervated outer molecular layer have commonly been regarded as markers for sprouting following entorhinal cortex lesion. However, because this lesion extensively denervates the outer molecular layer and causes tissue shrinkage, stereological analysis is required for an accurate evaluation of sprouting. To this end we have performed unilateral entorhinal cortex lesions in adult C57BL/6J mice and have assessed atrophy and sprouting in the dentate gyrus using modern unbiased stereological techniques. Results revealed the expected increases in commissural/associational zone width and density of acetylcholinesterase-positive fibres on single brain sections. Yet, stereological analysis failed to demonstrate concomitant increases in layer volume or total acetylcholinesterase-positive fibre length. Interestingly, calretinin-positive fibres did grow beyond the border of the commissural/associational zone into the denervated layer and were regarded as sprouting axons. Thus, our data suggest that in C57BL/6J mice shrinkage of the hippocampus rather than growth of fibres underlies the two morphological phenomena most often cited as evidence of regenerative sprouting following entorhinal cortex lesion. Moreover, our data suggest that regenerative axonal sprouting in the mouse dentate gyrus following entorhinal cortex lesion may be best assessed at the single-fibre level.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 286 (1996), S. 293-303 
    ISSN: 1432-0878
    Keywords: Key words: Phaseolus vulgaris leucoagglutinin ; Anterograde tracing ; Entorhinal cortex ; Crossed temporo-ammonic pathway ; Crossed temporo-dentate pathway ; Rat (Sprague Dawley)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. Neurons of the entorhinal cortex project to the hippocampus proper and dentate gyrus. This projection is called the ”perforant pathway” because it perforates the subiculum; current usage applies this term to all entorhino-hippocampal fibers. However, entorhinal fibers also reach Ammon’s horn via the alveus (”alvear pathway”), an alternative route first described by Cajal. The anterograde tracer Phaseolus vulgaris leucoagglutinin (PHAL) was used in order to analyze the contribution of this pathway to the temporo-ammonic projection. In the temporal portion of the rat hippocampus, most of the entorhinal fibers reach Ammon’s horn after perforating the subiculum (classical perforant pathway). At more septal levels, the number of entorhinal fibers that take the alvear pathway increases; in the septal portion of the hippocampal formation, most of the entorhinal fibers to hippocampal subfield CA1 reach this subfield via the alveus. These fibers make sharp right-angle turns in the alveus, perforate the pyramidal cell layer, and finally terminate in the stratum lacunosum-moleculare. The crossed temporo-ammonic fibers reach their termination area in the stratum lacunosum-moleculare of CA1 almost exclusively via the alveus. These data indicate that the alveus is a major route by which entorhinal fibers reach their targets in CA1.
    Type of Medium: Electronic Resource
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