Organization of identified fiber tracts in the rat fimbria-fornix: an anterograde tracing and electron microscopic study.
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.
Adelmann
G
G
Institute of Anatomy, University of Freiburg, Germany.
Deller
T
T
Frotscher
M
M
D000818:Animals; D001253:Astrocytes / Q000648:ultrastructure; D002540:Cerebral Cortex / Q000737:chemistry / Q000648:ultrastructure*; D006624:Hippocampus / Q000737:chemistry / Q000648:ultrastructure*; D007267:Injections; D008854:Microscopy, Electron; D009412:Nerve Fibers / Q000648:ultrastructure*; D009836:Oligodendroglia / Q000648:ultrastructure; D010835:Phytohemagglutinins / Q000008:administration & dosage / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D013569:Synapses / Q000648:ultrastructure
D010835:Phytohemagglutinins