The mossy cells of the fascia dentata: A comparative study of their fine structure and synaptic connections in rodents and primates

In this study the fine structure and synaptic connections of mossy cells in the rat and monkey fascia dentata were analyzed. In order to study commissural connections of identified mossy cells in the rat, hilar neurons were retrogradely labeled by horseradish peroxidase (HRP) or Fast Blue (FB) injections into the contralateral hippocampus. Vibratome sections containing retrogradely HRP‐labeled hilar neurons were Golgi‐impregnated and gold‐toned. Hilar commissural neurons identified by contralateral FB injection were intracellularly labeled with Lucifer Yellow (LY). Lucifer Yellow staining was made electron‐dense by photoconversion thereby allowing for an electron microscopic analysis of the retrogradely labeled and intracellularly stained neurons. With these two different approaches, we succeeded in identifying rat mossy cells projecting to the contralateral hippocampus. Mossy cells in the fascia dentata of primates (Papio anubis, Macaca mulatto, Saimiri sciureus) were, like mossy cells of rats, either Golgi‐impregnated and gold‐toned or intracellularly injected with LY.

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