The mossy cells of the fascia dentata: A comparative study of their fine structure and synaptic connections in rodents and primates
- 9 October 1991
- journal article
- research article
- Published by Wiley in Journal of Comparative Neurology
- Vol. 312 (1) , 145-163
- https://doi.org/10.1002/cne.903120111
Abstract
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. No major differences were found between mossy cells of rats and monkeys. The mossy cell dendrites originated from the two sides of an ovoid cell body and were mainly oriented parallel to the granule cell layer. In contrast to the rat, dendrites of mossy cells in the primate did not respect the granule cell layer and penetrated frequently into the molecular layer. The occurrence of excrescences on proximal dendrites was a characteristic feature of all mossy cells. These large spines were more complex in the primate than in the rat. In both rats and primates they formed numerous asymmetric synapses with large boutons of mossy fibers. Peripheral dendrites were covered with small, simple spines. Interestingly, these peripheral dendrites lacking excrescences also established asymmetric synapses with mossy fiber boutons as well as asymmetric and symmetric contacts with smaller terminals of unknown origin. These findings indicate that in both rats and primates the thorny excrescences are not the only target of the mossy terminals. While the proximal portions of the mossy cell dendrites appear to be exclusively contacted by the granule cells, a larger number of neuron types may converge on the distal dendrites. The axons of mossy cells, in both rats and primates, although incompletely stained with the present methods, were seen to ramify in‐the hilar region. Our results demonstrate that, despite minor species differences, the mossy cells of the fascia dentata represent a cell type that is preserved in phylogenetically distant species.Keywords
This publication has 30 references indexed in Scilit:
- Morphological variability is a characteristic feature of granule cells in the primate fascia dentata: A combined Golgi/electron microscope studyJournal of Comparative Neurology, 1990
- Fine structure of identified neurons in the primate hippocampus: A combined Golgi/EM study in the baboonJournal of Comparative Neurology, 1988
- Various types of non-pyramidal hippocampal neurons project to the septum and contralateral hippocampusBrain Research, 1986
- The cholinergic innervation of the rat fascia dentata: Identification of target structures on granule cells by combining choline acetyltransferase immunocytochemistry and Golgi impregnationJournal of Comparative Neurology, 1986
- The development, ultrastructure and synaptic connections of the mossy cells of the dentate gyrusJournal of Neurocytology, 1985
- Dendritic arbors and dendritic excrescences of abnormally positioned neurons in area CA3c of mice carrying the mutation “Hippocampal lamination defect”Journal of Comparative Neurology, 1985
- Mossy fibres form synapses with identified pyramidal basket cells in the CA3 region of the guinea-pig hippocampus: a combined Golgi-electron microscope studyJournal of Neurocytology, 1985
- Five types of basket cell in the hippocampal dentate gyrus: a combined Golgi and electron microscopic studyJournal of Neurocytology, 1983
- A golgi study of cell types in the hilar region of the hippocampus in the ratJournal of Comparative Neurology, 1978
- A new procedure for examining Golgi impregnated neurons by light and electron microscopyJournal of Neurocytology, 1977