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Synaptic extensions from the mossy fibers of the fascia dentata

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Summary

In the hilar region of the rat hippocampus, filamentous extensions have been observed to originate from the en passant synaptic expansions on the so-called mossy fibers, which are the axons of the dentate granule cells. These extensions range in length from about 1 μm to 30 μm, are often branched, and appear to contact the processes of various cell types in the hilar region. In 28-day-old rats, there are between 4 and 9 such extensions from most mossy fiber expansions, and the total length of the extensions from any one expansion is on the order of 75 μm. Analysis of serial electron micrographs through normal and Golgi-impregnated mossy fibers has confirmed that these extensions are, indeed, presynaptic processes. Each contains one or more vesicle-rich foci along its length, and is associated with asymmetric membrane specializations. At these sites, the extensions are in synaptic contact with dendrites and dendritic spines of, as yet, unknown origin. A quantitative analysis of these extensions in Golgi material from rats at different ages indicates that they reach their greatest length around 14 days and then decline to adult values by 28 days.

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Authors and Affiliations

  1. Department of Anatomy and Neurobiology, Washington University School of Medicine, 660 South Euclid Avenue, 63110, St. Louis, Missouri, USA

    David G. Amaral

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  1. David G. Amaral
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This work was supported in part by grant NS-10943 and was carried out while the author was in receipt of a U.S. Public Health Service post-doctoral fellowship (F32 NSO 5765-02)

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Amaral, D.G. Synaptic extensions from the mossy fibers of the fascia dentata. Anat Embryol 155, 241–251 (1979). https://doi.org/10.1007/BF00317638

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  • DOI: https://doi.org/10.1007/BF00317638

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