Transneuronal effects of entorhinal lesions in the early postnatal period on synaptogenesis in the hippocampus of the rat

M. Frotscher, J. Hámori, J. Wenzel

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Abstract

The granule cell axons of the dentate gyrus (mossy fibers, MF) terminate with large, characteristic boutons on neurons of the regio inferior of the hippocampus. To study transneuronal effects on mossy fiber synaptogenesis, the entorhinal cortex, which is the source of the main afferent to the granule cells, was removed in 3-day old rats. After a postoperative survival time of 27 days, the animals were killed and the brain prepared for electron microscopy. No clear postlesional changes were observed in the inner structure of the presynaptic mossy fiber terminals. The mean size of MF boutons was roughly the same in the experimental animals as compared to normal, unoperated rats of the same age (4.19 μm2, SD 1.9; and 4.29 μm2, SD 2.2, respectively). On the postsynaptic side, however, some remarkable changes were found. In the operated animals, the number and total area of dendritic spines in synaptic contact with MF has significantly decreased in comparison with the controls. Also the size of a single spine in the operated animals was only 64 % of that in the normal. These changes were accompanied by a decrease in MF total perimeter and MF-dendritic contact length in the experimental animals. The length of the MF specialized synaptic contact was found to be correlated with the number and size of dendritic spines. Thus accordingly, though the length of the MF specialized contact with the dendritic shaft did not change, the absolute length of MF specialized contact with postsynaptic spines was decreased in the lesioned animals due to the numerical and size reduction of the spines. This suggests that normally functioning entorhinal afferents to the granule cells are necessary for the normal development of dendritic spines in contact with hippocampal mossy fibers.

Original languageEnglish
Pages (from-to)549-560
Number of pages12
JournalExperimental Brain Research
Volume30
Issue number4
DOIs
Publication statusPublished - Dec 1977

Fingerprint

Hippocampus
Dendritic Spines
Spine
Hippocampal Mossy Fibers
Hippocampal CA3 Region
Entorhinal Cortex
Dentate Gyrus
Axons
Electron Microscopy
Neurons
Brain

Keywords

  • Entorhinal lesion
  • Hippocampus
  • Synaptogenesis
  • Transneuronal effects

ASJC Scopus subject areas

  • Neuroscience(all)

Cite this

Transneuronal effects of entorhinal lesions in the early postnatal period on synaptogenesis in the hippocampus of the rat. / Frotscher, M.; Hámori, J.; Wenzel, J.

In: Experimental Brain Research, Vol. 30, No. 4, 12.1977, p. 549-560.

Research output: Contribution to journalArticle

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