Postnatal development of CA3 pyramidal neurons and their afferents in the Ammon's horn of rhesus monkeys

L. Séress, C. E. Ribak

Research output: Contribution to journalArticle

56 Citations (Scopus)

Abstract

Previous studies described the postnatal development of CA3 pyramidal neurons and their afferents in the rat. However, the postnatal development of the primate hippocampus was not previously studied. Thus, pyramidal neurons of the CA3 area of the monkey hippocampus were analyzed postnatally in the present study. At birth, a few thorny excrescences, the complex spines postsynaptic to messy fibers, were found on the proximal segments of both apical and basal dendrites, whereas distal dendrites displayed pedunculate spines. Thorny excrescences increased in number until the third month. A continuous increase in the number of spines per unit length along the distal dendrites was observed during the first 12 months. The ultrastructural features of somata and dendrites of pyramidal cells in newborn monkeys were similar to those of adults. The analysis of the afferents to the CA3 pyramidal neurons was limited to the development of messy fibers, the axons of granule cells, and myelinated axons in the alveus, stratum orlens, and stratum lacunosum-moleculare. At birth, most messy fiber terminals were densely packed with synaptic vesicles and formed mainly axospinous synapses with CA3 pyramidal cells. By 1 month of age, the number of mitochondria and embedded spines increased to mature amounts. In the first postnatal month, degenerating axons and axon terminals were frequently observed in the messy fiber bundles in stratum lucidum. The proportion of myelinated axons increased simultaneously in all three examined layers. At birth most axons were unmyelinated, whereas at 7 months of age the proportion of myelinated axons was similar to that found in adults. The present study indicates that most pyramidal neurons of the CA3 region in monkeys are in an advanced stage of development at the time of birth. Thus, messy fibers from granule cells in the dentate gyrus have established mature-looking synapses, and the thorny excrescences of pyramidal cells that are postsynaptic to messy fibers are also adult-like. Nevertheless, several of the adult features, such as the spine density of distal dendrites of pyramidal neurons and the myelination of afferent axons, develop during an extended period of time in the first year. The significance of this early anatomical maturation in a brain region involved in memory function is consistent with recent behavioral data that show a rapid postnatal maturation of limbic-dependent recognition memory in rhesus monkeys.

Original languageEnglish
Pages (from-to)217-231
Number of pages15
JournalHippocampus
Volume5
Issue number3
DOIs
Publication statusPublished - 1995

Fingerprint

Pyramidal Cells
Macaca mulatta
Hippocampus
Axons
Dendrites
Spine
Parturition
Haplorhini
Synapses
Synaptic Vesicles
Dentate Gyrus
Presynaptic Terminals
Carisoprodol
Primates
Mitochondria
Brain

Keywords

  • Golgi-electron microscopy
  • Hippocampus
  • Primate
  • Timm staining

ASJC Scopus subject areas

  • Neuroscience(all)

Cite this

Postnatal development of CA3 pyramidal neurons and their afferents in the Ammon's horn of rhesus monkeys. / Séress, L.; Ribak, C. E.

In: Hippocampus, Vol. 5, No. 3, 1995, p. 217-231.

Research output: Contribution to journalArticle

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