Distribution of GABAergic cells and fibers in the hippocampal formation of the macaque monkey: An immunohistochemical and in situ hybridization study

Ana L. Jongen-Rêlo, Asla Pitkänen, David G Amaral

Research output: Contribution to journalArticle

20 Scopus citations

Abstract

The γ-aminobutyric acid (GABAergic) system of the hippocampal formation of Macaca fascicularis monkeys was studied immunohistochemically with a monoclonal antibody to GABA and with nonisotopic in situ hybridization with cRNA probes for glutamic acid decarboxylase 65 (GAD65) and GAD67. The highest densities of labeled cells were observed in the presubiculum, parasubiculum, entorhinal cortex, and subiculum, whereas the CA3 field and the dentate gyrus had the lowest densities of positive neurons. Within the dentate gyrus, most of the GABAergic neurons were located in the polymorphic layer and in the deep portion of the granule cell layer. GABAergic terminals were densest in the outer two-thirds of the molecular layer. GABAergic neurons were seen throughout all layers of the hippocampus. Terminal labeling was highest in the stratum lacunosum-moleculare. A higher terminal labeling was observed in the subiculum than in CA1 and was particularly prominent in layer II of the presubiculum. A bundle of GABAergic fibers was visible deep to the cell layers of the presubiculum and subiculum. This bundle could be followed into the angular bundle ipsilaterally and was continuous with stained fibers in the dorsal hippocampal commissure. This pattern of labeling is reminiscent of the presubicular projections to the contralateral entorhinal cortex. GABAergic cells were observed in all layers of the entorhinal cortex although the density was higher in layers II and III than in layers V and VI. The in situ hybridization preparations largely confirmed the distribution of GABAergic neurons in all fields of the hippocampal formation.

Original languageEnglish (US)
Pages (from-to)237-271
Number of pages35
JournalJournal of Comparative Neurology
Volume408
Issue number2
DOIs
StatePublished - May 31 1999

Keywords

  • Dentate gyrus
  • Entorhinal cortex
  • Glutamic acid decarboxylase
  • Parasubiculum
  • Presubiculum
  • Subiculum

ASJC Scopus subject areas

  • Neuroscience(all)

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