Number and regional distribution of GAD65 mRNA-expressing interneurons in the rat hippocampal formation

B. Czéh, Hajnalka Ábrahám, Siroun Tahtakran, Carolyn R. Houser, L. Seress

Research output: Contribution to journalArticle

6 Citations (Scopus)


In rodent models for neuropsychiatric disorders reduced number of hippocampal interneurons have been reported, but the total number of GABAergic neurons in the normal rat hippocampus is yet unknown. We used in situ hybridization method to label the 65 isoform of glutamic acid decarboxylase (GAD65) and counted the number of GAD65 mRNA-expressing neurons along the entire septo-temporal axis of the hippocampus. We found that 2/3 of the interneurons were in Ammon's horn (61,590) and 1/3 in the dentate gyrus (28,000). We observed the following numbers in Ammon's horn: CA3 area 33,400, CA2 area 4,190, CA1 area 24,000 and in the dentate gyrus: 6,000 in the molecular and 9,000 in the granule cell layers and 13,000 in the hilus. GAD65 mRNA-expressing neurons were significantly more numerous in dorsal than in ventral hippocampus. The ratio between interneurons and principal cells was lowest in the granule cell layer (0.9%) and highest in hilus (21%). In Ammon's horn this ratio was constant being 13% in CA3 and 8% in CA1-2 areas. In the entire hippocampal formation, the interneuron/principal cell ratio was 6%, with a significant difference between Ammon's horn (9.5%) and the dentate gyrus (2.8%) including the hilus. Such low ratios could suggest that even a limited loss of GABAergic neurons in the hippocampus may have a considerable functional impact.

Original languageEnglish
Pages (from-to)395-413
Number of pages19
JournalActa biologica Hungarica
Issue number4
Publication statusPublished - Dec 1 2013


  • Cell number
  • GABA
  • Glutamic acid decarboxylase
  • Hippocampus
  • Stereology

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)
  • Environmental Science(all)
  • Neurology

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