Expression of c-fos in hilar mossy cells of the dentate gyrus in vivo

Authors

  • Aine M. Duffy,

    1. Center for Dementia Research, The Nathan Kline Institute for Psychiatric Research, Orangeburg, New York
    Search for more papers by this author
  • Michael J. Schaner,

    1. Center for Dementia Research, The Nathan Kline Institute for Psychiatric Research, Orangeburg, New York
    Search for more papers by this author
  • Jeannie Chin,

    1. Department of Neuroscience, Thomas Jefferson University, Philadelphia, Pennsylvania
    Search for more papers by this author
  • Helen E. Scharfman

    Corresponding author
    1. Department of Child & Adolescent Psychiatry, Psychiatry, Physiology & Neuroscience, New York University Langone Medical Center, New York
    • Center for Dementia Research, The Nathan Kline Institute for Psychiatric Research, Orangeburg, New York
    Search for more papers by this author

Correspondence to: Helen E. Scharfman, The Nathan Kline Institute for Psychiatric Research Orangeburg, New York, NY 10962, USA. E-mail: hscharfman@nki.rfmh.org or helen.scharfman@nyumc.org

ABSTRACT

Granule cells (GCs) of the dentate gyrus (DG) are considered to be quiescent—they rarely fire action potentials. In contrast, the other glutamatergic cell type in the DG, hilar mossy cells (MCs) often have a high level of spontaneous activity based on recordings in hippocampal slices. MCs project to GCs, so activity in MCs could play an important role in activating GCs. Therefore, we investigated whether MCs were active under basal conditions in vivo, using the immediate early gene c-fos as a tool. We hypothesized that MCs would exhibit c-fos expression even if rats were examined randomly, under normal housing conditions. Therefore, adult male rats were perfused shortly after removal from their home cage and transfer to the laboratory. Remarkably, most c-fos immunoreactivity (ir) was in the hilus, especially temporal hippocampus. C-fos-ir hilar cells co-expressed GluR2/3, suggesting that they were MCs. C-fos-ir MCs were robust even when the animal was habituated to the investigator and laboratory where they were euthanized. However, c-fos-ir in dorsal MCs was reduced under these circumstances, suggesting that ventral and dorsal MCs are functionally distinct. Interestingly, there was an inverse relationship between MC and GC layer c-fos expression, with little c-fos expression in the GC layer in ventral sections where MC expression was strong, and the opposite in dorsal hippocampus. The results support the hypothesis that a subset of hilar MCs are spontaneously active in vivo and provide other DG neurons with tonic depolarizing input. © 2013 Wiley Periodicals, Inc.

Ancillary