We investigated the distribution and colocalization pattern of the two corticosteroid receptors
mineralocorticoid receptor (MR) and glucocorticoid receptor (GR)
in the hippocampus and hypothalamus
the main target regions of corticosterone in the rat brain
using double immunofluorescence histochemistry in conjunction with specific polyclonal antibodies against MR and GR. In the hippocampus
MR- and GR-immunoreactivity (ir) were colocalized in CA1 and CA2 pyramidal neurons and granule cells of the dentate gyrus
while only MR-ir was seen in the CA3 pyramidal neurons. Colocalization of MR- and GR-ir was also observed in the parvocellular region
but not in the magnocellular region of the paraventricular nucleus (PVN). Subcellular distribution of MR-ir was more cytoplasmic in comparison with that of GR-ir
while the ratio of cytoplasmic to nuclear distribution of these receptors was different among the regions. After adrenalectomy (ADX)
the distribution pattern of both receptors was changed to cytoplasmic
although the degree of the change of distribution was different among each region. Replacement of corticosterone after ADX recovered the distribution pattern to that of the sham-operated animals. These results suggest that the balance of MR and GR in the cell underlies the potential regulation of corticosteroid through the hippocampus and hypothalamus. c 2004 Elsevier Ireland Ltd and the Japan Neuroscience Society. All rights reserved.
