Distribution of 1,25-dihydroxyvitamin D3 receptor immunoreactivity in the limbic system of the rat

We used immunocytochemistry to obtain a complete cellular and subcellular m apping of the 1,25-dihydroxyvitamin D3 receptor protein (VDR) in the rat li mbic system. We observed specific VDR immunostaining in the nucleus as well as in the perinuclear cytoplasm of neuronal cells. The limbic system consi sts of a variety of neuronal structures, and is known to have influence on memory, behavior, emotions and reproduction. In the hippocampal formation, we found strong nuclear staining as well as less distinguished cytoplasmic VDR staining in CA1, CA3 and CA4. The CA2 area showed a unique cytoplasmic predominance of VDR. The amygdala was found to exhibit specific patterns of VDR distribution in the various regions of the nucleus. We observed distin ct differences of VDR localization within the limbic preoptic areas of the hypothalamus. Further parts of the brain we analyzed included the mammillar y bodies, the indusium griseum and the cingulate cortex. The subcellular di stribution of VDR in regions of the limbic system suggests a specific funct ional role of the receptor protein and indicates a role for calcitriol as a neuroactive steroid.