Immunohistochemical mapping of calcium-binding protein immunoreactivity in the rat central nervous system

A complete mapping of immunoreactive sites for vitamin D-dependent calcium-binding protein (CaBP) was performed on serial sections from the rat central nervous system. CaBP immunoreactivity was found in the perikarya, dendrites and axons of some neurons from the limbic system, from many neurosecretory nuclei, from most sensory nuclei and from the cerebral and cerebellar cortex. In contrast, no CaBP antigenic sites were detectable in the motoneurons of the spinal cord and in those of the cranial nerve nuclei, nor in the neurons from the cerebellar nuclei. A quantitative evaluation revealed a great variability in the number of CaBP-immunoreactive neurons among different areas of the central nervous system. Positive cells represented less than 1% of the neurons in the frontal cortex, whereas 74% of the Purkinje cells from the cerebellar cortex showed immunoreactive staining for CaBP. In addition, 45% of the ependymal cells of the telencephalic ventricles were positive. These data show that CaBP is widely distributed in neurons and ependymal cells from the rat central nervous system although it is more concentrated in some specific areas.