Distribution of a specific calcium-binding protein of the S100 protein family, S100A6 (calcyclin), in subpopulations of neurons and glial cells of the adult rat nervous system

S100A6 (calcyclin) is a member of the large S100 Ca2+-binding protein famil y, considered to activate several processes along the calcium signal transd uction pathway including the regulation of cell growth, proliferation, secr etion, and exocytosis. In the present study, the distribution of S100A6 in the rat nervous system was examined by immunohistochemistry with a goat ant iserum against recombinant human S100A6, which recognizes the rat S100A6 ho mologue. The main S100A6-immunoreactive elements were I) neuronal somata an d dendrites in some specific regions of the limbic system (e.g., the basola teral amygdaloid nucleus, ventral tip of the CA1-subicular border region, e ntorhinal cortex, and parasubiculum), most of which were identified as a su bpopulation of pyramidal cells; 2) olfactory receptor cells and olfactory n erve fibers and terminals in the olfactory bulb; 3) some tracts of the hind brain and spinal cord (e.g., the spinal trigeminal tract, solitary tract, d orsal root fibers, and the tract of Lissauer) and their terminals (e.g., th e principal sensory trigeminal nucleus, spinal trigeminal nucleus, nucleus of the solitary tract, marginal zone, substantia gelatinosa, and proper sen sory nucleus of the dorsal horn), as well as some sensory neurons of their origins in the dorsal root and trigeminal ganglia; 4) a subpopulation of as trocytes in the white matter (e.g., the corpus callosum, cingulum, external capsule, internal capsule, and fimbria of the hippocampus) and around the ventricles; 5) some ependymal cells, especially around the central canal; a nd 6) Schwann cells. These results will improve our understanding of the di verse function of Ca2+-binding proteins in the CNS. (C) 1999 Wiley-Liss, In c.