IMMUNOHISTOCHEMICAL LOCALIZATION OF S100 PROTEINS IN DORSAL-ROOT, SYMPATHETIC AND ENTERIC GANGLIA OF SEVERAL MAMMALIAN-SPECIES, INCLUDING MAN

The occurrence of S100 proteins in neurons of the mammalian peripheral nervous system is still controversial. This study was designed to inv estigate this topic in dorsal root ganglia (DRG) and the enteric nervo us system (ENS) of several mammalian species (horse, buffalo, cow, she ep, pig, dog, rabbit and rat), as well as in DRG, paravertebral sympat hetic ganglia (SG) and ENS of the adult man. Rat embryos of E17 and E1 9 were also examined. The material was fixed in Bouin's fixative, para ffin-embedded and processed for immunohistochemistry, combined with im age analysis, using a panel of mono and polyclonal antibodies against S100 alpha, S100 beta or S100 alpha+beta (referred to here as S100) pr oteins. In all species examined, strong S100 protein immunoreactivity (IR) was found in satellite glial cells and Schwann cells, which also showed S100 alpha and S100 beta IR in humans. Furthermore, faint S100 protein IR was observed in a subpopulation of DRG intermediate- and la rge-sized sensory neurons in humans, buffalo, sheep, and pig. The rat was the only species showing clear S100 and S100 beta in neurons, labe lling in about 30-35% in adults (small, intermediate and large in size ), and about 88% at E17 and 42% at E19, respectively. Weak S100 alpha. protein IR was observed in most of human SG neuron. In ENS, S100 prot ein IR was restricted to enteric glial and Schwann cells, with the exc eption of cow and goat in which a subset of neurons in both the myente ric and submucous plexuses displayed strong S100 protein IR. Neuronal S100 alpha IR and glial S100 beta IR was found in the human ENS. The p resent results demonstrate intra- and inter-specific differences in th e expression of S100 proteins by neurons of the peripheral nervous sys tem among mammalian species. Furthermore, they also suggest that neuro nal S100 protein, at least in humans, consists of both S100a and S100 beta.