MORPHOLOGICAL STUDY ON THE SURVIVAL AND AXONAL GROWTH OF TELENCEPHALIC AND BRAINSTEM NEURONS BY S-100beta.

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The homozygote of a mouse strain with genetic polydactyly (Polydactyly Nagoya ; Pdn) shows significant decrease of S-100beta in the brain. in order to clarify the effects of the retarded production of S-100beta on the development of monoaminergic neuron systems and glia cells, immunohistochemical studies of tyrosine hydroxylase (TH), serotonin, S-100beta and glial fibrillary acidic protein (GFAP) was performed. In all types of mice, S-100beta positive cells and serotonergic fibers were widely distributed throughout the brains and serotonergic cell bodies were located in the brainstem. However, the hippocampus and caudo-dorsal cortex of Pdn/Pdn mouse were markedly reduced in S-100beta positive cells and in serotonergic fibers. Furthermore, abnormal distribution of GFAP positive cells and fibers were observed in the cortex and hippocampus of Pdn/Pdn brain. No differences were seen in the distribution of TH neurons and fibers distribution. The present result suggests that the developmenta … More l defect of serotonergic fibers in the Pdn mutant mouse is correlate to the deficiency of S-100beta in the astrocyte of this mutant. To further clarify the effects of target tissues from different type brains on the development od serotonergic neurons, raphe neurons from Pdn/Pdn or+/+ newborn mice were co-cultured with hippocampus or cortex of +/+ or Pdn/Pdn newborn mice. The growth of serotonergic neurons in the mesencephalic raphe tissue dissociated cultures was estimated by measuring the specific uptake of [^3H] 5HT.The development of both genotypes (Pdn/Pdn and +/+) of serotonergic neurons was enhanced by co-cultures with target tissue (hippocampus and cortex) of +/+ brain. This effect was not observed in the co-cultures with Pdn/Pdn brain as a source of target tissue. The present results support the idea that the developmental defect of serotonergic fibers in the Pdn mutant mouse is correlate to the deficiency of S-100beta in the astrocyte of this mutant, and suggest that S-100beta is a serotonergic growth factor. Less