S‐100β and insulin‐like growth factor‐II differentially regulate growth of developing serotonin and dopamine neurons in vitro

Abstract

To study the phenotypic specificity of S‐100β and insulin‐like growth factor II (IGF‐II) for developing monoamine neurons, serotonin (5‐HT) neurons from the embryonic day 14 (E14) rostral raphe or dopamine (TH) neurons from the substantia nigra/ventral tegmental area were cultured for 3 days in vitro (3 DIV) in the presence of these factors. Neuronotrophic effects were analyzed by computer‐assisted morphometry of 5‐HT and TH‐immunoreactive neurons. S‐100β significantly increased several parameters of neurite outgrowth by 5‐HT neurons but inhibited the spatial extent (field area) of TH neurites. IGF‐II promoted growth of cell bodies of both phenotypes, but only stimulated neurite outgrowth by TH neurons. S‐100β and IGF‐II differentially affected the number of GFAP immunoreactive cells from raphe and substantia nigra, but these effects did not correlate with the specificity of neuronotrophic effects. S‐100β and IGF‐II immunoreactivities were expressed in glial cultures derived from the same brain regions, raising the possibility that these factors have autocrine effects on glia as well as paracrine actions on neurons. The results of this study suggest that specificity of neuronotrophic factors for particular embryonic neurons may be correlated with their neurotransmitter phenotype. © Wiley‐Liss, Inc.