EARLY NEUROBLASTS ARE PLURIPOTENTIAL - COLOCALIZATION OF NEUROTRANSMITTERS AND NEUROPEPTIDES

This study was undertaken in order to establish the presence of plurip otential neuroblasts in the developing chick CNS. This has been sugges ted by our previous observations that expression of emerging neuronal phenotypes in the chick embryo CNS is affected by exposure to neurotro phic substances (i.e., GHRH, SRIF, NGF, EGF, muscle-derived factors) o r neurotoxins such as ethanol. We have proposed that one mechanism whe reby these substances elicit their effects is by shifting phenotypic e xpression in populations of pluripotential neuroblasts. In order to es tablish the presence of significant populations of pluripotential neur oblasts, cultures obtained from 3-day-old whole chick embryos (E3WE) w ere double-stained with antibodies to markers specific for four neuron al phenotypes in various permutations. Cultures at 6 DIV were tested f or the presence of tyrosine hydroxylase (TH), choline acetyltransferas e (ChAT), gamma-aminobutyric acid (GABA), and somatostatin (SRIF) alon e, and in various combinations. We observed a colocalization of all ph enotypic markers within neuronal perikarya and processes in more than fifty percent of neuronal cells in these cultures. These data suggest that developing neuroblasts at this stage of embryogenesis possess the machinery necessary to adopt multiple neuronal phenotypes. The coloca lization of neurotransmitter proteins in early neuroblasts (60 hr of e mbryogenesis) supports the recent concept that these substances themse lves may influence phenotypic expression and also supports our idea th at microenvironmental factors (i.e., ethanol, growth factors) provide signals which affect emerging phenotypes. (C) 1995 Wiley-Liss, Inc.