The regulation of neurodevelopment by neuropeptides, trophic factors and electrical activity was studied with cell culture systems derived from the fetal mammalian central nervous system. The mechanism of the neuron survival-promoting effects of vasoactive intestinal peptide was shown to involve a neurotrophic factor releasing action which was mediated through nonneuronal cells. Two proteins (~40k and ~15 k) appear to be major substrates for VIP-induced phosphorylation in cortical astrocytes. Two cDNA clones have been isolated that when placed in an expression vector produced substances which enhanced tetanus toxin binding in hippocampal cultures, increase neuronal survival in ciliary ganglion cultures and enhance the survival of spinal cord neurons under TTX blockade. Two morphologically distinct cholinergic cell types from the basal forebrain were found to preferentially respond to NGF or phorbol esters. The decrease in neuronal survival produced by NMDA antagonists was shown to be restricted to a developmentally sensitive period. Neuronal cell death produced by electrical blockade with tetrodotoxin was prevented by NMDA or a calcium ionophore, A23187. These studies suggest the importance of the calcium regulation in determining which neurons survive during development.
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