The effects of exogenous nerve growth factor on foetal rat adrenal cells in culture.

Foetal rat adrenal cells, identified as chromaffin cells, maintained in culture in the presence of exogenous NGF, express a neuronal phenotype. Once this neuronal phenotype has been established bundles of outgrowing neurites commonly form links with adjacent reaggregates, and also develop synaptic contacts with the cell bodies of chromaffin cells in the adjacent reaggregates. Subsequent withdrawal of exogenous NGF from the culture medium did not result in the chromaffin cells losing their neuronal phenotype if this had been established before NGF was withdrawn. Tyrosine hydroxylase immunocytochemistry revealed that all neurites developed in culture were positive for the enzyme including those in cultures only transiently exposed to exogenous NGF. These results suggest that exogenous NGF may be essential only until the chromaffin cells develop neurites which make contact with appropriate target cells and that once these links, however immature, have been established, neurites are retained for many weeks in the absence of exogenous NGF.