METABOLIC REQUIREMENTS FOR DIFFERENTIATION OF EMBRYONIC SYMPATHETIC-GANGLIA CULTURED IN THE ABSENCE OF EXOGENOUS NERVE GROWTH-FACTOR

The embryonic mouse superior cervical ganglion (SCG) in culture was employed to define the role of ongoing metabolic processes in morphological and biochemical development. The 14 gestational day SCG does not require added nerve growth factor (NGP) for differentiation in vitro. Its use allows study of intraganglionic regulation of neuronal growth in the absence of complicating, exogenous growth factors. Ganglia were cultured without added NGF, in medium containing various metabolic inhibitors; neurite elaboration and development of tyrosine hydroxylase (T-OH) activity, a biochemical marker of adrenergic maturation, were evaluated. Neurite elaboration proceeded normally with inhibition of RNA synthesis by actinomycin D or of protein synthesis by cycloheximide or puromycin. Inhibition of RNA or protein synthesis prevented normal development of T-OH activity. Neurites and T-OH developed normally in the presence of DNA synthesis inhibition by cytosine arabinoside, which markedly reduced the nonneuronal cell population. Neurite elaboration and the ontogenetic increase in T-OH activity apparently are regulated differently in ganglia cultured in the absence of exogenous NGF. The initial outgrowth of neurites and increase in T-OH activity may occur independent of peripherally migrating support cells in this embryonic ganglion.