Cyclic GMP in a Neuroblastoma Clone: Possible Involvement in Morphological Differentiation Induced by Dibutyryl Cyclic Amp

DBcAMP induces morphological differentiation of mouse neuroblastoma cells grown in culture. DBcGMP or 8‐Br cyclic GMP when added alone also induces a discrete morphological differentiation. When analogues of cyclic GMP were added together with dBcAMP, neurite outgrowth was strikingly enhanced as compared to the effect of dBcAMP alone. Intracellular concentrations of cyclic GMP were increased during dBcAMP treatment and cyclic AMP levels were increased during 8‐Br cyclic GMP treatment. Both treatments produced an increased protein kinase activity, supporting the possibility that not only cyclic AMP but also cyclic GMP may be involved in the differentiation process.