Dibutyryl cyclic adenosine monophosphate stimulation of colcemid-inhibited axonal elongation

Adenosine 3',5'-monophosphate (cyclic AMP) and its dibutyryl derivative induce a variety of morphological changes, including those associated with in vitro axonal maturation. Established sensory ganglia treated with dibutyryl cyclic AMP show significant increases in average axonal length and number in comparison with controls; those treated with maintenance doses of Colcemid show no increases in either parameter; simultaneous treatment with both agents results in growth statistically similar to that produced by dibutyryl cyclic AMP alone. The data are consistent with our hypothesis that cyclic AMP promotes axonal elongation by stimulating microtubule assembly from a preexisting subunit pool.