Involvement of cAMP in neuronal survival and axonal regeneration.

In vitro, cAMP elevation alters neuronal responsiveness to diffusible growth factors and overcomes myelin-associated inhibitory molecules. Significant advances have been made recently in understanding the role of increases in cAMP in promoting axonal growth. Importantly, it has now been shown that cAMP elevation can promote axonal regeneration and functional recovery after central nervous system injury. Elevation of cAMP can be achieved via either direct application of cAMP analogs or an inhibitor of the enzyme phosphodiesterase that degrades cAMP in vivo. Current information points to a number of protein kinase A-mediated pathways (mitogen-activated protein kinase/extracellular signal-regulated kinase and phosphatidylinositol 3-kinase/akt pathway activation and Rho inactivation) underlying cAMP elevation-induced neuronal survival and axonal regeneration.