Fig. 7.

Rolipram, a phosphodiesterase that increases intracellular cyclic adenosine monophosphate (cAMP) in neurons or brief electrical stimulation accelerates axon outgrowth across the suture line of a transected and surgically repaired peripheral nerve in rats. (a) Rolipram administered locally to a surgically repaired common peroneal nerve or (b) 1 h continuous 20-Hz electrical stimulation proximal to the surgical repair site of a transected femoral nerve significantly increases the number of motoneurons that regenerate their axons. (c) Protein kinase A is activated by cAMP to promote transcription of proteins that include the neurotrophic factors that amplify the effects of cAMP in promoting gene transcription of growth associated genes such as tubulin and actin and, in turn, accelerate axon outgrowth (p < 0.05). BDNF = brain-derived neurotrophic factor; ATP = adenosine triphosphate; PKA = protein kinase A