Purpose: The mechanism underlying forced limb-use -induced structural plasticity remains to be studied. We examined whether the cyclic adenosine monophosphate (cAMP)-mediated signal transduction pathway was involved in brain plasticity and promoted behavioral recovery induced by forced limb-use after stroke.
Methods: Adult rats were divided into a sham group, an ischemia group, an ischemia group with forced limb-use, and an ischemia group with forced limb-use and infusion of N-[2-(p-bromocinnamylamino)ethyl]-5-isoquinoline-sulfonamide (H89). Forced limb-use began on post-stroke day 7. Biotinylated dextran amine (BDA) was injected into the sensorimotor cortex on post-stroke day 14. Behavioral recovery was evaluated on post-stroke days 29 to 32, and the levels of cAMP, PKA C-α, phosphorylated CREB (pCREB), synaptophysin, PSD-95, BDA, and BrdU/NeuN were measured.
Results: The number of midline-crossing axons and the expression levels of synaptophysin and PSD-95 were increased after forced limb-use. Forced limb-use enhanced the survival of the newborn neurons and increased the levels of cAMP, PKA C-α and pCREB. These were significantly suppressed by H89. Behavioral performance improved with forced limb-use and was reversed with H89.
Conclusions: Enhanced structural plasticity and the behavioral recovery promoted by post-stroke forced limb-use are suggested to be mediated through the cAMP/PKA/CREB signal transduction pathway.
Keywords: Axonal growth; cAMP; forced limb-use; neurogenesis; stroke.