Increasing cAMP overcomes the inhibition of SGN neurite growth by astrocytes or oligodendrocytes. A. SGN neurite growth from SG explants plated on SCs, ACs, or OLs. Cultures were immunostained with anti-NF200 (red) and either anti-S100, anti-GFAP, or RIP (green) antibodies as indicated. Nuclei were labeled with Hoechst (blue). Neurite outgrowth on SCs was robust, radially oriented, and fasciculated. B. Mean B number of neurites/explant on different cell backgrounds. There was significantly reduced neurite outgrowth on ACs or OLs (p<0.01). Application of cpt-cAMP or forskolin significantly increased the number of neurites on OLs (p<0.01). The increase in neurite outgrowth on ACs by cpt-cAMP (1 mM) or forskolin (5 μM) was not statistically significant different from untreated cultures (p=0.30).