Cortical Axon Regeneration Compound Screen. 960 compounds (MicroSource Gen-Plus compound library) were screened in duplicate to identify compounds which promote cortical axon regeneration in the presence of CSPG. A, Photomicrographs of control wells immunostained for βIII-tubulin. Cortical cultures were scraped at 21 DIV and regenerated for 5 days under the indicated conditions. B, Quantification of axon regeneration for control conditions. CSPG inhibits cortical axon regeneration and this inhibition is attenuated by Y27632 (positive control). C, Preliminary hits. D, Concentration-responses for preliminary hits. Verapamil (10 μM) and bromopride (100 μM) significantly promote axon regeneration in the presence of CSPG. E, Photomicrographs demonstrating enhanced regeneration in the presence of verapamil (10 μM) and bromopride (100 μM). Data are mean ± S.E. n = 3-42. Scale bars, 100 μm. *, p < 0.05; **, p < 0.01 vs. CSPG control, Student’s two-tailed t-test (B) or one-way ANOVA, post hoc Dunnett (D). CSPG, chondroitin sulfate proteoglycan.