Immunophilins are a class of proteins that are known for their roles in mediating the immunosuppressive actions of FK506, cyclosporin A (CsA), and rapamycin. FK506 and rapamycin bind to the FK506 binding proteins (FKBPs), while CsA binds to the family of cyclophilins. Reports have shown that immunophilins are expressed in the brain and spinal cord and are 10-100 fold higher in CNS tissue than immune tissue. Furthermore, immunophilin expression is increased following nerve injury, suggesting potential therapeutic utility for immunophilin ligands. We have shown that treatment with FK506, FK520, CsA, or rapamycin for 72 hrs increases neurofilament immunoreactivity and survival in cultured cortical neurons (Liu et al., SFN 2004). In this study, we report the utility of the Cellomics ArrayScan to characterize and quantify neurite outgrowth stimulated by immunophilin ligands in cultured cortical neurons and F-11 cells (rat dorsal root ganglia x mouse neuroblastoma hybrid). Cultured cortical neurons were treated ...