GDNF levels were measured by ELISA in human cerebral cortex (CX), substantia nigra (SN), hippocampus (HP), and striatum (ST). Brain tissues of either sex were obtained from the National NeuroAIDS Tissue Consortium (NNTC). Samples were from: HIV negative subjects (control, n=4), HIV+ with normal neurocognitive diagnosis (HIV no HAD, n=7), HIV+ subjects with HAD (n=8), and HIV+ with neurological problems, caused by opportunistic infections, such as cytomegalovirus (HIV + neurological problems, n=7). Data are the mean ± SEM. More details about these subjects are given in Bachis et al., 2012. *p<0.01 vs HIV negative subjects (one-way ANOVA and Sheffe’s test).