Figure 2. Concentration of serum corticosterone following sleep deprivation and treatment with RibCys and/or Zn.At p<0.05 level, a indicates significant differences from PSD, PSD+RibCys, PSD+Zn, PSD+RibCys+Zn and Control while d indicates a significant difference from Control. PSD=Paradoxical sleep deprivation, RibCys=Riboceine, Zn=Zinc.