Effects on cyclic AMP response element-binding protein (CREB). (A) Phosphorylated CREB expression (red fluorescence) and NeuN(green fluorescence) in hippocampus of a representative animal exposed to sleep fragmentation (SF) for 15 days and a control (n = 3). Right panel shows merged images. (B) Transcriptional CREB activity in untrained mice and in mice trained in the spatial task water maze (both exposed to SF for 15 days) compared with trained and untrained non-SF controls (P <0.01; n = 5/group). (C) Time course of phosphodiesterase (PDE) 4 gene expression in cortex of mice exposed to SF (P <0.01 for all time points; n = 6).