Effect of pretreatment of HDAC inhibitors on c-Fos protein levels in the nucleus accumbens shell and prefrontal cortex of HAL-treated young and aged mice. Protein levels of c-Fos were determined by western blotting assay. Bands of c-Fos protein levels in the nucleus accumbens shell (a) and prefrontal cortex (c) are shown for the saline, HAL-, VPA-, HAL+VPA-, MS-275- and HAL+MS-275-treated groups of young and aged mice. Quantitative analysis of c-Fos protein levels is shown for both young (gray bars) and aged (black bars) mice of the nucleus accumbens shell (b) and prefrontal cortex (d). Data are presented as mean±SEM (n=4–5 per group). *p<0.05, **p<0.01, ***p<0.001.