Comparing cocaine exposure with alcohol exposure, our analysis (Zhou et al., 2011) of transcriptomes revealed a stronger shift in hippocampal mRNA expression in cocaine-addicted brains. This was manifested by both the larger number of differentially expressed genes (Fig. 10.1B) and changes in molecular and cellular functions defined by gene ontology. For example, the unidirectional depression of expression for the genes encoding for mitochondrial inner membrane and oxidative phosphorylation was only observed in the cocaine-addicted brain (Zhou et al., 2011). This strongly suggests that the inhibition is a specific effect of chronic cocaine exposure, with potential negative implications for brain energy metabolism and diverse brain functions that depend on it and with different metabolic consequences in alcoholism.
