Our study of gene expression following long-access methamphetamine self-administration is now published in the International Journal of Molecular Sciences. Using RNA sequencing, we identified 41 differentially expressed genes in the prefrontal cortex and 32 in the hippocampus, spanning synaptic plasticity, immune response, and energy metabolism. Genes supporting mitochondrial function were downregulated, whereas genes involved in neural development and extracellular matrix organization were upregulated. Importantly, we then related this variability to economic demand for methamphetamine. Rats with higher demand showed distinct molecular profiles, including upregulation of Foxd1 and Cdh1. This analysis is preliminary, but it suggests that individual differences in drug taking may correspond to identifiable differences in gene expression.