In the network of genes annotated to the cocaine pathway (also in the nicotine addiction pathway), ADCY5, DRD1, DRD2, PPP1R1B, and protein kinase C β (PRKCB) were over-expressed in Control nursed males relative to all pig groups with exception of Control weaned females (Figure 2). The gene discussed is DRD1; the disease is nicotine dependence.