Serum proteomic analysis during nicotine self-administration, extinction and relapse in rats

Nicotine dependence is known to induce long‐term neural adaptations in brain. The purpose of this study was to verify whether specific protein patterns related to nicotine self‐administration states could also be detected in a peripheral tissue. A serum proteomic analysis was performed by 2‐DE on samples taken at six time points: N, naïve; P, priming; S, self‐administration; W, withdrawal; E, extinction; R, relapse. After image analysis, spot volume values were submitted to a principal component analysis and relevant comparisons were selected. In N versus S; S versus W; E versus R; S versus R and S versus E comparisons a clear separation between groups could be observed, suggesting that each self‐administration state correlates with a specific protein expression pattern. Partial least squares discriminant analysis was adopted to rank proteins by the contribution to the overall separation. A number of spots were identified; among them, C reactive protein and haemopexin displayed a significant reduction after nicotine administration; two haemopexin isoforms were decreased in the S state and antithrombin III was increased in the E phase. This study showed that specific protein patterns related to the nicotine self‐administration states exist in serum. Further development of this approach may provide biomarkers to assess dependence states of drug‐taking individuals.