Figure 1.
Extinction of cocaine CPP increases Cav1.2 mRNA and protein in the hippocampus. A, Experimental timeline of the CPP protocol indicating the “CPP acquisition,” “CPP extinction,” and “CPP no extinction” groups used for behavioral and molecular studies. B, Cocaine-treated WT mice demonstrate robust acquisition of cocaine CPP as shown by significantly higher preference scores on acquisition versus baseline testing. After extinction training, these mice exhibit significantly lower preference scores on the extinction test day compared with the acquisition test day, indicating extinction of cocaine CPP. Control mice treated with saline did not show any changes in preference score when tested after acquisition and extinction training. *p < 0.05, **p < 0.01, ***p < 0.001 compared with baseline test; ###p < 0.001 compared with acquisition test. C, Extinction of cocaine CPP increased Cav1.2 (cacna1c) mRNA significantly in the hippocampus, but not in the PFC or NAc, compared with saline control mice. **p < 0.01. D, Extinction of cocaine CPP increased Cav1.2 protein levels significantly in the PSD-enriched fraction from the hippocampus, but not the PFC or NAc compared with saline controls. For quantitation of Cav1.2 protein, the doublet surrounding the predicted full-length 250 kDa protein was used. **p < 0.01. E, Cocaine-treated mice demonstrate robust CPP acquisition and sustained preference score in the absence of extinction training when retested 4 d later compared with baseline. Control mice treated with saline did not show any change in preference scores after testing on acquisition and a retest 4 d later. ***p < 0.001 compared with baseline test. F, Cav1.2 mRNA and PSD protein were unaltered in mice that underwent cocaine CPP acquisition after 4 d of home cage exposure without extinction training. Data are presented as mean ± SEM.