DESCRIPTION:
Adult male C57BL/6J (B6) and DBA/2J (D2) mice (Jackson Laboratories, Bar Harbor, ME) 60–120 days old and weighing approximately 21–28 g at the start of the experiment were used. D2 (N = 12) and B6 (N = 27) mice were randomly distributed into three different yoked conditions. The self-administration experiment was run using a Yoked-control paradigm with three experimental groups (Yoker, Yoked-morphine, Yoked-saline). After recovery from surgery, the Yokers (subjects with contingent control over morphine injections) were given access to morphine (1mg/kg/injection) on a Fixed Ratio 4 (FR4) schedule of reinforcement in which they had to press the lever 4 times to receive one injection of morphine. Within each genotype, two yoked control animals were paired with the Yoker; one received an injection of 1.0 mg/kg morphine (Yoked-morphine) and the other received an injection of saline (Yoked-saline) each time the Yoker mouse self-injected morphine. All the stimulus conditions surrounding the injection were exactly the same for each member of the trio. Self-administration sessions ran for five days. Animals were housed in the operant chamber with free access to food and water. Each mouse was sacrificed by CO2 asphyxiation and decapitation. Immediately after decapitation the brain was removed and the tissue areas, Ventral Striatum (VS) and Ventral Midbrain (VMB), were dissected and placed in separate tubes with RNA later (Sigma-Aldrich, St. Louis, MO, USA). One group of B6 and D2 animals (N=12 per genotype, thus n=4 complete triads for each genotype) was utilized for behavioral phenotyping, gene expression profiling (microarray) and quantitative real time RT-PCR (qRT-PCR) validation of expression profiles. A second cohort of B6 animals (n = 5 complete triads) served as an independent group to further validate our behavioral results and microarray gene expression findings. The statistical comparisons between genotypes and graphical representations of the data were conducted on the first cohort, since these data represent a direct statistical association between global mRNA expression and behavior. The expression profiles of ~21,000 unique genes were measured in each of the two brain regions (VS and VMB) across the Yoked triad of the B6 and D2 genotypes. Genes exhibiting significant (10% FDR) condition-dependent differences in expression of ~1.4-fold or greater (between any 2 groups) were identified and referred to as significant yoked-condition (YC) B6 genes. FOM and k-means clustering was employed to identify the dominant expression profiles (across yoked conditions) in the YC gene set for the VS and VMB in B6 triads (refer to Supplemental Figure 3, panels A-H). This process identified eight main profiles (clusters A-H), and it should be noted that clusters beyond eight did not substantially improve the adjusted FOM score (Yeung et al., 2001). Four of the clusters (A, C-E) were eliminated from further consideration as a post-hoc t-test with 10% FDR indicated that the majority of genes in the Yokers were not significantly different from either the Yoked-morphine or Yoked-saline animals. These expression patterns would not be indicative of the endpoint we are specifically interested in -contingent self-administration behavior. Of the remaining clusters (B, F-H), B and H were remarkable as they contained genes that appeared to be negatively and positively correlated respectively with the behavioral profile of the B6 triad (compare Supplemental Figure 3B and H to Figure 3). In order to further refine our analysis, we subsequently used the B6 behavioral profile as a template to identify genes in clusters B and H having a significant match to the template (template match p-value < 0.05) (Figure 5), shown here from VS. From supplementary table 2.
LABEL:
Sig. B6 VS gene expression correlated with morphine SA: yoked-M vs yoker and yoked-S_log2FC
SCORE TYPE:
Effect
THRESHOLD:
<= 0.5
GENES IN THRESHOLD:
0
DATE ADDED:
DATE UPDATED:
SPECIES:
AUTHORS:
TITLE:
JOURNAL:
ABSTRACT:
Genes in threshold: 0
| Uploaded As | Gene Symbol | Homology | Score | Priority | LinkOuts | Emphasis |
|---|
GeneWeaver