The present study investigated the role of drug-paired stimuli in controlling the behavior of rhesus monkeys. Systematic observations were made with nine monkeys who had a history of drug self-administration; they had been lever pressing to produce intravenous infusions of various drugs. These observations revealed that the stimulus light co-occurring with drug infusion produced robust and cue-directed behavior such as orienting, touching and biting. Experiment 1 showed that this light-directed behavior would occur in naïve monkeys exposed to a Pavlovian pairing procedure. Four monkeys were given response-independent injections of cocaine. In two monkeys, a red light preceded cocaine injections by 5 s, and a green light co-occurred with the 5-s cocaine injections. In the other two monkeys, the light presentations and cocaine injections occurred independently. Light-directed behavior occurred in all four monkeys within the first couple of trials and at high levels but decreased across sessions. The cocaine-paired stimulus maintained behavior longer and at higher levels than the uncorrelated stimuli. Furthermore, light-directed behavior was not maintained when cocaine was replaced with saline. Light-directed behavior did not occur in the absence of the lights. When these monkeys were subsequently trained to lever press for cocaine, light-directed behavior increased to levels higher than previously observed. Behavior directed towards drug-paired stimuli is robust, reliable and multiply determined; the mechanisms underlying this activity likely include Pavlovian conditioning, stimulus novelty, habituation and operant conditioning.
Epidemiological and experimental evidence suggests that higher folate intake is associated with a decreased colorectal cancer (CRC) risk; however, the mechanisms underlying this relationship are not fully understood. Genetic variation that may have a direct or indirect impact on folate metabolism can provide insights into folate's role in CRC. Our aim was to perform a genome-wide interaction analysis to identify genetic variants that may modify the association of folate on CRC risk. We applied traditional case-control logistic regression, joint 3-degree of freedom (3DF), and a two-step weighted hypothesis approach to test the interactions of common variants (allele frequency >1%) across the genome and dietary folate, folic acid supplement use, and total folate in relation to risk of CRC, in 30,550 cases and 42,336 controls from 51 studies from 3 genetic consortia (CCFR, CORECT, GECCO). Inverse associations of dietary, total folate, and folic acid supplement with CRC were found [odds ratio: 0.93 (95% confidence intervals [CI]: 0.90-0.96), and 0.91 (0.89-0.94) per quartile higher intake, and 0.82 (0.78-0.88) for users vs. non-users, respectively]. Interactions (P-interaction <5×10-8) of folic acid supplement and variants in the 3p25.2 locus [in the region of Synapsin II (SYN2)/tissue inhibitor of metalloproteinase 4 (TIMP4)] were found using the traditional interaction analysis, with variant rs150924902 (located upstream to SYN2) showing the strongest interaction. In stratified analyses by rs150924902 genotypes, folate supplement was associated with decreased CRC risk among those carrying the TT genotype (OR = 0.82; 95%CI: 0.79-0.86) but increased CRC risk among those carrying the TA genotype (OR = 1.63; 95%CI: 1.29-2.05), suggesting a qualitative interaction (P-interaction = 1.4×10-8). No interactions were observed for dietary and total folate. Variation in 3p25.2 locus may modify the association of folate supplement with CRC risk. Experimental studies and studies incorporating other relevant -omics data are warranted to validate this finding.
<div>Abstract<p>Germline variation and smoking are independently associated with pancreatic ductal adenocarcinoma (PDAC). We conducted genome-wide smoking interaction analysis of PDAC using genotype data from four previous genome-wide association studies in individuals of European ancestry (7,937 cases and 11,774 controls). Examination of expression quantitative trait loci data from the Genotype-Tissue Expression Project followed by colocalization analysis was conducted to determine whether there was support for common SNP(s) underlying the observed associations. Statistical tests were two sided and <i>P</i> < 5 × 10<sup>–8</sup> was considered statistically significant. Genome-wide significant evidence of qualitative interaction was identified on chr2q21.3 in intron 5 of the transmembrane protein 163 (TMEM163) and upstream of the cyclin T2 (CCNT2). The most significant SNP using the Empirical Bayes method, in this region that included 45 significantly associated SNPs, was rs1818613 [per allele OR in never smokers 0.87, 95% confidence interval (CI), 0.82–0.93; former smokers 1.00, 95% CI, 0.91–1.07; current smokers 1.25, 95% CI 1.12–1.40, <i>P</i><sub>interaction</sub> = 3.08 × 10<sup>–9</sup>). Examination of the Genotype-Tissue Expression Project data demonstrated an expression quantitative trait locus in this region for TMEM163 and CCNT2 in several tissue types. Colocalization analysis supported a shared SNP, rs842357, in high linkage disequilibrium with rs1818613 (<i>r</i><sup>2</sup> = 0. 94) driving both the observed interaction and the expression quantitative trait loci signals. Future studies are needed to confirm and understand the differential biologic mechanisms by smoking status that contribute to our PDAC findings.</p>Significance:<p>This large genome-wide interaction study identifies a susceptibility locus on 2q21.3 that significantly modified PDAC risk by smoking status, providing insight into smoking-associated PDAC, with implications for prevention.</p></div>
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