Jodi I. Huggenvik

Effects of quitting smoking on EEG activation and attention last for more than 31 days and are more severe with stress, dependence, DRD2 A1 allele, and depressive traits

Changes in physiology and attentional performance associated with smoking abstinence were characterized in 67 female smokers during low-stress and high-stress conditions. Abstinence was associated with decreases in cognitive performance, heart rate, and electroencephalographic (EEG) activation but with no change in serum estradiol or progesterone. Effects of quitting showed no tendency to resolve across the 31 days of abstinence. EEG deactivation and heart rate slowing were greater during a math task (high stress) than during relaxation (low stress). Individuals high in trait depression or nicotine dependence or with at least one dopamine D(2) receptor A1 allele experienced greater EEG deactivation following abstinence, especially in the right hemisphere during the stressful task. Thus, findings support the situation x trait adaptive response model of abstinence effects and emphasize the value of multiple dependent measures when characterizing abstinence responses.

Gene-Environment Interactions Across Development: Exploring DRD2 Genotype and Prenatal Smoking Effects on Self-Regulation

Genetic factors dynamically interact with both pre- and postnatal environmental influences to shape development. Considerable attention has been devoted to gene-environment interactions (G x E) on important outcomes (A. Caspi & T. E. Moffitt, 2006). It is also important to consider the possibility that these G x E effects may vary across development, particularly for constructs like self-regulation that emerge slowly, depend on brain regions that change qualitatively in different developmental periods, and thus may be manifested differently. To illustrate one approach to exploring such developmental patterns, the relation between variation in the TaqIA polymorphism, related to D2 dopamine receptor expression and availability, and prenatal exposure to tobacco was examined in two exploratory studies. First, in 4-week-old neonates, genotype-exposure interactions were observed for attention and irritable reactivity, but not for stress dysregulation. Second, in preschool children, genotype was related to Preschool Trail Making Test (K. A. Espy and M. F. Cwik, 2004) task performance on conditions requiring executive control; children with both the A1+ genotype and a history of prenatal tobacco exposure displayed disproportionately poor performance. Despite study limitations, these results illustrate the importance of examining the interplay between genetic and prenatal environmental factors across development.

Nuclear DEAF-1-related (NUDR) Protein Contains a Novel DNA Binding Domain and Represses Transcription of the Heterogeneous Nuclear Ribonucleoprotein A2/B1 Promoter

Nuclear DEAF-1-related (NUDR) protein is a novel transcriptional regulator with sequence similarity to developmental and oncogenic proteins. NUDR protein deletions were used to localize the DNA binding domain between amino acids 167 and 368, and site-specific DNA photocross-linking indicated at least two sites of protein-DNA contact within this domain. The DNA binding domain contains a proline-rich region and a region with similarity to a Myc-type helix-loop-helix domain but does not include the zinc finger motif at the C terminus. Deoxyribonuclease I protection assays confirmed the presence of multiple NUDR binding motifs (TTC(C/G)G) in the heterogeneous nuclear ribonucleoprotein A2/B1 (hnRNP A2/B1) promoter and also in the 5′-untranslated region (UTR) of hNUDR cDNA. NUDR produced a 65–70% repression of the hnRNP A2/B1 promoter activity, and NUDR binding motifs in the 5′-UTR were found to mediate this repression. NUDR-dependent repression was also observed when the 5′-UTR of NUDR was placed onto a heterologous thymidine kinase promoter in an analogous 5′-UTR position but not when placed upstream of transcription initiation. These results suggest that NUDR may regulate the in vivo expression of hnRNP A2/B1 and NUDR genes and imply that inactivation of NUDR could contribute to the overexpression of hnRNP A2/B1 observed in some human cancers.

Dopamine Receptor (DRD2) Genotype-Dependent Effects of Nicotine on Attention and Distraction During Rapid Visual Information Processing

The effects of nicotine, distractor type, and dopamine type-2 receptor (DRD2) genotype on rapid visual information processing (RVIP) task performance were assessed in habitual smokers. Four RVIP tasks differed in terms of distractor location (central vs. peripheral) and distractor type (numeric vs. emotional). Each participant performed each of the tasks on two different days, once while wearing an active nicotine patch and once while wearing a placebo patch. Overall, the nicotine patch produced more accurate detection of and faster reaction times to target sequences; however, these effects varied with distractor type and genotype. Nicotine speeded reaction time more with left-visual-field (LVF) than right-visual-field (RVF) emotional distractors but speeded reaction time more with RVF than LVF numeric distractors, especially when the distractor digit matched the target sequence in terms of numeric oddness or evenness. Nicotine tended to facilitate performance more in individuals with at least one A1 allele than in homozygous A2A2 individuals, especially with numeric distractors presented to the left hemisphere. Nicotine tended to reduce distraction by negative stimuli more than other types of stimuli. Few gender differences were observed. The overall pattern of results was consistent with the view that nicotine modulates selective attention or subsequent information processing in a manner that depends partly on the emotional versus numeric nature of task distractors, DRD2 genotype, and the brain hemisphere that initially processes the distractors (visual field of distractor).

Neurotransmission-Related Genetic Polymorphisms, Negative Affectivity Traits, and Gender Predict Tobacco Abstinence Symptoms across 44 Days with and without Nicotine Patch

Genetic and personality trait moderators of tobacco abstinence-symptom trajectories were assessed in a highly controlled study. Based on evidence suggesting their importance in stress reactivity and smoking, moderators studied were serotonin transporter gene (5-HTTLPR) and dopamine D2 receptor gene (DRD2) polymorphisms and personality traits related to negative affect (NA). Smokers were randomly assigned to quit smoking with nicotine or placebo patches. Financial incentives resulted in 80% verified abstinence across the 44-day study. Individuals with 1 or 2 short alleles of 5-HTTLPR (S carriers) experienced larger increases in NA symptoms than did those without a short allele. Nicotine replacement therapy (NRT) alleviated anxiety only in S carriers. NRT reduced NA to a greater extent in DRD2 A1 carriers than in A2A2 individuals during the 1st 2 weeks of treatment (when on the 21-mg patch); however, A1 carriers experienced a renewal of NA symptoms when switched to the 7-mg patch and when off the patch, while A2A2 individuals continued to benefit from NRT. The results suggest that the effects of genotype and treatment may vary across different durations of abstinence, treatment doses, and genotypes.

DRD2 -related TaqIA polymorphism modulates motivation to smoke

INTRODUCTION TaqIA polymorphism, a genetic variant associated with the expression level of dopamine D2 receptors in the brain, has been linked to various aspects of smoking behavior, including smoking prevalence, affective withdrawal symptoms, and smoking cessation outcome. However, its involvement in motivation to smoke cigarettes has not been elucidated. METHODS The present study examined the possible differences in self-reported reasons to smoke and craving for smoking in 160 smokers participating in a clinical trial. RESULTS Individuals with at least one A1 allele of the TaqIA polymorphism were more likely to report smoking for stimulating effects and to reduce negative affect compared with those lacking an A1 allele. The association of the A1 genotype with a higher probability and stronger motive to smoker to enhance cognitive functioning was evident in female but not in male smokers. Female A1 carriers also expected a greater likelihood of smoking for pleasure than those without an A1 allele. A1 subjects reported stronger craving for cigarettes during early days and the last phase of a 6-week abstinence period. DISCUSSION These results support the idea that dopaminergic transmission plays an important role in the neurobiological basis of reasons for smoking and that the TaqIA variant is one of the genetic factors underlying individual differences in these aspects. These findings also have implications for improving treatment strategies to help individuals quit smoking by controlling their motivation to continue cigarette consumption.

Effects of Nicotine on Emotional Distraction of Attentional Orienting: Evidence of Possible Moderation by Dopamine Type 2 Receptor Genotype

INTRODUCTION Growing evidence suggests that attentional bias to, and distraction by, emotional stimuli may moderate affective states and motivation for nicotine and other drug use. METHODS The present study assessed the effects of nicotine and dopamine receptor genotype on distraction by emotional pictures, during a modified spatial attention task, in 46 overnight-deprived smokers. RESULTS Relative to placebo, 14mg nicotine patch produced shorter overall reaction times (RTs) and individuals with two dopamine type 2 receptor (DRD2) A2 alleles exhibited the greatest RT benefit from nicotine following emotionally negative pictures after the longest cue-target delay (800ms), but benefitted least from nicotine following positive pictures after the shortest delay (400ms). In contrast, at the shortest delay, A1 carriers did not benefit from nicotine following emotionally negative pictures but did following positive ones. CONCLUSIONS These genetic differences in the effects of nicotine on attention immediately following emotionally positive versus negative stimuli may reflect differential excitatory and inhibitory transmitter processes related to approach (reward) and avoidance (punishment) sensitivities of dopamine-related neural networks that support positive and negative affect.