Inhibition of monoamine oxidase B in the brains of smokers

Status and Future Directions of Preclinical Behavioral Pharmacology in Tobacco Regulatory Science

Behavioral pharmacology is a branch of the experimental analysis of behavior that has had great influence in drug addiction research and policy. This paper provides an overview of recent behavioral pharmacology research in the field of tobacco regulatory science, which provides the scientific foundation for the Food and Drug Administration Center for Tobacco Products (FDA CTP) to set tobacco control policies. The rationale and aims of tobacco regulatory science are provided, including the types of preclinical operant behavioral models it deems important for assessing the abuse liability of tobacco products and their constituents. We then review literature relevant to key regulatory actions being considered by the FDA CTP, including regulations over nicotine and menthol content of cigarettes, and conclude with suggesting some directions for future research. The current era of tobacco regulatory science provides great opportunities for behavioral pharmacologists to address the leading cause of preventable death and disease worldwide.

Perinatal MAO Inhibition Produces Long-Lasting Impairment of Serotonin Function in Offspring

In addition to transmitter functions, many neuroamines have trophic or ontogenetic regulatory effects important to both normal and disordered brain development. In previous work (Mejia et al., 2002), we showed that pharmacologically inhibiting monoamine oxidase (MAO) activity during murine gestation increases the prevalence of behaviors thought to reflect impulsivity and aggression. The goal of the present study was to determine the extent to which this treatment influences dopamine and serotonin innervation of murine cortical and subcortical areas, as measured by regional density of dopamine (DAT) and serotonin transporters (SERT). We measured DAT and SERT densities at 3 developmental times (PND 14, 35 and 90) following inhibition of MAO A, or MAO B or both throughout murine gestation and early post-natal development. DAT binding was unaltered within the nigrostriatal pathway, but concurrent inhibition of MAO-A and MAO-B significantly and specifically reduced SERT binding by 10–25% in both the frontal cortex and raphe nuclei. Low levels of SERT binding persisted (PND 35, 90) after the termination (PND 21) of exposure to MAO inhibitors and was most marked in brain structures germane to the previously described behavioral changes. The relatively modest level of enzyme inhibition (25–40%) required to produce these effects mandates care in the use of any compound which might inhibit MAO activity during gestation.

Animal Research on Nicotine Reduction: Current Evidence and Research Gaps

A mandated reduction in the nicotine content of cigarettes may improve public health by reducing the prevalence of smoking. Animal self-administration research is an important complement to clinical research on nicotine reduction. It can fill research gaps that may be difficult to address with clinical research, guide clinical researchers about variables that are likely to be important in their own research, and provide policy makers with converging evidence between clinical and preclinical studies about the potential impact of a nicotine reduction policy. Convergence between clinical and preclinical research is important, given the ease with which clinical trial participants can access nonstudy tobacco products in the current marketplace. Herein, we review contributions of preclinical animal research, with a focus on rodent self-administration, to the science of nicotine reduction. Throughout this review, we highlight areas where clinical and preclinical research converge and areas where the two differ. Preclinical research has provided data on many important topics such as the threshold for nicotine reinforcement, the likelihood of compensation, moderators of the impact of nicotine reduction, the impact of environmental stimuli on nicotine reduction, the impact of nonnicotine cigarette smoke constituents on nicotine reduction, and the impact of nicotine reduction on vulnerable populations. Special attention is paid to current research gaps including the dramatic rise in alternative tobacco products, including electronic nicotine delivery systems (ie, e-cigarettes). The evidence reviewed here will be critical for policy makers as well as clinical researchers interested in nicotine reduction.

IMPLICATIONS

This review will provide policy makers and clinical researchers interested in nicotine reduction with an overview of the preclinical animal research conducted on nicotine reduction and the regulatory implications of that research. The review also highlights the utility of preclinical research for research questions related to nicotine reduction.

Psychological, pharmacological, and combined smoking cessation interventions for smokers with current depression: A systematic review and meta-analysis

We conducted a systematic literature review and meta-analysis (ID: CRD42016051017) of smoking cessation interventions for patients with current depression. We examined the effectiveness of smoking cessation treatments in improving abstinence rates and depressive symptoms. The following electronic databases were used for potentially eligible studies: PUBMED, PSYCINFO, DIALNET and WEB OF KNOWLEDGE. The search terms used were: smoking cessation, depressive disorder, depression, mood, depressive, depressed, smoking, smokers, nicotine, nicotine dependence, and tobacco cigarette smoking. The methodological quality of included studies was assessed using the Effective Public Health Practice Project Quality assessment tool (EPHPP). Of the 6,584 studies identified, 20 were eligible and included in the review. Trial designs of studies were 16 randomized controlled trials and 4 secondary studies. Studies included three types of intervention: psychological (6/30%), pharmacological (6/30%) or combined (8/40%). Four trials comprised special populations of smokers. Four studies received a strong methodological quality, 7 were scored as moderate and 9 studies received a weak methodological rating. Analyses of effectiveness showed that smoking cessation interventions appear to increase short-term and long-term smoking abstinence in individuals with current depression. Subgroup analyses revealed stronger effects among studies that provided pharmacological treatments than in studies using psychological treatments. However, the evidence is weak due to the small number of studies. Smoking abstinence appears to be associated with an improvement in depressive symptoms. Heterogeneity in protocols in similar types of treatment also prevent firm conclusions being drawn on the effectiveness of any particular treatment model to optimally manage abstinence among depressed smokers. Further research is required to strengthen the evidence base.

Subjective experiences at first use of cigarette, e-cigarettes, hookah, and cigar products among Texas adolescents

INTRODUCTION

Subjective experiences ("SEs") at first cigarette use have been thoroughly examined; however, limited research has examined SEs at first use of non-cigarette products. This study addresses this gap in the literature.

METHODS

Cross-sectional data from 6th, 8th and 10th grade students in four metropolitan areas of Texas (n=3907/N=461,069). Nausea, coughing, relaxation, rush/buzz, and dizziness at first use were assessed for cigarettes, e-cigarettes, hookah, and cigar products. Chi-square analyses examined differences in the prevalence of first use SEs by product. Weighted multiple logistic regression analyses examined the association of SEs and current product use. Covariates were grade, gender, race/ethnicity, and current other tobacco product use.

RESULTS

Exploratory factor analysis of SEs determined differing factor structures across tobacco products. For example, the following items loaded onto the positive SE factor: 1) relaxation, rush, and dizziness for cigarettes, and 2) relaxation and rush for e-cigarettes, hookah, and cigar products. Prevalence of negative SEs (coughing and nausea) were higher for cigarette and cigar products compared to e-cigarettes and hookah. Positive SEs for cigarettes were associated with increased odds of current cigarette use (AOR=1.51); similarly positive SEs for cigars were associated with increased odds of current cigar use (AOR=2.11). Feeling nauseous at first use of cigars was associated with decreased odds of current cigar use (AOR=0.18). No SEs were associated with current e-cigarette or hookah use.

CONCLUSIONS

Subjective experiences at first use differ by tobacco product. Longitudinal studies are needed to examine temporal relationships between SEs at first use and sustained tobacco use.

Monoamine oxidase B inhibitor, selegiline, reduces 18F-THK5351 uptake in the human brain

Background

¹⁸F-THK5351 is a quinoline-derived tau imaging agent with high affinity to paired helical filaments (PHF). However, high levels of ¹⁸F-THK5351 retention in brain regions thought to contain negligible concentrations of PHF raise questions about the interpretation of the positron emission tomography (PET) signals, particularly given previously described interactions between quinolone derivatives and monoamine oxidase B (MAO-B). Here, we tested the effects of MAO-B inhibition on ¹⁸F-THK5351 brain uptake using PET and autoradiography.

Methods

Eight participants (five mild cognitive impairment, two Alzheimer’s disease, and one progressive supranuclear palsy) had baseline ¹⁸F-AZD4694 and ¹⁸F-THK5351 scans in order to quantify brain amyloid and PHF load, respectively. A second ¹⁸F-THK5351 scan was conducted 1 week later, 1 h after a 10-mg oral dose of selegiline. Three out of eight patients also had a third ¹⁸F-THK5351 scan 9–28 days after the selegiline administration. The primary outcome measure was standardized uptake value (SUV), calculated using tissue radioactivity concentration from 50 to 70 min after ¹⁸F-THK5351 injection, normalizing for body weight and injected radioactivity. The SUV ratio (SUVR) was determined using the cerebellar cortex as the reference region. ¹⁸F-THK5351 competition autoradiography studies in postmortem tissue were conducted using 150 and 500 nM selegiline.

Results

At baseline, ¹⁸F-THK5351 SUVs were highest in the basal ganglia (0.64 ± 0.11) and thalamus (0.62 ± 0.14). In the post-selegiline scans, the regional SUVs were reduced on average by 36.7% to 51.8%, with the greatest reduction noted in the thalamus (51.8%) and basal ganglia (51.4%). MAO-B inhibition also reduced ¹⁸F-THK5351 SUVs in the cerebellar cortex (41.6%). The SUVs remained reduced in the three patients imaged at 9–28 days. Tissue autoradiography confirmed the effects of MAO-B inhibition on ¹⁸F-THK5351 uptake.

Conclusions

These results indicate that the interpretation of ¹⁸F-THK5351 PET images, with respect to tau, is confounded by the high MAO-B availability across the entire brain. In addition, the heterogeneous MAO-B availability across the cortex may limit the interpretation of ¹⁸F-THK5351 scans using reference region methods.

Oxidative and inert pyrolysis on-line coupled to gas chromatography with mass spectrometric detection: On the pyrolysis products of tobacco additives

According to European legislation, tobacco additives may not increase the toxicity or the addictive potency of the product, but there is an ongoing debate on how to reliably characterize and measure such properties. Further, too little is known on pyrolysis patterns of tobacco additives to assume that no additional toxicological risks need to be suspected. An on-line pyrolysis technique was used and coupled to gas chromatography-mass spectrometry (GC/MS) to identify the pattern of chemical species formed upon thermal decomposition of 19 different tobacco additives like raw cane sugar, licorice or cocoa. To simulate the combustion of a cigarette it was necessary to perform pyrolysis at inert conditions as well as under oxygen supply. All individual additives were pyrolyzed under inert or oxidative conditions at 350, 700 and 1000°C, respectively, and the formation of different toxicants was monitored. We observed the generation of vinyl acrylate, fumaronitrile, methacrylic anhydride, isobutyric anhydride and 3-buten-2-ol exclusively during pyrolysis of tobacco additives. According to the literature, these toxicants so far remained undetectable in tobacco or tobacco smoke. Further, the formation of 20 selected polycyclic aromatic hydrocarbons (PAHs) with molecular weights of up to 278Da was monitored during pyrolysis of cocoa in a semi-quantitative approach. It was shown that the adding of cocoa to tobacco had no influence on the relative amounts of the PAHs formed.

Translational potential of astrocytes in brain disorders

Fundamentally, all brain disorders can be broadly defined as the homeostatic failure of this organ. As the brain is composed of many different cells types, including but not limited to neurons and glia, it is only logical that all the cell types/constituents could play a role in health and disease. Yet, for a long time the sole conceptualization of brain pathology was focused on the well-being of neurons. Here, we challenge this neuron-centric view and present neuroglia as a key element in neuropathology, a process that has a toll on astrocytes, which undergo complex morpho-functional changes that can in turn affect the course of the disorder. Such changes can be grossly identified as reactivity, atrophy with loss of function and pathological remodeling. We outline the pathogenic potential of astrocytes in variety of disorders, ranging from neurotrauma, infection, toxic damage, stroke, epilepsy, neurodevelopmental, neurodegenerative and psychiatric disorders, Alexander disease to neoplastic changes seen in gliomas. We hope that in near future we would witness glial-based translational medicine with generation of deliverables for the containment and cure of disorders. We point out that such as a task will require a holistic and multi-disciplinary approach that will take in consideration the concerted operation of all the cell types in the brain.

Effects of Monoamine Oxidase Inhibition on the Reinforcing Properties of Low-Dose Nicotine

The Food and Drug Administration (FDA) has the authority to regulate cigarette smoke constituents, and a reduction in nicotine content might benefit public health by reducing the prevalence of smoking. Research suggests that cigarette smoke constituents that inhibit monoamine oxidase (MAO) may increase the reinforcing value of low doses of nicotine. The aim of the present experiments was to further characterize the impact of MAO inhibition on the primary reinforcing and reinforcement enhancing effects of nicotine in rats. In a series of experiments, rats responded for intravenous nicotine infusions or a moderately-reinforcing visual stimulus in daily 1-h sessions. Rats received pre-session injections of known MAO inhibitors. The results show that (1) tranylcypromine (TCP), a known MAO inhibitor, increases sensitivity to the primary reinforcing effects of nicotine, shifting the dose-response curve for nicotine to the left, (2) inhibition of MAO-A, but not MAO-B, increases low-dose nicotine self-administration, (3) partial MAO-A inhibition, to the degree observed in chronic cigarette smokers, also increases low-dose nicotine self-administration, and (4) TCP decreases the threshold nicotine dose required for reinforcement enhancement. The results of the present experiments suggest cigarette smoke constituents that inhibit MAO-A, in the range seen in chronic smokers, are likely to increase the primary reinforcing and reinforcement enhancing effects of low doses of nicotine. If the FDA reduces the nicotine content of cigarettes, then variability in constituents that inhibit MAO-A could impact smoking.

Molecular aspects of monoamine oxidase B

Monoamine oxidases (MAO) influence the monoamine levels in brain by virtue of their role in neurotransmitter breakdown. MAO B is the predominant form in glial cells and in platelets. MAO B structure, function and kinetics are described as a background for the effect of alterations in its activity on behavior. The need to inhibit MAO B to combat decreased brain amines continues to drive the search for new drugs. Reversible and irreversible inhibitors are now designed using data-mining, computational screening, docking and molecular dynamics. Multi-target ligands designed to combat the elevated activity of MAO B in Alzheimer's and Parkinson's Diseases incorporate MAO inhibition (usually irreversible) as well as iron chelation, antioxidant or neuroprotective properties. The main focus of drug design is the catalytic activity of MAO, but the imidazoline I2 site in the entrance cavity of MAO B is also a pharmacological target. Endogenous regulation of MAO B expression is discussed briefly in light of new studies measuring mRNA, protein, or activity in healthy and degenerative samples, including the effect of DNA methylation on the expression. Overall, this review focuses on examples of recent research on the molecular aspects of the expression, activity, and inhibition of MAO B.

The role of MAO in personality and drug use

Monoamine oxidases, both MAO-A and MAO-B, have been implicated in personality traits and complex behaviour, including drug use. Findings supporting the involvement of MAO-A and MAO-B in shaping personality and in the development of strategies of making behavioural choices come from a variety of studies that have examined either prevalence of gene variants in clinical groups or population-derived samples, estimates of enzyme activity in blood or, by positron emission tomography, in the brain and, most recently, measurement of methylation of the gene. Most of the studies converge in associating MAO-A and MAO-B with impulsive, aggressive or antisocial personality traits or behaviours, including alcohol-related problems, and for MAO-A available evidence strongly supports interaction with adverse environmental exposures in childhood. What is known about genotype effects, and on expression and activity of the enzyme in the brain and in blood has not yet been possible to unite into a mechanistic model of the role of monoamine systems, but the reason for this low degree of generalization is likely caused by the cross-sectional nature of investigation that has not incorporated the developmental effects of MAO-s in critical time windows, including the foetal period. The "risk variants" of both MAO-s appear to increase behavioural plasticity, as supportive environments may particularly well enhance the hidden potential of their carriers. Importantly, male and female brain and behaviours have been found very different with regard to MAO×life events interaction. Future studies need to take into consideration these developmental aspects and sex/gender, as well as to specify the role of different types of environmental factors.

The influence of tobacco smoke and nicotine on antidepressant and memory-improving effects of venlafaxine

In experimental and clinical studies, central nicotinic systems have been shown to play an important role in cognitive function. Nicotinic acetylcholine receptors also mediate the reinforcing properties of nicotine (NIC) in tobacco products. A variety of studies have shown that acute treatment with NIC or nicotinic agonists can improve working memory function. Moreover, it is known that the monoaminergic system plays an important role in memory function. And there is evidence suggesting that prolonged use of NIC may exert antidepressant action via nicotinic receptors. The purpose of this study was to investigate the interactions between a novel antidepressant, venlafaxine (VEN), a blocker of noradrenaline and 5–hydroxytryptamine reuptake sites, and pure NIC in the context of antidepressant and memory function in tobacco smoke exposed and nonexposed rats. The animals were subjected to Porsolt's test for testing antidepressant activity and their memory function (spatial memory) was evaluated in the Morris Water Maze Test. In tobacco smoke non–exposed and exposed rats both single and chronic administration of VEN (20 mg/kg po) shortened immobility time. NIC (0.2 mg/kg sc) significantly reduced immobility time on the 1st, 7th and 14th test days in both non–exposed and exposed rats. Combined VEN–NIC treatment in tobacco smoke non–exposed rats reduced immobility too. This effect of the combination of drugs was significantly stronger as compared to the effects obtained after individual administration of VEN or NIC. In the group exposed to tobacco smoke, joint administration of VEN–NIC induced a significant reduction of immobility as compared to the control and NIC groups. In the Morris Water Maze Test single and chronic administration of VEN, lower values of escape latencies and lower numbers of crossed quadrants were noted in both exposed and non–exposed rats, which indicates improved performance. After administering NIC we could observe improvement of spatial memory in both the exposed and non–exposed group. A similar effect of improvement of spatial memory was observed after joint administration of VEN and NIC. The study results support the involvement of nicotinic systems in memory processes in rats. Memory improvement and antidepressant effects following joint administration of VEN and NIC may depend on nicotinic interactions with monoaminergic systems and VEN may represent a new therapeutic approach to smoking cessation.

Smoking and haptoglobin phenotype modulate serum ferritin and haptoglobin levels in Parkinson disease

The phenotype Hp 2-1 of haptoglobin has been previously associated with increased risk of Parkinson disease (PD) and with serum iron abnormalities in PD patients. Tobacco smoking has been consistently observed in epidemiology studies to be inversely related to PD risk, with mechanisms that remain uncertain. We recently observed that the protective effect of smoking on PD risk is stronger among subjects of haptoglobin Hp 2-2 and Hp 1-1 phenotypes, and weaker among subjects of haptoglobin Hp 2-1 phenotype. In this PD case-control study, we investigated whether tobacco smoking was associated with changes in serum haptoglobin and ferritin concentration that depended on haptoglobin phenotype among 106 PD patients and 238 controls without PD or other neurodegenerative disorders. Serum ferritin concentration, serum haptoglobin concentration, haptoglobin phenotype, and smoking data information of cases and controls were obtained. Differences in haptoglobin and ferritin concentration by smoking status and pack-years of smoking were calculated as well as regression between pack-years and haptoglobin and ferritin concentration, and the effect of haptoglobin phenotype on these parameters. Tobacco smoking was associated with an elevation in serum haptoglobin concentration, especially among healthy controls of haptoglobin Hp 2-2 phenotype, and with an elevation in ferritin concentration especially among PD patients of haptoglobin Hp 2-1 phenotype. These findings suggest that an elevation in haptoglobin concentration, preferentially among subjects of haptoglobin Hp 2-2 phenotype, could be a contributing factor to the protective effect of smoking on PD risk.

Association between Parkinson's Disease and Cigarette Smoking, Rural Living, Well-Water Consumption, Farming and Pesticide Use: Systematic Review and Meta-Analysis

Objective

Bradford Hill’s viewpoints were used to conduct a weight-of-the-evidence assessment of the association between Parkinson’s disease (PD) and rural living, farming and pesticide use. The results were compared with an assessment based upon meta-analysis. For comparison, we also evaluated the association between PD and cigarette smoking as a “positive control” because a strong inverse association has been described consistently in the literature.

Methods

PubMed was searched systematically to identify all published epidemiological studies that evaluated associations between Parkinson’s disease (PD) and cigarette smoking, rural living, well-water consumption, farming and the use of pesticides, herbicides, insecticides, fungicides or paraquat. Studies were categorized into two study quality groups (Tier 1 or Tier 2); data were abstracted and a forest plot of relative risks (RRs) was developed for each risk factor. In addition, when available, RRs were tabulated for more highly exposed individuals compared with the unexposed. Summary RRs for each risk factor were calculated by meta-analysis of Tier 1, Tier 2 and all studies combined, with sensitivity analyses stratified by other study characteristics. Indices of between-study heterogeneity and evidence of reporting bias were assessed. Bradford Hill’s viewpoints were used to determine if a causal relationship between PD and each risk factor was supported by the weight of the evidence.

Findings

There was a consistent inverse (negative) association between current cigarette smoking and PD risk. In contrast, associations between PD and rural living, well-water consumption, farming and the use of pesticides, herbicides, insecticides, fungicides or paraquat were less consistent when assessed quantitatively or qualitatively.

Conclusion

The weight of the evidence and meta-analysis support the conclusion that there is a causal relationship between PD risk and cigarette smoking, or some unknown factor correlated with cigarette smoking. There may be risk factors associated with rural living, farming, pesticide use or well-water consumption that are causally related to PD, but the studies to date have not identified such factors. To overcome the limitations of research in this area, future studies will have to better characterize the onset of PD and its relationship to rural living, farming and exposure to pesticides.

How can we Improve on Modeling Nicotine Addiction to Develop Better Smoking Cessation Treatments?

Clinically effective smoking cessation treatments are few in number, mainly varenicline, bupropion, and nicotine replacement therapy being prescribed by health organizations. Of the many compounds tested for smoking cessation, a good proportion fail in human trials despite positive findings in rodents. This chapter aims to cover the uses and some pit falls of current methodologies employed to discover clinical treatments in the laboratory. Complicating factors include the complex nature of genetics in tobacco smoking and the comorbidity associated with other psychiatric disorders, which has not been addressed fully in the rodent laboratory. This chapter reviews the evidence from intravenous nicotine self-administration studies and proposes modifications on how we can improve the validity of the animal models by incorporating clinically relevant factors considered to be critical in tobacco smoking. For example, choice procedures that incorporate alternative reinforcers, use of reinstatement models, and second-order schedules of reinforcement are proposed to have better scientific validity that may lead to better clinical outcomes. Furthermore, improved experimental methods will also improve our chances of discovering effective treatments that ultimately may mitigate the effects of tobacco smoking with regard to health worldwide.

An Inventory of Methods for the Assessment of Additive Increased Addictiveness of Tobacco Products

BACKGROUND

Cigarettes and other forms of tobacco contain the addictive drug nicotine. Other components, either naturally occurring in tobacco or additives that are intentionally added during the manufacturing process, may add to the addictiveness of tobacco products. As such, these components can make cigarette smokers more easily and heavily dependent.Efforts to regulate tobacco product dependence are emerging globally. Additives that increase tobacco dependence will be prohibited under the new European Tobacco Product Directive.

OBJECTIVE

This article provides guidelines and recommendations for developing a regulatory strategy for assessment of increase in tobacco dependence due to additives. Relevant scientific literature is summarized and criteria and experimental studies that can define increased dependence of tobacco products are described.

CONCLUSIONS

Natural tobacco smoke is a very complex matrix of components, therefore analysis of the contribution of an additive or a combination of additives to the level of dependence on this product is challenging. We propose to combine different type of studies analyzing overall tobacco product dependence potential and the functioning of additives in relation to nicotine. By using a combination of techniques, changes associated with nicotine dependence such as behavioral, physiological, and neurochemical alterations can be examined to provide sufficient information.Research needs and knowledge gaps will be discussed and recommendations will be made to translate current knowledge into legislation. As such, this article aids in implementation of the Tobacco Product Directive, as well as help enable regulators and researchers worldwide to develop standards to reduce dependence on tobacco products.

IMPLICATIONS

This article provides an overall view on how to assess tobacco product constituents for their potential contribution to use and dependence. It provides guidelines that help enable regulators worldwide to develop standards to reduce dependence on tobacco products and guide researches to set research priorities on this topic.

The separate and combined effects of monoamine oxidase A inhibition and nicotine on resting state EEG

While nicotine is often associated with the neuropsychological effects of tobacco smoke, the robust monoamine oxidase (MAO) inhibition observed in chronic smokers is also likely to play a role. Electroencephalographically-indexed alterations in baseline neural oscillations by nicotine have previously been reported in both smokers and non-smokers, however, little is known about the effects of MAO inhibition in combination with nicotine on resting state EEG. In a sample of 24 healthy non-smoking males, the effects of 6 mg nicotine gum, as well as MAO-A inhibition via 75 mg moclobemide, were investigated in separate and combined conditions over four separate test sessions. Drug effects were observed in the alpha2, beta2, and theta band frequencies. Nicotine increased alpha2 power, and moclobemide decreased beta2 power. Theta power was decreased most robustly by the combination of both drugs. Therefore, this study demonstrated that the nicotinic and MAO inhibiting properties of tobacco may differentially influence fast-wave oscillations (alpha2 and beta2), while acting in synergy to influence theta oscillations.

Family Smoking, Exposure to Secondhand Smoke at Home and Family Unhappiness in Children

Tobacco use adversely affects many aspects of well-being and is disliked by non-smokers. However, its association with family happiness is unknown. We investigated the associations of family unhappiness with smoking in family members and secondhand smoke (SHS) exposure at home in Hong Kong children. In a school-based survey in 2012–2013, 1238 primary school students (mean age 8.5 years, standard deviation 0.9; 42.6% boys) reported family smoking, SHS exposure at home and whether their families had any unpleasant experience caused by smoking or SHS in the past 30 days (tobacco-related unpleasant experience), and rated the overall level of happiness in their families (family unhappiness). Multivariable logistic regression was used to study the associations of tobacco-related unpleasant experience and family unhappiness with family smoking and SHS exposure at home. Tobacco-related unpleasant experience and family unhappiness were reported by 27.5% and 16.5% of students. Unpleasant experience was more strongly associated with family smoking than SHS exposure at home. Family unhappiness was associated with both family smoking (odds ratio 2.37; 95% confidence interval 1.51–3.71) and SHS exposure at home (1.82; 1.39–2.40). These results suggest a previously neglected possible impact of tobacco use on family happiness.

Contribution of Monoamine Oxidase Inhibition to Tobacco Dependence: A Review of the Evidence

BACKGROUND

There is a hypothesis that substances present in, or derived from, tobacco smoke inhibit monoamine oxidase (MAO) in the brains of smokers, reducing the degradation of catecholamine neurotransmitters involved in central reward pathways and acting synergistically with nicotine to increase its addictive effects.

OBJECTIVE

The objective of this review was to evaluate the evidence for a role of MAO inhibition by tobacco-derived substances in tobacco dependence.

INVESTIGATIONAL PLAN

Relevant studies on the effects of tobacco use on MAO levels or activity in humans were identified by electronic searches.

RESULTS

The identified data show a clear association between smoking and lower density of MAO-A and MAO-B binding sites in the brains of smokers and strong evidence that MAO is inhibited by a substance or substances in, or derived from, tobacco smoke. There was little evidence to support the hypothesis that low MAO levels/activity is a predictive factor for tobacco use. Substances that inhibit MAO in in vitro assays have been isolated from tobacco leaves and tobacco smoke; however, no single substance has been shown to be absorbed from tobacco smoke and to inhibit MAO in the brains of human smokers. Nevertheless, it is possible that MAO inhibition in smokers could result from additive or synergistic effects of several tobacco-derived substances. MAO inhibition potentiates the reinforcing effects of intravenous nicotine in rodents; however, no data were identified to support the hypothesis that MAO inhibitors in or derived from tobacco or tobacco additives affect tobacco dependence in human smokers.

IMPLICATIONS

This comprehensive review describes the available evidence for the role of MAO inhibition in tobacco dependence and points the way for further research in this field. In view of the large number of MAO inhibitors identified in tobacco and tobacco smoke, identification of the putative inhibitors responsible for the lower level/activity of MAO in smokers may be impractical. Future studies must address whether the lower level/activity of MAO observed in smokers is also seen in users of other tobacco products and if this change is implicated in their dependence-inducing effects.

Bacoside A: Role in Cigarette Smoking Induced Changes in Brain

Cigarette smoking (CS) is a major health hazard that exerts diverse physiologic and biochemical effects mediated by the components present and generated during smoking. Recent experimental studies have shown predisposition to several biological consequences from both active and passive cigarette smoke exposure. In particular, passive smoking is linked to a number of adverse health effects which are equally harmful as active smoking. A pragmatic approach should be considered for designing a pharmacological intervention to combat the adverse effects of passive smoking. This review describes the results from a controlled experimental condition, testing the effect of bacoside A (BA) on the causal role of passive/secondhand smoke exposure that caused pathological and neurological changes in rat brain. Chronic exposure to cigarette smoke induced significant changes in rat brain histologically and at the neurotransmitter level, lipid peroxidation states, mitochondrial functions, membrane alterations, and apoptotic damage in rat brain. Bacoside A is a neuroactive agent isolated from Bacopa monnieri. As a neuroactive agent, BA was effective in combating these changes. Future research should examine the effects of BA at molecular level and assess its functional effects on neurobiological and behavioral processes associated with passive smoke.

The separate and combined effects of monoamine oxidase A inhibition and nicotine on the mismatch negativity event related potential

The mismatch negativity (MMN) auditory event-related potential (ERP) has been extensively studied as a potential biomarker for abnormal auditory processing in schizophrenia (SZ), a population which exhibits abnormally high smoking rates. The relationship between nicotinic activation and cognition in SZ may be related to underlying nicotinic and NMDA receptor dysfunction within the disease. However, transient cognitive improvements via smoking in patients may also result from monoamine oxidase (MAO) inhibition, achieved through tobacco smoke. In 24 healthy non-smoking males, we investigated the separate and combined effects of nicotine and MAO-A inhibition via moclobemide (75mg) on the optimal-5 variation of the MMN paradigm. No significant drug effects were observed in our total sample, however, stratification of individuals into low (N=12) and high (N=12) baseline MMN amplitude groups revealed increases in duration MMN amplitude relative to placebo by nicotine, as well as moclobemide, but not after the combination of the two. Because previous research has shown there was no effect of monoamine modulation on MMN, this study shows an unexpected effect of moclobemide on duration MMN.

Imaging of monoamine oxidase-A in the human brain with [11C]befloxatone: quantification strategies and correlation with mRNA transcription maps

INTRODUCTION

[C]Befloxatone is a highly specific, reversible, and selective radioligand for brain PET imaging of monoamine oxidase-A and can be quantified by a two-tissue compartment model (2TCM) and an arterial input function. The aims of the present study were the following: (a) to assess whether in-vivo protein concentration, as measured by [C]befloxatone total distribution volume (VT), is correlated with post-mortem mRNA expression; (b) to replicate in a population of tobacco smokers the results of a recent study on healthy nonsmokers, which showed that spectral analysis (SA) provides a highly accurate estimation of [C]befloxatone-VT at the voxel level; and (c) to validate the use of an input function that would not require arterial sampling.

MATERIALS AND METHODS

Healthy male nonsmokers (n=7) and smokers (n=8) were imaged with PET and [C]befloxatone. Binding was quantified at the regional and voxel level with the Logan plot, multilinear analysis (MA1), and SA. VT values were compared with the reference values obtained by 2TCM at the regional level. [C]Befloxatone binding was compared with mRNA transcription maps from the Allen Human Brain Atlas. A less-invasive input function was obtained with a population-based input function (PBIF) scaled with arterialized venous samples.

RESULTS

mRNA expression was highly correlated with in-vivo 2TCM-VT values both for nonsmokers (R=0.873; P<0.0001) and for smokers (R=0.851; P<0.0001). At the regional level, both Logan and MA1 showed a moderate negative bias (-5 to -10%) compared with the reference VT values. With the exception of a single outlying individual, SA showed little bias and variability (+4.4±3.5%). Although variability was higher than at the regional level, SA provided the most accurate VT estimations at the voxel level: all but one participant had an error of less than 20%. Parametric Logan and MA1 analyses gave highly biased or unusable results. PBIF provided good results in all participants in whom the arterialization of venous blood was successful (all errors of about 10% or less).

CONCLUSION

[C]Befloxatone binding is strongly correlated with the values of mRNA transcription measured in post-mortem brains. At the voxel level, SA is the best available choice for [C]befloxatone quantification, although a higher variability must be expected. When an arterial input function is not technically feasible, a PBIF scaled with arterialized venous samples may provide an acceptable alternative, provided an optimal arterialization can be achieved.

Brain imaging changes associated with risk factors for cardiovascular and cerebrovascular disease in asymptomatic patients

Reviews of imaging studies assessing the brain effects of vascular risk factors typically include a substantial number of studies with subjects with a history of symptomatic cardiovascular or cerebrovascular disease and/or events, limiting our ability to disentangle the primary brain effects of vascular risk factors from those of resulting brain and cardiac damage. The objective of this study was to perform a systematic review of brain changes from imaging studies in patients with vascular risk factors but without clinically manifest cardiovascular or cerebrovascular disease or events. The 77 studies included in this review demonstrate that in persons without symptomatic cardiovascular, cerebrovascular, or peripheral vascular disease, the vascular risk factors of hypertension, diabetes mellitus, obesity, hyperlipidemia, and smoking are all independently associated with brain imaging changes before the clinical manifestation of cardiovascular or cerebrovascular disease. We conclude that the identification of brain changes associated with vascular risk factors, before the manifestation of clinically significant cerebrovascular damage, presents a window of opportunity wherein adequate treatment of these modifiable vascular risk factors may prevent the development of irreversible deleterious brain changes and potentially alter patients' clinical course.

The dopamine theory of addiction: 40 years of highs and lows

For several decades, addiction has come to be viewed as a disorder of the dopamine neurotransmitter system; however, this view has not led to new treatments. In this Opinion article, we review the origins of the dopamine theory of addiction and discuss the ability of addictive drugs to elicit the release of dopamine in the human striatum. There is robust evidence that stimulants increase striatal dopamine levels and some evidence that alcohol may have such an effect, but little evidence, if any, that cannabis and opiates increase dopamine levels. Moreover, there is good evidence that striatal dopamine receptor availability and dopamine release are diminished in individuals with stimulant or alcohol dependence but not in individuals with opiate, nicotine or cannabis dependence. These observations have implications for understanding reward and treatment responses in various addictions.

Gender differences in the effect of tobacco use on brain phosphocreatine levels in methamphetamine-dependent subjects

BACKGROUND

A high prevalence of tobacco smoking has been observed in methamphetamine users, but there have been no in vivo brain neurochemistry studies addressing gender effects of tobacco smoking in methamphetamine users. Methamphetamine addiction is associated with increased risk of depression and anxiety in females. There is increasing evidence that selective analogues of nicotine, a principal active component of tobacco smoking, may ease depression and improve cognitive performance in animals and humans.

OBJECTIVES

To investigate the effects of tobacco smoking and gender on brain phosphocreatine (PCr) levels, a marker of brain energy metabolism reported to be reduced in methamphetamine-dependent subjects.

METHODS

Thirty female and 27 male methamphetamine-dependent subjects were evaluated with phosphorus-31 magnetic resonance spectroscopy ((31)P-MRS) to measure PCr levels within the pregenual anterior cingulate, which has been implicated in methamphetamine neurotoxicity.

RESULTS

Analysis of covariance revealed that there were statistically significant slope (PCr versus lifetime amount of tobacco smoking) differences between female and male methamphetamine-dependent subjects (p = 0.03). In females, there was also a statistically significant interaction between lifetime amounts of tobacco smoking and methamphetamine in regard to PCr levels (p = 0.01), which suggests that tobacco smoking may have a more significant positive impact on brain PCr levels in heavy, as opposed to light to moderate, methamphetamine-dependent females.

CONCLUSION

These results indicate that tobacco smoking has gender-specific effects in terms of increased anterior cingulate high energy PCr levels in methamphetamine-dependent subjects. Cigarette smoking in methamphetamine-dependent women, particularly those with heavy methamphetamine use, may have a potentially protective effect upon neuronal metabolism.

Monoamine oxidase: radiotracer chemistry and human studies

Monoamine oxidase (MAO) oxidizes amines from both endogenous and exogenous sources thereby regulating the concentration of neurotransmitter amines such as serotonin, norepinephrine, and dopamine as well as many xenobiotics. MAO inhibitor drugs are used in the treatment of Parkinson's disease and in depression stimulating the development of radiotracer tools to probe the role of MAO in normal human biology and in disease. Over the past 30 years since the first radiotracers were developed and the first positron emission tomography (PET) images of MAO in humans were carried out, PET studies of brain MAO in healthy volunteers and in patients have identified different variables that have contributed to different MAO levels in brain and in peripheral organs. MAO radiotracers and PET have also been used to study the current and developing MAO inhibitor drugs including the selection of doses for clinical trials. In this article, we describe the following: (1) the development of MAO radiotracers; (2) human studies including the relationship of brain MAO levels to genotype, personality, neurological, and psychiatric disorders; and (3) examples of the use of MAO radiotracers in drug research and development. We will conclude with outstanding needs to improve the radiotracers that are currently used and possible new applications.

Biomarkers of a five-domain translational substrate for schizophrenia and schizoaffective psychosis

BACKGROUND

The Mental Health Biomarker Project (2010-2014) selected commercial biochemistry markers related to monoamine synthesis and metabolism and measures of visual and auditory processing performance. Within a case-control discovery design with exclusion criteria designed to produce a highly characterised sample, results from 67 independently DSM IV-R-diagnosed cases of schizophrenia and schizoaffective disorder were compared with those from 67 control participants selected from a local hospital, clinic and community catchment area. Participants underwent protocol-based diagnostic-checking, functional-rating, biological sample-collection for thirty candidate markers and sensory-processing assessment.

RESULTS

Fifteen biomarkers were identified on ROC analysis. Using these biomarkers, odds ratios, adjusted for a case-control design, indicated that schizophrenia and schizoaffective disorder were highly associated with dichotic listening disorder, delayed visual processing, low visual span, delayed auditory speed of processing, low reverse digit span as a measure of auditory working memory and elevated levels of catecholamines. Other nutritional and biochemical biomarkers were identified as elevated hydroxyl pyrroline-2-one as a marker of oxidative stress, vitamin D, B6 and folate deficits with elevation of serum B12 and free serum copper to zinc ratio. When individual biomarkers were ranked by odds ratio and correlated with clinical severity, five functional domains of visual processing, auditory processing, oxidative stress, catecholamines and nutritional-biochemical variables were formed. When the strengths of their inter-domain relationships were predicted by Lowess (non-parametric) regression, predominant bidirectional relationships were found between visual processing and catecholamine domains. At a cellular level, the nutritional-biochemical domain exerted a pervasive influence on the auditory domain as well as on all other domains.

CONCLUSIONS

The findings of this biomarker research point towards a much-required advance in Psychiatry: quantification of some theoretically-understandable, translationally-informative, treatment-relevant underpinnings of serious mental illness. This evidence reveals schizophrenia and schizoaffective disorder in a somewhat different manner, as a conglomerate of several disorders many of which are not currently being assessed-for or treated in clinical settings. Currently available remediation techniques for these underlying conditions have potential to reduce treatment-resistance, relapse-prevention, cost burden and social stigma in these conditions. If replicated and validated in prospective trials, such findings will improve progress-monitoring and treatment-response for schizophrenia and schizoaffective disorder.

Behavioral mechanisms underlying nicotine reinforcement

Cigarette smoking is the leading cause of preventable deaths worldwide, and nicotine, the primary psychoactive constituent in tobacco, drives sustained use. The behavioral actions of nicotine are complex and extend well beyond the actions of the drug as a primary reinforcer. Stimuli that are consistently paired with nicotine can, through associative learning, take on reinforcing properties as conditioned stimuli. These conditioned stimuli can then impact the rate and probability of behavior and even function as conditioning reinforcers that maintain behavior in the absence of nicotine. Nicotine can also act as a conditioned stimulus (CS), predicting the delivery of other reinforcers, which may allow nicotine to acquire value as a conditioned reinforcer. These associative effects, establishing non-nicotine stimuli as conditioned stimuli with discriminative stimulus and conditioned reinforcing properties as well as establishing nicotine as a CS, are predicted by basic conditioning principles. However, nicotine can also act non-associatively. Nicotine directly enhances the reinforcing efficacy of other reinforcing stimuli in the environment, an effect that does not require a temporal or predictive relationship between nicotine and either the stimulus or the behavior. Hence, the reinforcing actions of nicotine stem both from the primary reinforcing actions of the drug (and the subsequent associative learning effects) as well as the reinforcement enhancement action of nicotine which is non-associative in nature. Gaining a better understanding of how nicotine impacts behavior will allow for maximally effective tobacco control efforts aimed at reducing the harm associated with tobacco use by reducing and/or treating its addictiveness.

Smoking abstinence and neurocognition: implications for cessation and relapse

In this chapter, we review the last decade of research on the effects of smoking abstinence on various forms of neurocognition, including executive function (working memory, sustained attention, response inhibition), reward processing, and cue-reactivity. In our review we identify smoking abstinence-induced deficits in executive function mediated by effects on frontal circuitry, which in turn is known to be affected by modulation of cholinergic, dopaminergic, and other neurotransmitter systems. We also review evidence that smoking abstinence blunts reactivity to non-drug reinforcers-a finding that is consistent with results in the animal literature. Finally, our review of cue-reactivity indicates that smoking abstinence does not appear to amplify cue-provoked craving, although it may increase attentional bias to smoking-related cues. Inconsistencies across findings and potential contributing factors are discussed. In addition, we review the literature on the effects of nicotine and non-nicotine factors in neurocognition. Finally, we provide a multi-factor model and an agenda for future research on the effects of smoking abstinence on neurocognition. The model includes four distinct yet interacting factors, including: Negative Reinforcement, Drug-Reward Bias, Goal and Skill Interference, and Non-Cognitive Factors. Additional research is needed to further evaluate the scope and time-course of abstinence-induced changes in neurocognition, the mechanisms that underlie these changes and the specific role of these processes in drug reinforcement, lapse, and relapse.

Younger age at onset of sporadic Parkinson's disease among subjects occupationally exposed to metals and pesticides

An earlier age at onset of Parkinson's disease (PD) has been reported to be associated with occupational exposures to manganese and hydrocarbon solvents suggesting that exposure to neurotoxic chemicals may hasten the progression of idiopathic PD. In this study the role of occupational exposure to metals and pesticides in the progression of idiopathic PD was assessed by looking at age at disease onset. The effects of heritable genetic risk factors, which may also influence age at onset, was minimized by including only sporadic cases of PD with no family history of the disease (n=58). Independent samples Student t-test revealed that subjects with occupational exposure to metals and/or pesticides (n=36) were significantly (p=0.013) younger than unexposed controls (n=22). These subjects were then divided into three groups [high (n=18), low (n=18), and unexposed (n=22)] to ascertain if duration of exposure further influenced age at onset of PD. One-way ANOVA revealed that subjects in the high exposure group were significantly (p=0.0121) younger (mean age: 50.33 years) than unexposed subjects (mean age: 60.45 years). Subjects were also stratified by exposure type (metals vs. pesticides). These results suggest that chronic exposure to metals and pesticides is associated with a younger age at onset of PD among patients with no family history of the disease and that duration of exposure is a factor in the magnitude of this effect.

Whole tobacco smoke extracts to model tobacco dependence in animals

Smoking tobacco is highly addictive and a leading preventable cause of death. The main addictive constituent is nicotine; consequently it has been administered to laboratory animals to model tobacco dependence. Despite extensive use, this model might not best reflect the powerful nature of tobacco dependence because nicotine is a weak reinforcer, the pharmacology of smoke is complex and non-pharmacological factors have a critical role. These limitations have led researchers to expose animals to smoke via the inhalative route, or to administer aqueous smoke extracts to produce more representative models. The aim was to review the findings from molecular/behavioural studies comparing the effects of nicotine to tobacco/smoke extracts to determine whether the extracts produce a distinct model. Indeed, nicotine and tobacco extracts yielded differential effects, supporting the initiative to use extracts as a complement to nicotine. Of the behavioural tests, intravenous self-administration experiments most clearly revealed behavioural differences between nicotine and extracts. Thus, future applications for use of this behavioural model were proposed that could offer new insights into tobacco dependence.

Smoking and major depressive disorder in Chinese women

Objective

To investigate the risk factors that contribute to smoking in female patients with major depressive disorder (MDD) and the clinical features in depressed smokers.

Methods

We examined the smoking status and clinical features in 6120 Han Chinese women with MDD (DSM-IV) between 30 and 60 years of age across China. Logistic regression was used to determine the association between clinical features of MDD and smoking status and between risk factors for MDD and smoking status.

Results

Among the recurrent MDD patients there were 216(3.6%) current smokers, 117 (2.0%) former smokers and 333(5.6%) lifetime smokers. Lifetime smokers had a slightly more severe illness, characterized by more episodes, longer duration, more comorbid illness (panic and phobias), with more DSM-IV A criteria and reported more symptoms of fatigue and suicidal ideation or attempts than never smokers. Some known risk factors for MDD were also differentially represented among smokers compared to non-smokers. Smokers reported more stressful life events, were more likely to report childhood sexual abuse, had higher levels of neuroticism and an increased rate of familial MDD. Only neuroticism was significantly related to nicotine dependence.

Conclusions

Although depressed women smokers experience more severe illness, smoking rates remain low in MDD patients. Family history of MDD and environmental factors contribute to lifetime smoking in Chinese women, consistent with the hypothesis that the association of smoking and depression may be caused by common underlying factors.

Dopamine function in cigarette smokers: an [¹⁸F]-DOPA PET study

Tobacco addiction is a global public health problem. Addiction to tobacco is thought to involve the effects of nicotine on the dopaminergic system. Only one study has previously investigated dopamine synthesis capacity in cigarette smokers. This study, exclusively in male volunteers, reported increased dopamine synthesis capacity in heavy smokers compared with non-smokers. We sought to determine whether dopamine synthesis capacity was elevated in a larger sample of cigarette smokers that included females. Dopamine synthesis capacity was measured in 15 daily moderate smokers with 15 sex- and age-matched control subjects who had never smoked tobacco. Dopamine synthesis capacity (indexed as the influx rate constant K(i)(cer)) was measured with positron emission tomography and 3,4-dihydroxy-6-[(18)F]-fluoro-l-phenylalanine. There was no significant group difference in dopamine synthesis capacity between smokers and non-smoker controls in the whole striatum (t28=0.64, p=0.53) or any of its functional subdivisions. In smokers, there were no significant relationships between the number of cigarettes smoked per day and dopamine synthesis capacity in the whole striatum (r=-0.23, p=0.41) or any striatal subdivision. These findings indicate that moderate smoking is not associated with altered striatal dopamine synthesis capacity.

Prenatal drug exposure, behavioral problems, and drug experimentation among African-American urban adolescents

PURPOSE

To examine how prenatal drug exposure (PDE) to heroin/cocaine and behavioral problems relate to adolescent drug experimentation.

METHODS

The sample included African-American adolescents (mean age = 14.2 years, SD = 1.2) with PDE (n = 73) and a nonexposed community comparison (n = 61). PDE status was determined at delivery through toxicology analysis and maternal report. Internalizing/externalizing problems were assessed during adolescence with the Behavior Assessment System for Children, Second Edition. Drug experimentation was assessed by adolescent report and urine analysis. Logistic regression evaluated the likelihood of drug experimentation related to PDE and behavioral problems, adjusting for age, gender, PDE, perceived peer drug use, and caregiver drug use. Interaction terms examined gender modification.

RESULTS

Sixty-seven subjects (50%) used drugs: 25 (19%) used tobacco/alcohol only and 42 (31%) used marijuana/illegal drugs. Ninety-four subjects (70%) perceived peer drug use. PDE significantly increased the risk of tobacco/alcohol experimentation (odds ratio = 3.07, 95% confidence interval [CI] 1.09-8.66, p = .034) but not after covariate adjustment (adjusted odds ratio [aOR] = 1.16, 95% CI .31-4.33, p > .05). PDE was not related to the overall or marijuana/illegal drug experimentation. The likelihood of overall drug experimentation was doubled per SD increase in externalizing problems (aOR = 2.28, 95% CI 1.33-3.91, p = .003) and, among girls, 2.82 times greater (aOR = 2.82, 95% CI 1.34-5.94, p = .006) per SD increase in internalizing problems. Age and perceived peer drug use were significant covariates.

CONCLUSIONS

Drug experimentation was relatively common (50%), especially in the context of externalizing problems, internalizing problems (girls only), older age, and perceived peer drug use. Findings support the Problem Behavior Theory and suggest that adolescent drug prevention addresses behavioral problems and promotes prosocial peer groups.

Neuroleptics and enrichment environment treatment in memory disorders and other central nervous system function observed in prenatally stressed rats

It is believed that the most effective method of treatment in schizophrenia is pharmacotherapy, in particular, the use of atypical neuroleptics like aripiprazole (ARI) and olanzapine (OLA). Moreover, studies of many authors have shown that enriched living conditions and tobacco smoke exposure can also affect the cognitive functions that are disturbed in the course of schizophrenia. The aim of the study was to find whether tobacco smoke and enrichment living conditions have the influence on cognitive functions in the newborn offspring of prenatally stressed rats and whether drugs such as ARI (1.5 mg/kg intraperitoneally (i.p.)) and OLA (0.5 mg/kg ip) in single and chronic treatment modify those functions (Morris water maze). The study (in the same conditions) also analyses immobility time (Porsolt test) and motor activity of animals that received ARI and OLA. It has been shown that ARI and OLA as well as enriched environment reduce cognitive function disorders and modify cognitive functions in rats exposed to tobacco smoke. In turn, current research has shown that nicotine has increased cognitive function disorders compared to the previous study (animals without tobacco smoke exposure).

Effects of smoking on D₂/D₃ striatal receptor availability in alcoholics and social drinkers

Studies have reported lower striatal D₂/D₃ receptor availability in both alcoholics and cigarette smokers relative to healthy controls. These substances are commonly co-abused, yet the relationship between comorbid alcohol/tobacco abuse and striatal D₂/D₃ receptor availability has not been examined. We sought to determine the degree to which dual abuse of alcohol and tobacco is associated with lower D₂/D₃ receptor availability. Eighty-one subjects (34 nontreatment-seeking alcoholic smokers [NTS-S], 21 social-drinking smokers [SD-S], and 26 social-drinking non-smokers [SD-NS]) received baseline [(11)C]raclopride scans. D₂/D₃ binding potential (BPND ≡ Bavail/KD) was estimated for ten anatomically defined striatal regions of interest (ROIs). Significant group effects were detected in bilateral pre-commissural dorsal putamen, bilateral pre-commissural dorsal caudate; and bilateral post-commissural dorsal putamen. Post-hoc testing revealed that, regardless of drinking status, smokers had lower D₂/D₃ receptor availability than non-smoking controls. Chronic tobacco smokers have lower striatal D₂/D₃ receptor availability than non-smokers, independent of alcohol use. Additional studies are needed to identify the mechanisms by which chronic tobacco smoking is associated with striatal dopamine receptor availability.

Comparison of the reinforcing properties of nicotine and cigarette smoke extract in rats

Tobacco dependence is difficult to treat, with the vast majority of those who try to quit relapsing within the first year. Improvements in smoking cessation therapies may be achieved by improving current preclinical research methods. However, most experimental tests in animals use nicotine alone, ignoring the 8000 other constituents found in tobacco smoke. To improve on this model, we have used self-administration to test the reinforcing properties of aqueous cigarette smoke extract (CSE) in rats, made by bubbling cigarette smoke through a saline solution. CSE is more potent than nicotine alone in both the acquisition and maintenance of self-administration, but did not exhibit higher progressive ratio responding. Mecamylamine and varenicline had similar potencies to block nicotine and CSE self-administration, indicating the involvement of nicotinic receptors in CSE reinforcement. Following extinction of responding, reinstatement was triggered by exposing animals to a pharmacological stressor, yohimbine (2.5 mg/kg, i.p.), alone and in combination with cues. Animals that self-administered CSE were significantly more sensitive to stress-induced reinstatement than those that self-administered nicotine. Ligand binding autoradiography studies showed nicotine and CSE to have similar affinities for different nicotinic receptor types. CSE significantly reduced MAO-A and MAO-B activities in vitro, whereas nicotine did not. Although CSE inhibition of MAO-A activity in vitro was found to be partially irreversible, irreversible inhibition was not observed in vivo. These experiments show that CSE is an effective reinforcer acting via nicotinic receptors. Furthermore, it better models MAO inhibition and is more sensitive to stress-induced reinstatement than nicotine alone, which is a potent trigger for relapse in smokers.

Long-term effects of adolescent smoking on depression and socioeconomic status in adulthood in an urban African American cohort

Despite known adverse causal effects of cigarette smoking on mental health, findings for the effects of adolescent cigarette smoking on later depression and socioeconomic status remain inconclusive. Previous studies have had shorter follow-up periods and did not have a representative portion of the African American population. Using an analytical method that matches adolescent smokers with nonsmokers on childhood and background variables, this study aims to provide evidence on the effects of adolescent regular smoking on adult depression and socioeconomic status. Our longitudinal study is from the Woodlawn Study that followed 1,242 African Americans in Chicago from 1966-1967 (at age 6-7) through 2002-2003 (at age 42-43). We used a propensity score matching method to find a regular and a non-regular adolescent smoking group with similar childhood socioeconomic and family background and first grade academic and behavioral performance. We compared the matched samples to assess the longitudinal effects of adolescent smoking on adult outcomes. Comparing the matched 199 adolescent regular smokers and 199 non-regular smokers, we found statistical support for the effects of adolescent cigarette smoking on later educational attainment (OR, 2.13; 95 % CI, 1.34, 3.39) and long-term unemployment (OR, 1.74; 95 % CI, 1.11, 2.75), but did not find support for the effects on adulthood major depressive disorders. With a community population of urban African Americans followed for 40 years, our study contributes to the understanding of the relationships between adolescent smoking and later educational attainment and employment.

Kinetic modeling of the monoamine oxidase B radioligand [¹¹C]SL25.1188 in human brain with high-resolution positron emission tomography

This article describes the kinetic modeling of [(11)C]SL25.1188 ([(S)-5-methoxymethyl-3-[6-(4,4,4-trifluorobutoxy)-benzo[d]isoxazol-3-yl]-oxazolidin-2-[(11)C]one]) binding to monoamine oxidase B (MAO-B) in the human brain using high-resolution positron emission tomography (PET). Seven healthy subjects underwent two separate 90- minute PET scans after an intravenous injection of [(11)C]SL25.1188. Complementary arterial blood sampling was acquired. Radioactivity was quickly eliminated from plasma with 80% of parent compound remaining at 90 minutes. Metabolites were more polar than the parent compound. Time-activity curves showed high brain uptake, early peak and washout rate consistent with known regional MAO-B concentration. A two-tissue compartment model (2-TCM) provided better fits to the data than a 1-TCM. Measurement of total distribution volume (VT) showed very good identifiability (based on coefficient of variation (COV)) for all regions of interest (ROIs) (COV(VT)<8%), low between-subject variability (∼20%), and quick temporal convergence (within 5% of final value at 45 minutes). Logan graphical method produces very good estimation of VT. Regional VT highly correlated with previous postmortem report of MAO-B level (r(2)= ≥ 0.9). Specific binding would account from 70% to 90% of VT. Hence, VT measurement of [(11)C]SL25.1(1)88 PET is an excellent estimation of MAO-B concentration.

Untargeted metabolomic profiling in saliva of smokers and nonsmokers by a validated GC-TOF-MS method

A GC-TOF-MS method was developed and validated for a metabolic fingerprinting in saliva of smokers and nonsmokers. We validated the method by spiking 37 different metabolites and 6 internal standards to saliva between 0.1 μM and 2 mM. Intraday coefficients of variation (CVs) (accuracies) were on average, 11.9% (85.8%), 8.2% (88.9%), and 10.0% (106.7%) for the spiked levels 25, 50, and 200 μM, respectively (N = 5). Interday CVs (accuracies) were 12.4% (97%), 18.8% (95.5%), and 17.2% (105.9%) for the respective levels of 25, 50, and 200 μM (N = 5). The method was applied to saliva of smokers and nonsmokers, obtained from a 24 h diet-controlled clinical study, in order to identify biomarkers of endogenous origin, which could be linked to smoking related diseases. Automated peak picking, integration, and statistical analysis were conducted by the software tools MZmine, Metaboanalyst, and PSPP. We could identify 13 significantly altered metabolites in smokers (p < 0.05) by matching them against MS libraries and authentic standard compounds. Most of the identified metabolites, including tyramine, adenosine, and glucose-6-phosphate, could be linked to smoking-related perturbations and may be associated with established detrimental effects of smoking.

Changes in prevalence of depression and anxiety following smoking cessation: results from an international cohort study (ATTEMPT)

BACKGROUND

Smoking cessation improves physical health but it has been suggested that in vulnerable individuals it may worsen mental health. This study aimed to identify the short- and longer-term effects of stopping smoking on depression and anxiety in the general population and in those with a history of these disorders.

METHOD

Sociodemographic and smoking characteristics, and mental and physical health were assessed using established measures in the ATTEMPT cohort, an international longitudinal study of smokers (n = 3645). Smokers who had stopped for at least 3 months or less than 3 months at the 12-month follow-up were compared with current smokers (n = 1640).

RESULTS

At follow-up, 9.7% [95% confidence interval (CI) 8.3-11.2] of smokers had stopped for less than 3 months and 7.5% (95% CI 6.3-8.9) for at least 3 months. Compared with current smokers, prevalence of depression prescriptions obtained in the last 2 weeks was lower for those who had stopped for less than 3 months [odds ratio (OR) 0.37, 95% CI 0.14-0.96] or at least 3 months (OR 0.25, 95% CI 0.06-0.94) after adjusting for baseline prescription levels and confounding variables. Adjusted prevalence of recent depression symptoms was also lower for ex-smokers who had stopped for less than 3 months (OR 0.34, 95% CI 0.15-0.78) or at least 3 months (OR 0.24, 95% CI 0.09-0.67) than among continuing smokers. There was no change in anxiety measures in the general population or any increase in anxiety or depression symptoms in ex-smokers with a past history of these conditions.

CONCLUSIONS

Smoking cessation does not appear to be associated with an increase in anxiety or depression and may lead to a reduced incidence of depression.