The role of dopamine in reward and pleasure behaviour--review of data from preclinical research

The mesopontine tegmentum in reward and aversion: From cellular heterogeneity to behaviour

The mesopontine tegmentum, comprising the pedunculopontine tegmentum (PPN) and the laterodorsal tegmentum (LDT), is intricately connected to various regions of the basal ganglia, motor systems, and limbic systems. The PPN and LDT can regulate the activity of different brain regions of these target systems, and in this way are in a privileged position to modulate motivated behaviours. Despite recent findings, the PPN and LDT have been largely overlooked in discussions about the neural circuits associated with reward and aversion. This review aims to provide a timely and comprehensive resource on past and current research, highlighting the PPN and LDT's connectivity and influence on basal ganglia and limbic, and motor systems. Seminal studies, including lesion, pharmacological, and optogenetic/chemogenetic approaches, demonstrate their critical roles in modulating reward/aversive behaviours. The review emphasizes the need for further investigation into the associated cellular mechanisms, in order to clarify their role in behaviour and contribution for different neuropsychiatric disorders.

Focused Ultrasound Modulates Dopamine in a Mesolimbic Reward Circuit

Dopamine is a neurotransmitter that plays a significant role in reward and motivation. Dysfunction in the mesolimbic dopamine pathway has been linked to a variety of psychiatric disorders, including addiction. Low-intensity focused ultrasound (LIFU) has demonstrated effects on brain activity, but how LIFU affects dopamine neurotransmission is not known. Here, we applied three different intensities (6.5, 13, and 26 W/cm 2 I sppa ) of 2-minute LIFU to the prelimbic region (PLC) and measured dopamine in the nucleus accumbens (NAc) core using fast-scan cyclic voltammetry. Two minutes of LIFU sonication at 13 W/cm 2 to the PLC significantly reduced dopamine release by ∼ 50% for up to 2 hours. However, double the intensity (26 W/cm 2 ) resulted in less inhibition (∼30%), and half the intensity (6.5 W/cm 2 ) did not result in any inhibition of dopamine. Anatomical controls applying LIFU to the primary somatosensory cortex did not change NAc core dopamine, and applying LIFU to the PLC did not affect dopamine release in the caudate or NAc shell. Histological evaluations showed no evidence of cell damage or death. Modeling of temperature rise demonstrates a maximum temperature change of 0.5°C with 13 W/cm 2 , suggesting that modulation is not due to thermal mechanisms. These studies show that LIFU at a moderate intensity provides a noninvasive, high spatial resolution means to modulate specific mesolimbic circuits that could be used in future studies to target and repair pathways that are dysfunctional in addiction and other psychiatric diseases.

The emerging neuroimmune hypothesis of bipolar disorder: An updated overview of neuroimmune and microglial findings

Bipolar disorder (BD) is a severe and multifactorial disease, with onset usually in young adulthood, which follows a progressive course throughout life. Replicated epidemiological studies have suggested inflammatory mechanisms and neuroimmune risk factors as primary contributors to the onset and development of BD. While not all patients display overt markers of inflammation, significant evidence suggests that aberrant immune signaling contributes to all stages of the disease and seems to be mood phase dependent, likely explaining the heterogeneity of findings observed in this population. As the brain's immune cells, microglia orchestrate the brain's immune response and play a critical role in maintaining the brain's health across the lifespan. Microglia are also highly sensitive to environmental changes and respond to physiological and pathological events by adapting their functions, structure, and molecular expression. Recently, it has been highlighted that instead of a single population of cells, microglia comprise a heterogeneous community with specialized states adjusted according to the local molecular cues and intercellular interactions. Early evidence has highlighted the contribution of microglia to BD neuropathology, notably for severe outcomes, such as suicidality. However, the roles and diversity of microglial states in this disease are still largely undermined. This review brings an updated overview of current literature on the contribution of neuroimmune risk factors for the onset and progression of BD, the most prominent neuroimmune abnormalities (including biomarker, neuroimaging, ex vivo studies) and the most recent findings of microglial involvement in BD neuropathology. Combining these different shreds of evidence, we aim to propose a unifying hypothesis for BD pathophysiology centered on neuroimmune abnormalities and microglia. Also, we highlight the urgent need to apply novel multi-system biology approaches to characterize the diversity of microglial states and functions involved in this enigmatic disorder, which can open bright perspectives for novel biomarkers and therapeutic discoveries.

Co-targeting the kappa opioid receptor and dopamine transporter reduces motivation to self-administer cocaine and partially reverses dopamine system dysregulation

Cocaine disrupts dopamine (DA) and kappa opioid receptor (KOR) system activity, with long-term exposure reducing inhibiton of DA uptake by cocaine and increasing KOR system function. Single treatment therapies have not been successful for cocaine use disorder; therefore, this study focuses on a combination therapy targeting the dopamine transporter (DAT) and KOR. Sprague Dawley rats self-administered 5 days of cocaine (1.5 mg/kg/inf, max 40 inf/day, FR1), followed by 14 days on a progressive ratio (PR) schedule (0.19 mg/kg/infusion). Behavioral effects of individual and combined administration of phenmetrazine and nBNI were then examined using PR. Additionally, ex vivo fast scan cyclic voltammetry was then used to assess alterations in DA and KOR system activity in the nucleus accumbens before and after treatments. Chronic administration of phenmetrazine as well as the combination of phenmetrazine and nBNI-but not nBNI alone-significantly reduced PR breakpoints. In addition, the combination of phenmetrazine and nBNI partially reversed cocaine-induced neurodysregulations of the KOR and DA systems, indicating therapeutic benefits of targeting the DA and KOR systems in tandem. These data highlight the potential benefits of the DAT and KOR as dual-cellular targets to reduce motivation to administer cocaine and reverse cocaine-induced alterations of the DA system.

Alterations in type 2 dopamine receptors across neuropsychiatric conditions: A large-scale PET cohort

PURPOSE

Aberrant dopaminergic function is linked with motor, psychotic, and affective symptoms, but studies have typically compared a single patient group with healthy controls.

METHODS

Here, we investigated the variation in striatal (caudate nucleus, nucleus accumbens, and putamen) and thalamic type 2 dopamine receptor (D2R) availability using [11C]raclopride positron emission tomography (PET) data from a large sample of 437 humans including healthy controls, and subjects with Parkinson's disease (PD), antipsychotic-naïve schizophrenia, severe violent behavior, pathological gambling, depression, and overweight. We analyzed regional group differences in D2R availability. We also analyzed the interregional correlation in D2R availability within each group.

RESULTS

Subjects with PD showed the clearest decline in D2R availability. Overall, the groups showed high interregional correlation in D2R availability, while this pattern was weaker in violent offenders. Subjects with schizophrenia, pathological gambling, depression, or overweight did not show clear changes in either the regional receptor availability or the interregional correlation.

CONCLUSION

We conclude that the dopaminergic changes in neuropsychiatric conditions might not only affect the overall receptor availability but also how coupled regions are across people. The region-specific receptor availability more profoundly links to the motor symptoms, while the between-region coupling might be disrupted in violence.

Lack of effect of methamphetamine on reward-related brain activity in healthy adults

INTRODUCTION

Stimulant drugs are thought to alter processing of rewarding stimuli. However, the mechanisms by which they do this are not fully understood.

METHOD

In this study we used EEG to assess effects of single doses of methamphetamine (MA) on neural responses during anticipation and receipt of reward in healthy volunteers. Healthy young men and women (N = 28) completed three sessions in which they received placebo, a low MA dose (10 mg) or a higher MA dose (20 mg) under double blind conditions. Subjective and cardiovascular measures were obtained, and EEG was used to assess brain activity during an electrophysiological version of the Monetary Incentive Delay (eMID) task.

RESULTS

EEG measures showed expected patterns during anticipation and receipt of reward, and MA produced its expected effects on mood and cardiovascular function. However, MA did not affect EEG responses during either anticipation or receipt of rewards.

CONCLUSIONS

These findings suggest that the effects of MA on EEG signals of reward processing are subtle, and not related to the drug's effects on subjective feelings of well-being. The findings contribute to our understanding of the neural effects of MA during behaviors related to reward.

Dopaminergic and norepinephrinergic modulation of endogenous event-related potentials: A systematic review and meta-analysis

Event-related potentials (ERPs) represent the cortical processing of sensory, motor or cognitive functions invoked by particular events or stimuli. A current theory posits that the catecholaminergic neurotransmitters dopamine (DA) and norepinephrine (NE) modulate a number of endogenous ERPs during various cognitive processes. This manuscript aims to evaluate a leading neurotransmitter hypothesis with a systematic overview and meta-analysis of pharmacologic DA and NE manipulation of specific ERPs in healthy subjects during executive function. Specifically, the frontally-distributed P3a, N2, and Ne/ERN (or error-related negativity) are supposedly modulated primarily by DA, whereas the parietally-distributed P3b is thought to be modulated by NE. Based on preceding research, we refer to this distinction between frontally-distributed DA-sensitive and parietally-distributed NE-sensitive ERP components as the Extended Neurobiological Polich (ENP) hypothesis. Our systematic review and meta-analysis indicate that this distinction is too simplistic and many factors interact with DA and NE to influence these specific ERPs. These may include genetic factors, the specific cognitive processes engaged, or elements of study design, i.e. session or sequence effects or data-analysis strategies.

Does partial blockade of dopamine D2 receptors with Amisulpride cause anhedonia? An experimental study in healthy volunteers

BACKGROUND

Anhedonia is a frequent cause of functional im^pairment in psychosis. Although it is plausible that medication-induced D2 receptor blockade could diminish hedonic responding, there is little experimental research testing this hypothesis in humans.

METHODS

To inspect possible effects of partial D2 blockade on hedonic experiences, we administered 300 mg of Amisulpride or placebo to 85 participants in a randomized, double-blind, placebo-controlled trial. Participants were then subjected to an emotional evocation task utilizing standardized pictorial pleasant, neutral, and unpleasant stimuli.

RESULTS

We observed lower positivity ratings in the Amisulpride group compared to placebo across all stimulus categories (p = .026, f = 0.25) and no group differences in negativity or arousal ratings. The Amisulpride group also showed lower electrodermal responses across all stimulus categories compared to placebo (p = .017, f = 0.27). The electrodermal response was especially diminished for pleasant stimuli.

CONCLUSION

We interpret our findings as evidence that D2 blockade via Amisulpride can reduce at-the-moment hedonic responsivity in healthy volunteers. If these results can be confirmed in drug-naïve clinical samples, this would indicate that antipsychotic medication contributes to clinical anhedonia, probably via antagonistic effects at the dopamine D2 receptor.

Current Perspectives on Selective Dopamine D3 Receptor Antagonists/Partial Agonists as Pharmacotherapeutics for Opioid and Psychostimulant Use Disorders

Over three decades of evidence indicate that dopamine (DA) D3 receptors (D3R) are involved in the control of drug-seeking behavior and may play an important role in the pathophysiology of substance use disorders (SUD). The expectation that a selective D3R antagonist/partial agonist would be efficacious for the treatment of SUD is based on the following key observations. First, D3R are distributed in strategic areas belonging to the mesolimbic DA system such as the ventral striatum, midbrain, and ventral pallidum, which have been associated with behaviors controlled by the presentation of drug-associated cues. Second, repeated exposure to drugs of abuse produces neuroadaptations in the D3R system. Third, the synthesis and characterization of highly potent and selective D3R antagonists/partial agonists have further strengthened the role of the D3R in SUD. Based on extensive preclinical and preliminary clinical evidence, the D3R shows promise as a target for the development of pharmacotherapies for SUD as reflected by their potential to (1) regulate the motivation to self-administer drugs and (2) disrupt the responsiveness to drug-associated stimuli that play a key role in reinstatement of drug-seeking behavior triggered by re-exposure to the drug itself, drug-associated environmental cues, or stress. The availability of PET ligands to assess clinically relevant receptor occupancy by selective D3R antagonists/partial agonists, the definition of reliable dosing, and the prospect of using human laboratory models may further guide the design of clinical proof of concept studies. Pivotal clinical trials for more rapid progression of this target toward regulatory approval are urgently required. Finally, the discovery that highly selective D3R antagonists, such as R-VK4-116 and R-VK4-40, do not adversely affect peripheral biometrics or cardiovascular effects alone or in the presence of oxycodone or cocaine suggests that this class of drugs has great potential in safely treating psychostimulant and/or opioid use disorders.

Pregestational Exposure to T. gondii Produces Maternal Antibodies That Recognize Fetal Brain Mimotopes and Induces Neurochemical and Behavioral Dysfunction in the Offspring

The activation of the maternal immune system by a prenatal infection is considered a risk factor for developing psychiatric disorders in the offspring. Toxoplasma gondii is one of the pathogenic infections associated with schizophrenia. Recent studies have shown an association between high levels of IgG anti-T. gondii from mothers and their neonates, with a higher risk of developing schizophrenia. The absence of the parasite and the levels of IgGs found in the early stages of life suggest a transplacental transfer of the anti-T. gondii IgG antibodies, which could bind fetal brain structures by molecular mimicry and induce alterations in neurodevelopment. This study aimed to determine the maternal pathogenic antibodies formation that led to behavioral impairment on the progeny of rats immunized with T. gondii. Female rats were immunized prior to gestation with T. gondii lysate (3 times/once per week). The anti-T. gondii IgG levels were determined in the serum of pregestational exposed females' previous mating. After this, locomotor activity, cognitive and social tests were performed. Cortical neurotransmitter levels for dopamine and glutamate were evaluated at 60 PND in the progeny of rats immunized before gestation (Pregestational group). The maternal pathogenic antibodies were evidenced by their binding to fetal brain mimotopes in the Pregestational group and the reactivity of the serum containing anti-T. gondii IgG was tested in control fetal brains (non-immunized). These results showed that the Pregestational group presented impairment in short and long-term memory, hypoactivity and alteration in social behavior, which was also associated with a decrease in cortical glutamate and dopamine levels. We also found the IgG antibodies bound to brain mimotopes in fetuses from females immunized with T. gondii, as well as observing a strong reactivity of the serum females immunized for fetal brain structures of fetuses from unimmunized mothers. Our results suggest that the exposure to T. gondii before gestation produced maternal pathogenic antibodies that can recognize fetal brain mimotopes and lead to neurochemical and behavioral alterations in the offspring.

Second-Derivative-Based Background Drift Removal for a Tonic Dopamine Measurement in Fast-Scan Cyclic Voltammetry

The dysregulation of dopamine, a neuromodulator, is associated with a broad spectrum of brain disorders, including Parkinson's disease, addiction, and schizophrenia. Quantitative measurements of dopamine are essential for understanding dopamine functional dynamics. Fast-scan cyclic voltammetry (FSCV) is the most popular electrochemical technique for measuring real-time in vivo dopamine level changes. Standard FSCV has only analyzed "phasic dopamine" (changes in seconds) because the gradual generation of background charging current is inevitable and is the primary noise source in the low-frequency band. Although "tonic dopamine" (changes in minutes to hours) is critical for understanding the dopamine system, an electrochemical technique capable of simultaneously measuring phasic and tonic dopamine in an in vivo environment has not been established. Several modified voltammetric techniques have been developed for measuring tonic dopamine; however, the sampling rates (0.1-0.05 Hz) are too low to be useful. Further investigation of the in vivo applicability of previously developed background drift removal methods for measuring tonic dopamine levels is required. We developed a second-derivative-based background removal (SDBR) method for simultaneously measuring phasic and tonic neurotransmitter levels in real-time. The performance of this technique was tested via in silico and in vitro tonic dopamine experiments. Furthermore, its applicability was tested in vivo. SDBR is a simple, robust, postprocessing technique that can extract tonic neurotransmitter levels from all FSCV data. As SDBR is calculated in individual-scan voltammogram units, it can be applied to any real-time closed-loop system that uses a neurotransmitter as a biomarker.

Neural substrates of motivational dysfunction across neuropsychiatric conditions: Evidence from meta-analysis and lesion network mapping

Motivational dysfunction constitutes one of the fundamental dimensions of psychopathology cutting across traditional diagnostic boundaries. However, it is unclear whether there is a common neural circuit responsible for motivational dysfunction across neuropsychiatric conditions. To address this issue, the current study combined a meta-analysis on psychiatric neuroimaging studies of reward/loss anticipation and consumption (4308 foci, 438 contrasts, 129 publications) with a lesion network mapping approach (105 lesion cases). Our meta-analysis identified transdiagnostic hypoactivation in the ventral striatum (VS) for clinical/at-risk conditions compared to controls during the anticipation of both reward and loss. Moreover, the VS subserves a key node in a distributed brain network which encompasses heterogeneous lesion locations causing motivation-related symptoms. These findings do not only provide the first meta-analytic evidence of shared neural alternations linked to anticipatory motivation-related deficits, but also shed novel light on the role of VS dysfunction in motivational impairments in terms of both network integration and psychological functions. Particularly, the current findings suggest that motivational dysfunction across neuropsychiatric conditions is rooted in disruptions of a common brain network anchored in the VS, which contributes to motivational salience processing rather than encoding positive incentive values.

The effect of β-caryophyllene on food addiction and its related behaviors: A randomized, double-blind, placebo-controlled trial

Food addiction (FA) is a psychological construct that may be involved in the etiology of obesity. The cannabinoid system is involved in the addictive-like food preferences by acting on the dopaminergic pathway of the brain. β-caryophyllene is a dietary cannabinoid that is a cannabinoid type 2 (CB2) receptor agonist. This study explored the impacts of β-caryophyllene supplementation on eating behavior, appetite, mental health, anthropometric parameters, body composition, and some hormones related to appetite in women with obesity diagnosed with FA. Women with obesity and FA, diagnosed by the Yale Food Addiction Scale Score (YFAS-S) ≥3, were randomly allocated to receive a β-caryophyllene softgel (n = 26) (100 mg/daily with meal) or placebo (n = 26) for 8 weeks. Anthropometric measurements, body composition, eating behavior, biochemical markers, dietary intake, appetite, stress, anxiety, and depression were evaluated during the study period. β-caryophyllene administration significantly reduced YFAS-S compared to the placebo group (changes in FA score: 1.5 ± 0.9 vs. - 0.7 ± 1.4; corrected P = 0.05). Serum levels of orexin-A significantly decreased in the β-caryophyllene group (p = 0.02); however, no significant difference was observed compared to the placebo group (corrected P = 0.09). β-caryophyllene supplementation had no significant effect on body composition, anthropometric indices, appetite, eating behavior, dietary intake, physical activity level, mental health, and levels of oxytocin and neuropeptide Y (NPY), compared to the placebo. β-caryophyllene supplementation may have beneficial effects on improving YFAS-S in women with obesity diagnosed with FA. TRIAL REGISTRATION: Iranian Registry of Clinical Trials identifier: IRCT20200914048712N1.

The human physiology of well-being: A systematic review on the association between neurotransmitters, hormones, inflammatory markers, the microbiome and well-being

To understand the pathways through which well-being contributes to health, we performed a systematic review according to the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) guidelines on the association between well-being and physiological markers in four categories, neurotransmitters, hormones, inflammatory markers, and microbiome. We identified 91 studies. Neurotransmitter studies (k_{number of studies}=9) reported only a possible positive association between serotonin and well-being. For the hormone studies (k = 48), a lower momentary cortisol level was related to higher well-being (meta-analytic r = -0.06), and a steeper diurnal slope of cortisol levels. Inflammatory marker studies (k = 36) reported negative or non-significant relations with well-being, with meta-analytic estimates of respectively r = -0.07 and r = -0.05 for C-reactive protein and interleukin-6. Microbiome studies (k = 4) reported inconsistent associations between different bacteria abundance and well-being. The results indicate possible but small roles of serotonin, cortisol, and inflammatory markers in explaining differences in well-being. The inconsistent and limited results for other markers and microbiome require further research. Future directions for a complete picture of the physiological factors underlying well-being are proposed.

Dysfunctional Heteroreceptor Complexes as Novel Targets for the Treatment of Major Depressive and Anxiety Disorders

Among mental diseases, major depressive disorder (MDD) and anxiety deserve a special place due to their high prevalence and their negative impact both on society and patients suffering from these disorders. Consequently, the development of novel strategies designed to treat them quickly and efficiently, without or at least having limited side effects, is considered a highly important goal. Growing evidence indicates that emerging properties are developed on recognition, trafficking, and signaling of G-protein coupled receptors (GPCRs) upon their heteromerization with other types of GPCRs, receptor tyrosine kinases, and ionotropic receptors such as N-methyl-D-aspartate (NMDA) receptors. Therefore, to develop new treatments for MDD and anxiety, it will be important to identify the most vulnerable heteroreceptor complexes involved in MDD and anxiety. This review focuses on how GPCRs, especially serotonin, dopamine, galanin, and opioid heteroreceptor complexes, modulate synaptic and volume transmission in the limbic networks of the brain. We attempt to provide information showing how these emerging concepts can contribute to finding new ways to treat both MDD and anxiety disorders.

Reward Deficiency Syndrome (RDS) Surprisingly Is Evolutionary and Found Everywhere: Is It "Blowin' in the Wind"?

Reward Deficiency Syndrome (RDS) encompasses many mental health disorders, including a wide range of addictions and compulsive and impulsive behaviors. Described as an octopus of behavioral dysfunction, RDS refers to abnormal behavior caused by a breakdown of the cascade of reward in neurotransmission due to genetic and epigenetic influences. The resultant reward neurotransmission deficiencies interfere with the pleasure derived from satisfying powerful human physiological drives. Epigenetic repair may be possible with precision gene-guided therapy using formulations of KB220, a nutraceutical that has demonstrated pro-dopamine regulatory function in animal and human neuroimaging and clinical trials. Recently, large GWAS studies have revealed a significant dopaminergic gene risk polymorphic allele overlap between depressed and schizophrenic cohorts. A large volume of literature has also identified ADHD, PTSD, and spectrum disorders as having the known neurogenetic and psychological underpinnings of RDS. The hypothesis is that the true phenotype is RDS, and behavioral disorders are endophenotypes. Is it logical to wonder if RDS exists everywhere? Although complex, “the answer is blowin’ in the wind,” and rather than intangible, RDS may be foundational in species evolution and survival, with an array of many neurotransmitters and polymorphic loci influencing behavioral functionality.

Association of Acute Postoperative Pain and Cigarette Smoking With Cerebrospinal Fluid Levels of Beta-Endorphin and Substance P

Objectives: Cigarette smoking is associated with postoperative pain perception, which might be mediated by beta-endorphin and substance P. These effects on postoperative pain perception have never been investigated in human cerebrospinal fluid (CSF), which reflects biochemical alterations in the brain. Therefore, we investigated the associations among cigarette smoking, postoperative pain, and levels of beta-endorphin and substance P in human CSF.

Methods: We recruited 160 Chinese men (80 active smokers and 80 nonsmokers) who underwent lumbar puncture before anterior cruciate ligament reconstruction, and 5-ml CSF samples were collected. Pain visual analog scale (VAS) scores, post-anesthetic recovery duration (PARD), and smoking variables were obtained. CSF levels of beta-endorphin and substance P were measured.

Results: Compared to non-smokers, active smokers had significantly higher pain VAS (2.40 ± 0.67 vs. 1.70 ± 0.86, p < 0.001) and PARD scores (9.13 ± 2.11 vs. 7.27 ± 1.35, p = 0.001), lower CSF beta-endorphin (33.76 ± 1.77 vs. 35.66 ± 2.20, p = 0.001) and higher CSF substance P (2,124.46 ± 217.34 vs. 1,817.65 ± 302.14, p < 0.001) levels. Pain VAS scores correlated with PARD in active smokers (r = 0.443, p = 0.001).

Conclusions: Cigarette smoking is associated with increased postoperative pain intensity, shown by delayed pain perception, higher pain VAS scores, and lower beta-endorphin and higher substance P levels in the CSF of active smokers. The more extended postoperative pain perception is delayed, the more pain intensity increases.

Influence of Nicotine from Diverse Delivery Tools on the Autonomic Nervous and Hormonal Systems

Background: Through measurements of the heart rate variability (HRV) accompanied by the pertinent biomarker assays, the effects of nicotine and byproducts derived from alternative nicotine delivery systems (ANDS) on the autonomic nervous system (ANS) and hormonal system have been investigated. Methods: HRV was studied in a group of volunteers (17 people), involving non-smokers, i.e., who never smoked before (11), ex-smokers (4) and active smokers (2). ANDS and smoking simulators, including regular, nicotine-free and electronic cigarettes; tobacco heating systems; chewing gums and nicotine packs of oral fixation (nic-packs), were used. Blood pressure, levels of stress hormones in saliva and catecholamines in the blood were also monitored. Results: HRV analysis showed relatively small changes in HRV and in the other studied parameters with the systemic use of nic-packs with low and moderate nicotine contents (up to 6 mg) compared to other ANDS. Conclusions: The HRV method is proven to be a promising technique for evaluation of the risks associated with smoking, dual use of various ANDS and studying the biomedical aspects of smoking cessation. Nic-packs are shown to be leaders in biological safety among the studied ANDS. A sharp surge in the activity of the sympathetic division of the ANS within the first minutes of the use of nicotine packs implies that nicotine begins to act already at very low doses (before entering the blood physically in any significant amount) through fast signal transmission to the brain from the nicotinic and taste buds located in the mouth area.

Anhedonia and Suicide

Suicide is a leading cause of death, and presently, there is no definitive clinical indicator of future suicide behaviors. Anhedonia, a transdiagnostic symptom reflecting diminished ability to experience pleasure, has recently emerged as a risk factor for suicidal thoughts and behaviors (STBs). This overview, therefore, has the following aims. First, prior research relating anhedonia to STBs will be reviewed, with a particular focus on clarifying whether anhedonia is more closely associated with suicidal thoughts versus behaviors. Second, the National Institute of Mental Health's Research Domain Criteria Positive Valence Systems provide a useful heuristic to probe anhedonia across different units of analysis, including clinical symptoms, behaviors, neural mechanisms, and molecular targets. Accordingly, anhedonia-related constructs linked to STBs will be detailed as well as promising next steps for future research. Third, although anhedonia is not directly addressed in leading suicide theories, this review will provide potential inroads to explore anhedonia within diathesis-stress and interpersonal suicide frameworks. Last, novel approaches to treat anhedonia as a means of reducing STBs will be examined.

Effects of N-acetylcysteine on Noise Exposure-induced Oxidative Stress and Depressive- and Anxiety-like Behaviors in Adult Male Mice

Introduction:

Depression and anxiety are the most common psychiatric disorders. These conditions widely occur in industrial societies and severely affect individuals’ lives. N-Acetylcysteine (NAC) is a mucolytic compound with antioxidant and anti-inflammatory effects. This study aimed to investigate the potential therapeutic effects of NAC on chronic noise-induced depression- and anxiety-like behaviors in mice.

Methods:

Fifty male BALB/c mice were randomly divided into 5 groups, as follows: control, noise90 dB, noise110 dB, noise 90+NAC, and noise 110+NAC groups. Animals in the noise groups were exposed to 90 dB 2 h/day and 110 dB 2 h/day for 30 days. The NAC groups received NAC (325 mg/kg P.O.) 20 min after being exposed to noise. To evaluate depressive- and anxiety-like behaviors, the examined mice were subjected to the Open Field Test (OFT), Sucrose Preference Test (SPT), Tail Suspension Test (TST), and Elevated Plus Maze (EPM) tasks. At the end of the behavioral tests, the study animals were sacrificed. Accordingly, the levels of Malondialdehyde (MDA), Total Antioxidant Capacity (TAC), Superoxide Dismutase (SOD), and Glutathione Peroxidase (GPx) were determined in the Hippocampus (HIP) and the Prefrontal Cortex (PFC).

Results:

The obtained results suggested that noise exposure would induce anxiety- and depressive-like behaviors, being reversed by NAC administration. Moreover, chronic administration of NAC significantly increased antioxidant enzyme activities and reduced lipid peroxidation (MDA levels) in the PFC and HIP of noise-exposed mice.

Conclusion:

Our findings revealed that administrating NAC would reduce the adverse effects of noise on the brain and would exert anti-depressant and anxiolytic effects.

Inflammatory cytokines, complement factor H and anhedonia in drug-naïve major depressive disorder

OBJECTIVE

Anhedonia is a core symptom of major depressive disorder (MDD) and often associated with poor prognosis. The main objective of the present study was to explore the relationship between complement factor H (CFH), inflammatory cytokines and anhedonia in drug-naïve MDD patients.

METHODS

A total of 215 participants (61 MDD patients with anhedonia, 78 MDD patients without anhedonia, and 76 control subjects) were included. Severity of depression and levels of anhedonia were evaluated by Hamilton Rating Scale for Depression-17 (HAMD-17) and SHAPS (Snaith-Hamilton Pleasure Scale). Plasma levels of CFH, interleukin-6 (IL-6), IL-10 and tumor necrosis factor-α (TNF-α) were measured.

RESULTS

The plasma levels of CFH, IL-10 and TNF-α were higher in drug-naïve MDD patients than control subjects. Compared to MDD patients without anhedonia, patients with anhedonia showed higher levels of CFH and IL-6. The stepwise regression analysis revealed that IL-10, TNF-α, as well as IL-10 × TNF-α were associated with depressive symptoms measured by HAMD-17 in drug-naïve MDD patients, while only CFH levels were identified as a mediator factor for the severity of anhedonia in the patients.

CONCLUSION

MDD patients with anhedonia showed different inflammatory characteristics compared to patients without anhedonia. Our results provide novel evidence suggesting that increased plasma CFH levels may be a potential biomarker of anhedonia of subtyping MDD.

The Role of Glia in Addiction: Dopamine as a Modulator of Glial Responses in Addiction

Addiction is a chronic and potentially deadly disease considered a global health problem. Nevertheless, there is still no ideal treatment for its management. The alterations in the reward system are the most known pathophysiological mechanisms. Dopamine is the pivotal neurotransmitter involved in neuronal drug reward mechanisms and its neuronal mechanisms have been intensely investigated in recent years. However, neuroglial interactions and their relation to drug addiction development and maintenance of drug addiction have been understudied. Many reports have found that most neuroglial cells express dopamine receptors and that dopamine activity may induce neuroimmunomodulatory effects. Furthermore, current research has also shown that pro- and anti-inflammatory molecules modulate dopaminergic neuron activity. Thus, studying the immune mechanisms of dopamine associated with drug abuse is vital in researching new pathophysiological mechanisms and new therapeutic targets for addiction management.

Diet and companionship modulate pain via a serotonergic mechanism

Treatment of severe chronic and acute pain in sickle cell disease (SCD) remains challenging due to the interdependence of pain and psychosocial modulation. We examined whether modulation of the descending pain pathway through an enriched diet and companionship could alleviate pain in transgenic sickle mice. Mechanical and thermal hyperalgesia were reduced significantly with enriched diet and/or companionship. Upon withdrawal of both conditions, analgesic effects observed prior to withdrawal were diminished. Serotonin (5-hydroxytryptamine, 5-HT) was found to be increased in the spinal cords of mice provided both treatments. Additionally, 5-HT production improved at the rostral ventromedial medulla and 5-HT accumulated at the dorsal horn of the spinal cord of sickle mice, suggesting the involvement of the descending pain pathway in the analgesic response. Modulation of 5-HT and its effect on hyperalgesia was also investigated through pharmaceutical approaches. Duloxetine, a serotonin-norepinephrine reuptake inhibitor, showed a similar anti-nociceptive effect as the combination of diet and companionship. Depletion of 5-HT through p-chlorophenylalanine attenuated the anti-hyperalgesic effect of enriched diet and companionship. More significantly, improved diet and companionship enhanced the efficacy of a sub-optimal dose of morphine for analgesia in sickle mice. These findings offer the potential to reduce opioid use without pharmacological interventions to develop effective pain management strategies.

DAT1 and Its Psychological Correlates in Children with Avoidant/Restrictive Food Intake Disorder: A Cross-Sectional Pilot Study

International research has underlined the role played by children’s and maternal psychopathological symptoms on the onset of avoidant/restrictive food intake disorder (ARFID) in early childhood. No study has considered the possible interplay between children’s dopamine transporter (DAT1) genotype and methylation, dysregulation problems and maternal psychopathological risk. This study aimed to investigate the complex relationship between these variables, considering the possible mediation role played by children’s DAT1 methylation on the relationship between mothers’ psychopathological risk and children’s dysregulation problems, moderated by children’s DAT1 genotype. Our sample consisted of 94 early children and their mothers, divided into four subgroups, based on children’s ARFID subtypes (irritable/impulsive (I/I), sensory food aversions (SFA), post-traumatic feeding disorders subtypes (PTFD), and a non-clinical group (NC)). We addressed children’s dysregulation problems and maternal psychopathological risk, and collected children’s DNA through buccal swabs. Results showed that children’s 9/x genotype was associated with PTFD and NC groups, whereas the 10/10 genotype was associated with the SFA group, with large effect size. There were significant large differences in the study groups on children’s DAT1 total methylation, children’s dysregulation problems, and maternal psychopathological risk. Children’s DAT1 methylation did not mediate the relationship between mother’s psychopathological risk and children’s dysregulation problems, but there was a significant large direct effect. Children’s 9/x genotype moderated the relationship between maternal psychopathological risk and children’s DAT1 methylation but, respectively, with a large and small effect. Our pilot study suggested that the relationship between children’s DAT1 genotype and methylation, dysregulation problems, and maternal psychopathological risk has a crucial contribution to ARFID.

Graph theory analysis of the dopamine D2 receptor network in Parkinson's disease patients with cognitive decline

Cognitive decline in Parkinson's disease (PD) is a common sequela of the disorder that has a large impact on patient well-being. Its physiological etiology, however, remains elusive. Our study used graph theory analysis to investigate the large-scale topological patterns of the extrastriatal dopamine D2 receptor network. We used positron emission tomography with [¹¹ C]FLB-457 to measure the binding potential of cortical dopamine D2 receptors in two networks: the meso-cortical dopamine network and the meso-limbic dopamine network. We also investigated the application of partial volume effect correction (PVEC) in conjunction with graph theory analysis. Three groups were investigated in this study divided according to their cognitive status as measured by the Montreal Cognitive Assessment score, with a score ≤25 considered cognitively impaired: (a) healthy controls (n = 13, 11 female), (b) cognitively unimpaired PD patients (PD-CU, n = 13, 5 female), and (c) PD patients with mild cognitive impairment (PD-MCI, n = 17, 4 female). In the meso-cortical network, we observed increased small-worldness, normalized clustering, and local efficiency in the PD-CU group compared to the PD-MCI group, as well as a hub shift in the PD-MCI group. Compensatory reorganization of the meso-cortical dopamine D2 receptor network may be responsible for some of the cognitive preservation observed in PD-CU. These results were found without PVEC applied and PVEC proved detrimental to the graph theory analysis. Overall, our findings demonstrate how graph theory analysis can be used to detect subtle changes in the brain that would otherwise be missed by regional comparisons of receptor density.

Metabolomic insights into the lasting impacts of early-life exposure to BDE-47 in mice

Early-life exposure to toxicants may have lasting effects that adversely impact later development. Thus, although the production and use of a toxicant have been banned, the risk to previously exposed individuals may continue. BDE-47, a component of commercial penta-BDEs, is a persistent organic pollutant with demonstrated neurotoxicity. To investigate the persistent effects of BDE-47 and the mechanisms thereof, we employed a metabolomics approach to analyze the brain, blood and urine of mice exposed to BDE-47 for 28 days and then 3 months post-exposure. In the brain, BDE-47 was detectable just after exposure but was below the limit of detection (LOD) 3 months later. However, the metabolomic alterations caused by early-life exposure to BDE-47 persisted. Potential biomarkers related to these alterations included phosphatidylcholine, lysophosphatidylcholine, sphingomyelin and several amino acids and biogenic amines. The metabolic pathways involved in the response to BDE-47 in the brain were mainly those related to glycerophospholipid metabolism, sphingomyelin metabolism and neurotransmitter regulation. Thus, our study demonstrates the utility of metabolomics, as the omics most closely reflecting the phenotype, in exploring the mechanisms underlying the lasting effects induced by early-life BDE-47 exposure.

A Practical Approach to Acute Postoperative Pain Management in Chronic Pain Patients

In the United States, more than 100 million people suffer from chronic pain. Among patients presenting for surgery, about one in four have chronic pain. Acute perioperative pain management in this population is challenging because many patients with chronic pain require long-term opioids for the management of this pain, which may result in tolerance, physical dependence, addiction, and opioid-induced hyperalgesia. These challenges are compounded by the ongoing opioid epidemic that has resulted in calls for a reduction in opioid use, with a concurrent increase in the number of patients with chronic opioid exposure presenting for surgery. This article aims to summarize practical considerations for acute postoperative pain management in patients with chronic pain conditions. A patient-centered acute pain management plan, including nonopioid analgesics, regional anesthesia, and careful selection of opioid medications, can lead to adequate analgesia and satisfaction with care. Also, a meticulous rotation from one opioid to another may decrease opioid requirement, increase analgesic effectiveness, and improve satisfaction with care.

Reward related ventral striatal activity and differential response to sertraline versus placebo in depressed individuals

Medications to treat major depressive disorder (MDD) are not equally effective across patients. Given that neural response to rewards is altered in MDD and given that reward-related circuitry is modulated by dopamine and serotonin, we examined, for the first time, whether reward-related neural activity moderated response to sertraline, an antidepressant medication that targets these neurotransmitters. A total of 222 unmedicated adults with MDD randomized to receive sertraline (n = 110) or placebo (n = 112) in the Establishing Moderators and Biosignatures of Antidepressant Response in Clinical Care (EMBARC) study completed demographic and clinical assessments, and pretreatment functional magnetic resonance imaging while performing a reward task. We tested whether an index of reward system function in the ventral striatum (VS), a key reward circuitry region, moderated differential response to sertraline versus placebo, assessed with the Hamilton Rating Scale for Depression (HSRD) over 8 weeks. We observed a significant moderation effect of the reward index, reflecting the temporal dynamics of VS activity, on week-8 depression levels (Fs ≥ 9.67, ps ≤ 0.002). Specifically, VS responses that were abnormal with respect to predictions from reinforcement learning theory were associated with lower week-8 depression symptoms in the sertraline versus placebo arms. Thus, a more abnormal pattern of pretreatment VS dynamic response to reward expectancy (expected outcome value) and prediction error (difference between expected and actual outcome), likely reflecting serotonergic and dopaminergic deficits, was associated with better response to sertraline than placebo. Pretreatment measures of reward-related VS activity may serve as objective neural markers to advance efforts to personalize interventions by guiding individual-level choice of antidepressant treatment.

The roles of cannabinoid CB1 and CB2 receptors in cocaine-induced behavioral sensitization and conditioned place preference in mice

RATIONALE

Cocaine is a psychostimulant drug that facilitates monoaminergic neurotransmission. The endocannabinoid system, comprising the cannabinoid receptors (CB₁R and CB₂R), the endocannabinoids, and their metabolizing-enzymes, modulates the mesolimbic dopaminergic pathway and represents a potential target for the treatment of addiction.

OBJECTIVES

Here, we tested the hypothesis that the cannabinoid receptors are implicated in cocaine-induced motor sensitization, conditioned place preference (CPP), and hippocampal activation.

METHODS

Male Swiss mice received injections of AM251 (CB₁R antagonist; 0.3-10 mg/kg) or JWH133 (CB₂R agonist; 1-10 mg/kg) before acquisition or expression of cocaine (20 mg/kg)-induced sensitization and CPP. After the CPP test, cFos-staining was employed as a marker of neuronal activation in the hippocampus.

RESULTS

AM251 inhibited the acquisition (0.3, 1, and 3 mg/kg) and expression (1 and 3 mg/kg) of sensitization, as well as the acquisition (10 mg/kg) of CPP. JWH133 inhibited the acquisition (0.3 and 1 mg/kg) and expression (1 and 3 mg/kg) of both sensitization and CPP. JWH133 effects were reversed by AM630 (CB₂R antagonist; 5 mg/kg). AM251 and JWH133 also prevented neuronal activation (c-Fos expression) in the hippocampus of CPP-exposed animals.

CONCLUSIONS

CB₁R and CB₂R have opposite roles in modulating cocaine-induced sensitization and CPP, possibly by preventing neuronal activation in the hippocampus.

Is vaping better than smoking for cardiorespiratory and muscle function?

Cigarette smoking is a risk factor for respiratory disorders, cardiovascular diseases and even decrements in muscle function. Electronic cigarette use (vaping) is considered a healthier alternative to cigarette smoking and may help in smoking cessation. However, the effects of vaping are not clear yet and particularly the long-term effects of vaping are largely unknown. Some reports suggest that vaping maybe as harmful for e.g. respiratory function, as cigarette smoking. In this narrative review the effects of vaping and cigarette smoking on respiratory, cardiovascular and muscle function are compared. Overall, vaping has been found to cause similar effects as smoking on lung function and cardiovascular function. Future studies are needed to clarify the severity of smoking- and vaping-induced decrements on muscle function.

Fluorescent Biosensors for Neurotransmission and Neuromodulation: Engineering and Applications

Understanding how neuronal activity patterns in the brain correlate with complex behavior is one of the primary goals of modern neuroscience. Chemical transmission is the major way of communication between neurons, however, traditional methods of detection of neurotransmitter and neuromodulator transients in mammalian brain lack spatiotemporal precision. Modern fluorescent biosensors for neurotransmitters and neuromodulators allow monitoring chemical transmission in vivo with millisecond precision and single cell resolution. Changes in the fluorescent biosensor brightness occur upon neurotransmitter binding and can be detected using fiber photometry, stationary microscopy and miniaturized head-mounted microscopes. Biosensors can be expressed in the animal brain using adeno-associated viral vectors, and their cell-specific expression can be achieved with Cre-recombinase expressing animals. Although initially fluorescent biosensors for chemical transmission were represented by glutamate biosensors, nowadays biosensors for GABA, acetylcholine, glycine, norepinephrine, and dopamine are available as well. In this review, we overview functioning principles of existing intensiometric and ratiometric biosensors and provide brief insight into the variety of neurotransmitter-binding proteins from bacteria, plants, and eukaryotes including G-protein coupled receptors, which may serve as neurotransmitter-binding scaffolds. We next describe a workflow for development of neurotransmitter and neuromodulator biosensors. We then discuss advanced setups for functional imaging of neurotransmitter transients in the brain of awake freely moving animals. We conclude by providing application examples of biosensors for the studies of complex behavior with the single-neuron precision.

Musical sonification improves motor control in Parkinson's disease: a proof of concept with handwriting

A growing number of studies postulate the use of music to improve motor control in patients with Parkinson's disease (PD). The effects of music are greatly variable from one individual to the other and do not always reach the expected benefits. This study aimed to optimize the use of music in the management of movement disorders inherent to PD in a handwriting task. We developed and tested musical sonification (MS), a method that transforms in real-time kinematic variables into music. Twelve patients with PD, on medication, and 12 healthy controls were recruited in a pretest/training/posttest design experiment. Three training sessions were compared, for which participants were asked to produce graphomotor exercises: one session with music (unrelated to handwriting), one with MS (controlled by handwriting), and one in silence. Results showed that the performance in training was better under MS than under silence or background music, for both groups. After training, the benefits of MS were still present for both groups, with a higher effect for PD patients than for control group. Our results provide a proof of concept to consider MS as a relevant auditory guidance strategy for movement rehabilitation in patients with PD.

Behavioral Changes and Neuronal Damage in Rhesus Monkeys after 10 Weeks of Ketamine Administration Involve Prefrontal Cortex Dopamine D2 Receptor and Dopamine Transporter

The dopamine D2 receptor (DRD2) and dopamine transporter (DAT) play a regulatory role in dopaminergic neurotransmission and thus play an important role in drug addiction. The prefrontal cortex (PFC), a critical part of the mesencephalic dopaminergic system, is thought to be involved in the development and maintenance of drug addiction. The addiction to ketamine is thought to induce behavioral effects primarily through actions on the central nervous system. However, the neural mechanism underlying the effects of ketamine addiction remains unclear. In this study, we investigate the involvement of PFC DRD2 and DAT in ketamine addiction effects after ketamine administration for 10 weeks in nonhuman primates. To this end, after administering ketamine to rhesus monkeys for 10 weeks, we assessed changes in body weight and behavior. Additionally, neuronal changes in the PFC were examined by hematoxylin and eosin (HE) staining; the DRD2 and DAT mRNA and protein expression levels in the PFC were determined by real-time PCR and Western blot analysis, respectively. After 10-week ketamine administration, the assessment of the manifestations of toxicity in rhesus monkeys revealed significant changes in body weight and behavior, decreased DRD2 and DAT mRNA and protein expression in the PFC, and histological abnormalities including neuronal eosinophilia, pyknosis and disorderly arrangement of neurons in the PFC. These results suggest that the reduced expression of DRD2 and DAT in PFC could be involved in the behavioral and the neurological changes induced by ketamine administration, which may play an important role in the molecular mechanisms of ketamine addiction.

Multilevel Impacts of Iron in the Brain: The Cross Talk between Neurophysiological Mechanisms, Cognition, and Social Behavior

Iron is a critical element for most organisms, which plays a fundamental role in the great majority of physiological processes. So much so, that disruption of iron homeostasis has severe multi-organ impacts with the brain being particularly sensitive to such modifications. More specifically, disruption of iron homeostasis in the brain can affect neurophysiological mechanisms, cognition, and social behavior, which eventually contributes to the development of a diverse set of neuro-pathologies. This article starts by exploring the mechanisms of iron action in the brain and follows with a discussion on cognitive and behavioral implications of iron deficiency and overload and how these are framed by the social context. Subsequently, we scrutinize the implications of the disruption of iron homeostasis for the onset and progression of psychosocial disorders. Lastly, we discuss the links between biological, psychological, and social dimensions and outline potential avenues of research. The study of these interactions could ultimately contribute to a broader understanding of how individuals think and act under physiological and pathophysiological conditions.

Intervention changes acoustic peak frequency and mesolimbic neurochemistry in the Pink1-/- rat model of Parkinson disease

The neural mechanisms underlying behavioral therapy for vocal acoustic deficits in patients with Parkinson disease is unknown. A primary hypothesis is that voice therapy may modulate mesolimbic brainstem regions, including the ventral tegmental area (VTA). The VTA is implicated in ultrasonic call peak frequency, involved in rewarding behaviors, and impacted by Parkinsonism. We tested the hypothesis that chronic (daily) behavioral vocal exercise of male Pink1-/- rats would alter ultrasonic vocalization acoustics and mesolimbic neurochemistry (catecholamines, GABA, mu-opioid receptor) compared to three different controls: sham-exercised Pink1-/-, unexercised Pink1-/-, and unexercised wildtype (WT) rats. A sub-hypothesis is that sham-exercise rats may exhibit changes to VTA neurochemistry as a result of a type or rewarding intervention. Results demonstrate that average bandwidth (frequency range) of ultrasonic vocalizations did not differ between WT, Pink1-/- no exercise vs. sham and vocal-exercise rats. However, average peak frequency is significantly reduced in vocal-exercised Pink1-/- rats compared to Pink1-/- no exercise, and WT groups. Unexpectedly, there were no significant acoustic differences between the vocal- and sham-exercised groups. There were no differences in catecholamine protein concentrations or tyrosine hydroxylase mRNA expression in the VTA between any of the groups. However, there was significant upregulation of all GABA-related genes in both vocal- and sham-exercised Pink1-/- rats (Gad1, Gad2, Gls, Glul); this finding was confirmed with follow up quantitative Western blotting for GAD. Additionally, there were differential results for mu-opioid receptor quantification in the VTA: vocal-exercised Pink1-/- rats showed increased mRNA expression for mu-opioid receptors whereas Western blotting indicated decreased protein levels in all Pink1-/- rats compared to WT controls suggesting the possible onset of pathology in this model. These data demonstrate modulatory effects of a rewarding behavioral paradigm on ultrasonic vocalization peak frequency. The results suggest that neuromodulators such as GABA and opioid activity, as well as the rewarding aspects of therapy may play a key role in shaping vocal treatments.

Human prenatal exposure to polychlorinated biphenyls (PCBs) and risk behaviors in adolescence

Polychlorinated biphenyls (PCBs) are chemicals used in a variety of products before they were widely banned due to toxic effects in humans and wildlife. Because of continued persistence and ubiquity of these contaminants, risk of exposure to people living in industrialized countries is still high. Experimental research show that developmental exposure to PCB may alter function of brain pleasure centers and potentially influence disinhibitory behaviors, including tobacco and alcohol use. Yet, the potential effects of developmental PCB exposure on adolescent substance use have not been studied in humans. We used the Child Health and Development Studies (CHDS), a prospective birth cohort study in the Oakland and East Bay areas of California, to investigate associations between prenatal exposure to PCB congeners (66, 74, 99, 118, 138, 153, 170, 180, 187, and 203) and later disinhibitory behaviors in adolescents, specifically alcohol consumption and smoking, in a randomly selected sample (n = 554). Total prenatal PCB exposure was not associated with disinhibitory behaviors, among adolescents. However, the adjusted odds ratio (aOR) for being a current smoker, was higher in subjects within the third quartile of maternal PCB 66 exposure compared to those below the median (aOR = 1.93; 95% CI 1.05, 3.55). The aOR for drinking >2 alcoholic beverages per week, were also higher for adolescents within the third (aOR = 1.46; 95% CI 0.86, 2.47) and fourth quartile of PCB 66 exposure (aOR = 1.39; 95% CI 0.83, 2.35), but the differences did not reach statistical significance. These results suggest that this specific PCB congener may play a role inducing neurodevelopmental alterations that could potentially increase the risk of becoming a long-term user of tobacco and possibly alcohol. There were no notable differences between magnitude or direction of effect between boys and girls. Future replicate analyses with larger longitudinal samples and animal experimental studies of potential underlying mechanisms are warranted.

Role of the galanin N-terminal fragment (1-15) in anhedonia: Involvement of the dopaminergic mesolimbic system

BACKGROUND

Anhedonia is a core feature of depressive disorders. The galanin N-terminal fragment (1-15) plays a role in mood regulation since it induces depression and anxiogenic-like effects in rats. In this study, we analysed galanin N-terminal fragment (1-15) actions in anhedonic-like behaviours in rats using operant and non-operant tests and the areas involved with these effects.

METHODS

Galanin N-terminal fragment (1-15) effects were analysed in saccharin self-administration, sucrose preference, novelty-suppressed feeding and female urine sniffing tests. The areas involved in galanin N-terminal fragment (1-15)-mediated effects were studied with positron emission tomography for in vivo imaging, and we analysed the ventral tegmental area and nucleus accumbens. Galanin N-terminal fragment (1-15) had effects on the mRNA expression of the dopamine transporters Dat and Vmat2; the C-Fos gene; the dopamine receptors D1, D2, D3, D5; and the galanin receptors 1 and 2.

RESULTS

Galanin N-terminal fragment (1-15) at a concentration of 3 nmol induced a strong anhedonia-like phenotype in all tests. The involvement of galanin receptor 2 was demonstrated with the galanin receptor 2 antagonist M871 (3 nmol). The 18F-fluorodeoxyglucose positron emission tomography images indicated the action of galanin N-terminal fragment (1-15) over several nuclei of the limbic system. Galanin N-terminal fragment (1-15)-mediated effects also involved changes in the expression of Dat, Vmat2, D3 and galanin receptors in the ventral tegmental area as well as the expression of C-Fos, D1, D2 and D3 and TH immunoreactivity in the nucleus accumbens.

CONCLUSIONS

Our results indicated that galanin N-terminal fragment (1-15) exerts strong anhedonic-like effects and that this effect was accompanied by changes in the dopaminergic mesolimbic system. These results may provide a basis for the development of novel therapeutic strategies using galanin N-terminal fragment (1-15) analogues for the treatment of depression and reward-related diseases.

Shame in Parkinson'S Disease: A Review

Shame is a self-conscious emotion marked by an intensely negative self-evaluation. It is exhibited by an individual upon realizing that she/he has violated an important (usually social) norm. Shame can be a source of emotional distress leading to social withdrawal and depression, with a significant negative impact on quality of life. In Parkinson’s disease (PD), shame is rarely addressed. Based on reports of persons affected with Parkinson’s disease (PwP) as well as a literature review, this article describes PD-related shame. PD-related shame may emerge from motor and non-motor symptoms, from self-perception of inadequacy due to loss of autonomy and need for help, or from perceived deterioration of body image. The neurobiology of shame delineates neuronal networks involved in cognitive and emotions regulation, self-representation and representation of the others mental states. Although this hypothesis remains to be demonstrated, these substrates could be modulated, at least partially, by dopaminergic depletion related to PD, which may open a window for pharmacotherapy. Owing to the negative impact that shame can produce, shame should be actively explored and addressed in the individual PwP. Teaching PwP how to develop resilience to shame may be a useful strategy in preventing the vicious circle of shame. The paucity of existing data on prevalence and management of PD-specific shame contrasts with the manifold reported situations inducing suffering from shame. There is a crucial need for further investigations of shame in PD and the development of interventions to reduce its impact on PwP’s quality of life.

Relating Sensory, Cognitive, and Neural Factors to Older Persons' Perceptions about Happiness: An Exploratory Study

Despite increased rates of disease, disability, and social losses with aging, seniors consistently report higher levels of subjective well-being (SWB), a construct closely related to happiness, than younger adults. In this exploratory study, we utilized an available dataset to investigate how aspects of health commonly deteriorating with age, including sensory (i.e., vision and hearing) and cognitive status, relate to variability in self-described contributors to happiness. Community-dwelling seniors (n = 114) responded to a single-item prompt: “name things that make people happy.” 1731 responses were categorized into 13 domains of SWB via structured content analysis. Sensory health and cognition were assessed by Snellen visual acuity, pure-tone audiometry, and in-person administration of the Brief Test of Adult Cognition by Telephone (BTACT) battery. A subset of eligible participants (n = 57) underwent functional magnetic resonance imaging (fMRI) to assess resting state functional connectivity (FC) within a previously described dopaminergic network associated with reward processing. SWB response patterns were relatively stable across gender, sensory status, and cognitive performance with few exceptions. For example, hearing-impaired participants listed fewer determinants of SWB (13.59 vs. 17.16; p < 0.001) and were less likely to name things in the “special events” category. Participants with a higher proportion of responses in the “accomplishments” domain (e.g., winning, getting good grades) demonstrated increased FC between the ventral tegmental area and nucleus accumbens, regions implicated in reward and motivated behavior. While the framework for determinants of happiness among seniors was largely stable across the factors assessed here, our findings suggest that subtle changes in this construct may be linked to sensory loss. The possibility that perceptions about determinants of happiness might relate to differences in intrinsic connectivity within reward-related brain networks also warrants further investigation.

In further defense of nonclinical abuse liability testing of biologics

Risk assessment is not a choice. Drug Abuse Liability (DAL) is mandated under international and national drug control statutes for all drugs targeting the CNS. Once administered to humans many biologics may have long-lived or permanent physiological effects that make DAL testing arduous. We respond to premises of a recently published position on DAL testing of biologics by de Zafra et al. (2018). We propose that, at a minimum, Sponsors submitting a Biologics Licensure Application (BLA) must think "outside the box" and include differential study designs for the same three core small NME assays detailed in the current DAL guidelines (self-administration, drug discrimination, and dependence liability). Abuse liability testing for drug scheduling decisions for marketing approval are not excluded or limited from risk assessment analysis simply because the entity is a biologic. In fact, more robust study designs may be necessary to address alterations in the reinforcing and discriminative stimulus effects of common drugs of abuse, as well as the dependence liability of the biologic, itself.

Reward Processing in Depression: A Conceptual and Meta-Analytic Review Across fMRI and EEG Studies

OBJECTIVE

A role for aberrant reward processing in the pathogenesis of depression has long been proposed. However, no review has yet examined its role in depression by integrating conceptual and quantitative findings across functional MRI (fMRI) and EEG methodologies. The authors quantified these effects, with an emphasis on development.

METHOD

A total of 38 fMRI and 12 EEG studies were entered into fMRI and EEG meta-analyses. fMRI studies primarily examined reward anticipation and reward feedback. These were analyzed using the activation likelihood estimation method. EEG studies involved mainly the feedback-related negativity (FRN) event-related potential, and these studies were analyzed using random-effects meta-analysis of the association between FRN and depression.

RESULTS

Analysis of fMRI studies revealed significantly reduced striatal activation in depressed compared with healthy individuals during reward feedback. When region-of-interest analyses were included, reduced activation was also observed in reward anticipation, an effect that was stronger in individuals under age 18. FRN was also significantly reduced in depression, with pronounced effects in individuals under age 18. In longitudinal studies, reduced striatal activation in fMRI and blunted FRN in EEG were found to precede the onset of depression in adolescents.

CONCLUSIONS

Taken together, the findings show consistent neural aberrations during reward processing in depression, namely, reduced striatal signal during feedback and blunted FRN. These aberrations may underlie the pathogenesis of depression and have important implications for development of new treatments.

The Neural Mechanism Underlying Cognitive and Emotional Processes in Creativity

Creativity is related to both cognition and emotion, which are the two major mental processes, interacting with each other to form psychological processes. Emotion is the major driving force of almost all creativities, sometimes in an unconscious way. Even though there are many studies concerning the relationship between creativity and cognition, there are few studies about the neural mechanisms of the emotional effects on creativity. Here, we introduce a novel model to explain the relationship between emotions and creativities: Three Primary Color model, which proposes that there are four major basic emotions; these basic emotions are subsided by three monoamines, just like the three primary colors: dopamine-joy, norepinephrine-stress (fear and anger), and serotonin-punishment. Interestingly, these three neuromodulators play similar roles in creativity, whose core features are value and novelty (surprise), like the characteristics of the core features of basic emotions (hedonic value and arousal value). Dysfunctions of these neuromodulators may be the reasons for both psychopathology and creativity, in that they can change the thinking styles such as novelty seeking behavior, hyper-connectivity of brain areas, and/or cognitive disinhibition to induce both creativity and psychopathology. This new model will not only help researchers understand the dynamics of basic emotion elements, it can also bring an entirely new perspective into the relationship between psychopathology and creativity.

Morin as a Preservative for Delaying Senescence of Banana

Banana is a climacteric fruit with desirable palatability and high nutritional value. It ripens rapidly accompanied with metabolite changes during postharvest storage. In this work, morin was applied to treat banana to delay senescence. Nuclear magnetic resonance (NMR) spectroscopy was used to monitor the changes of metabolite composition and levels in banana. The results showed that morin significantly delayed the changes of color and firmness. 1D and 2D NMR spectra reflected that the levels and composition of metabolites were changed with the senescence initiation. The principal component analysis revealed that the first principal components responsible for banana senescence were carbohydrates, amino acids, lipids and phenolics. Morin treatment delayed the transformation of starch to glucose, fructose and sucrose, accelerated the accumulations of alanine and γ-Amino-butyrate (GABA), postponed the generations of valine and l-aspartic acid, suppressed the degradation of saponin a. It indicated that morin was effective in delaying banana senescence.

Mechanisms underlying the association between insomnia, anxiety, and depression in adolescence: Implications for behavioral sleep interventions

There is robust evidence of an association between insomnia, anxiety, and depression in adolescence. The aim of this review is to describe and synthesize potential mechanisms underlying this association and explore implications for the design of adolescent behavioral sleep interventions. Specifically, we examine whether insomnia symptoms are a mechanism for the development of internalizing symptoms in adolescence and whether sleep interventions are an effective treatment for both insomnia and internalizing symptoms in adolescence because they target the shared mechanisms underlying these disorders. Research using different methodologies points to the role of sequential, parallel, and interacting mechanisms. In this paper, we review a wide range of relevant biological (i.e., polymorphisms and dysregulation in serotonin, dopamine, and circadian clock genes; alterations in corticolimbic and mesolimbic brain circuits; cortisol reactivity to stress; inflammatory cytokine dysregulation; biased memory consolidation; changes in sleep architecture), psychological (i.e., cognitive inflexibility, interpretational biases, judgment biases, negative attribution styles, worry, rumination, biased attention to threat, dysfunctional beliefs and attitudes about sleep, misperception of sleep deficit), and social mechanisms (i.e., reduced and impaired social interactions, unhelpful parenting behaviors, family stress) and propose an integrative multilevel model of how these phenomena may interact to increase vulnerability to both insomnia and internalizing disorders. Several 'biopsychosocial' mechanisms hold promise as viable treatment targets for adolescent behavioral sleep interventions, which may reduce both insomnia and internalizing symptoms.

Pharmacological interventions for apathy in Alzheimer's disease

BACKGROUND

Despite the high prevalence of apathy in Alzheimer's disease (AD), and its harmful effects, there are currently no therapies proven to treat this symptom. Recently, a number of pharmacological therapies have been investigated as potential treatments for apathy in AD.

OBJECTIVES

Objective 1: To assess the safety and efficacy of pharmacotherapies for the treatment of apathy in Alzheimer's disease (AD).Objective 2: To assess the effect on apathy of pharmacotherapies investigated for other primary outcomes in the treatment of AD.

SEARCH METHODS

We searched the Specialized Register of the Cochrane Dementia and Cognitive Improvement Group (ALOIS), MEDLINE, Embase, CINAHL, PsycINFO, LILACS, ClinicalTrials.gov and the World Health Organization (WHO) portal, ICTRP on 17 May 2017.

SELECTION CRITERIA

Eligible studies were double-blind, randomized, placebo-controlled trials (RCTs) investigating apathy as a primary or secondary outcome in people with AD.

DATA COLLECTION AND ANALYSIS

Three review authors extracted data. We assessed the risks of bias of included studies using Cochrane methods, and the overall quality of evidence for each outcome using GRADE methods. We calculated mean difference (MD), standardized mean difference (SMD) or risk ratio (RR) with 95% confidence intervals on an intention-to-treat basis for all relevant outcome measures.

MAIN RESULTS

We included 21 studies involving a total of 6384 participants in the quantitative analyses. Risk of bias is very low to moderate. All studies reported appropriate methods of randomization and blinding. Most studies reported appropriate methods of allocation concealment. Four studies, three with methylphenidate and one with modafinil, had a primary aim of improving apathy. In these studies, all participants had clinically significant apathy at baseline. Methylphenidate may improve apathy compared to placebo. This finding was present when apathy was assessed using the apathy evaluation scale (AES), which was used by all three studies investigating methylphenidate: MD -4.99, 95% CI -9.55 to -0.43, n = 145, 3 studies, low quality of evidence, but not when assessed with the neuropsychiatric inventory (NPI)-apathy subscale, which was used by two of the three studies investigating methylphenidate: MD -0.08, 95% CI -3.85 to 3.69, n = 85, 2 studies, low quality of evidence. As well as having potential benefits for apathy, methylphenidate probably also slightly improves cognition (MD 1.98, 95% CI 1.06 to 2.91, n = 145, 3 studies, moderate quality of evidence), and probably improves instrumental activities of daily living (MD 2.30, 95% CI 0.74 to 3.86, P = 0.004, n = 60, 1 study, moderate quality of evidence), compared to placebo. There may be no difference between methylphenidate and placebo in the risk of developing an adverse event: RR 1.28, 95% CI 0.67 to 2.42, n = 145, 3 studies, low quality of evidence. There was insufficient evidence from one very small study of modafinil to determine the effect of modafinil on apathy assessed with the FrSBe-apathy subscale: MD 0.27, 95% CI -3.51 to 4.05, n = 22, 1 study, low quality of evidence. In all other included studies, apathy was a secondary outcome and participants were not selected on the basis of clinically significant apathy at baseline. We considered the evidence on apathy from these studies to be indirect and associated with publication bias. There was low or very low quality of evidence on cholinesterase inhibitors (ChEIs) (six studies), ChEI discontinuation (one study), antipsychotics (two studies), antipsychotic discontinuation (one study), antidepressants (two studies), mibampator (one study), valproate (three studies) and semagacestat (one study).

AUTHORS' CONCLUSIONS

Methylphenidate may demonstrate a benefit for apathy and may have slight benefits for cognition and functional performance in people with AD, but this finding is associated with low-quality evidence. Our meta-analysis is limited by the small number of studies within each drug class, risk of bias, publication bias, imprecision and inconsistency between studies. Additional studies should be encouraged targeting people with AD with clinically significant apathy which investigate apathy as a primary outcome measure, and which have a longer duration and a larger sample size. This could increase the quality of evidence for methylphenidate, and may confirm whether or not it is an effective pharmacotherapy for apathy in AD.