The role of oxytocin in delay of gratification and flexibility in non-social decision making

Oxytocin is well-known for its impact on social cognition. This specificity for the social domain, however, has been challenged by findings suggesting a domain-general allostatic function for oxytocin by promoting future-oriented and flexible behavior. In this pre-registered study, we tested the hypothesized domain-general function of oxytocin by assessing the impact of intranasal oxytocin (24 IU) on core aspects of human social (inequity aversion) and non-social decision making (delay of gratification and cognitive flexibility) in 49 healthy volunteers (within-subject design). In intertemporal choice, patience was higher under oxytocin than under placebo, although this difference was evident only when restricting the analysis to the first experimental session (between-group comparison) due to carry-over effects. Further, oxytocin increased cognitive flexibility in reversal learning as well as generosity under conditions of advantageous but not disadvantageous inequity. Our findings show that oxytocin affects both social and non-social decision making, supporting theoretical accounts of domain-general functions of oxytocin.

Dopaminergic and opioidergic regulation during anticipation and consumption of social and nonsocial rewards

The observation of animal orofacial and behavioral reactions has played a fundamental role in research on reward but is seldom assessed in humans. Healthy volunteers (N = 131) received 400 mg of the dopaminergic antagonist amisulpride, 50 mg of the opioidergic antagonist naltrexone, or placebo. Subjective ratings, physical effort, and facial reactions to matched primary social (affective touch) and nonsocial (food) rewards were assessed. Both drugs resulted in lower physical effort and greater negative facial reactions during reward anticipation, especially of food rewards. Only opioidergic manipulation through naltrexone led to a reduction in positive facial reactions to liked rewards during reward consumption. Subjective ratings of wanting and liking were not modulated by either drug. Results suggest that facial reactions during anticipated and experienced pleasure rely on partly different neurochemical systems, and also that the neurochemical bases for food and touch rewards are not identical.

Anhedonia in chronic pain and prescription opioid misuse

BACKGROUND

Both acute and chronic pain can disrupt reward processing. Moreover, prolonged prescription opioid use and depressed mood are common in chronic pain samples. Despite the prevalence of these risk factors for anhedonia, little is known about anhedonia in chronic pain populations.

METHODS

We conducted a large-scale, systematic study of anhedonia in chronic pain, focusing on its relationship with opioid use/misuse, pain severity, and depression. Chronic pain patients across four distinct samples (N = 488) completed the Snaith-Hamilton Pleasure Scale (SHAPS), measures of opioid use, pain severity and depression, as well as the Current Opioid Misuse Measure (COMM). We used a meta-analytic approach to determine reference levels of anhedonia in healthy samples spanning a variety of countries and diverse age groups, extracting SHAPS scores from 58 published studies totaling 2664 psychiatrically healthy participants.

RESULTS

Compared to healthy samples, chronic pain patients showed higher levels of anhedonia, with ~25% of patients scoring above the standard anhedonia cut-off. This difference was not primarily driven by depression levels, which explained less than 25% of variance in anhedonia scores. Neither opioid use duration, dose, nor pain severity alone was significantly associated with anhedonia. Yet, there was a clear effect of opioid misuse, with opioid misusers (COMM ⩾13) reporting greater anhedonia than non-misusers. Opioid misuse remained a significant predictor of anhedonia even after controlling for pain severity, depression and opioid dose.

CONCLUSIONS

Study results suggest that both chronic pain and opioid misuse contribute to anhedonia, which may, in turn, drive further pain and misuse.

Anticipation of monetary reward in amygdala, insula, caudate are predictors of pleasure sensitivity to d-Amphetamine administration

BACKGROUND

Drug addiction and dependence continue as an unresolved source of morbidity and mortality. Two approaches to identifying risk for abuse and addiction are psychopharmacological challenge studies and neuroimaging experiments. The present study combined these two approaches by examining associations between self-reported euphoria or liking after a dose of d-amphetamine and neural-based responses to anticipation of a monetary reward.

METHODS

Healthy young adults (N = 73) aged 19 and 26, without any history of alcohol/substance dependence completed four laboratory sessions in which they received oral d-amphetamine (20 mg) or placebo, and completed drug effect questionnaires. On a separate session they underwent a functional magnetic resonance imaging scan while they completed a monetary incentive delay task. During the task, we recorded neural signal related to anticipation of winning $5 or $1.50 compared to winning no money (WinMoney-WinZero), in reward related regions.

RESULTS

Liking of amphetamine during the drug sessions was related to differences in activation during the WinMoney-WinZero conditions - in the amygdala (positive), insula (negative) and caudate (negative). In posthoc analyses, liking of amphetamine was also positively correlated with activation of the amygdala during anticipation of large rewards and negatively related to activation of the left insula to both small and large anticipated rewards.

CONCLUSIONS

These findings suggest that individual differences in key regions of the reward network are related to rewarding subjective effects of a stimulant drug. To further clarify these relationships, future pharmacofMRI studies could probe the influence of amphetamine at the neural level during reward anticipation.

Psychotic-like experiences with cannabis use predict cannabis cessation and desire to quit: a cannabis discontinuation hypothesis

BACKGROUND

Evidence suggests that cannabis-induced psychotic-like experiences may be a marker of psychosis proneness. The effect of such experiences on cannabis use has not systematically been examined.

METHODS

We undertook a mixed-methods online survey of 1231 cannabis users (including 926 continued users) using the Cannabis Experiences Questionnaire. We examined the effect of psychotic-like and pleasurable experiences on cessation of cannabis and intention to quit. Socio-demographic variables, cannabis use parameters and substance misuse history were included as covariates. Free-text data explored subjective reasons for changes in use.

RESULTS

Cessation of cannabis use was associated with greater psychotic-like experiences [p < 0.001, Exp(B) 1.262, 95% confidence interval (CI) 1.179-1.351], whilst continued cannabis users were more likely to report pleasurable experiences [p < 0.001, Exp(B) 0.717, 95% CI 0.662-0.776]. Intention to quit cannabis in continued users was associated with greater psychotic-like experiences [p < 0.003, Exp(B) 1.131, 95% CI 1.044-1.225], whilst intention to not quit was significantly associated with increased pleasurable experiences [p < 0.015, Exp(B) 0.892, 95% CI 0.814-0.978]. Whereas former users clearly ascribed cessation to negative experiences, continued users who expressed intention to quit less readily ascribed the intention to negative experiences.

CONCLUSIONS

Elucidation of psychotic-like experiences may form the basis of a therapeutic intervention for those who wish to quit. Cessation in those with cannabis-induced psychotomimetic experiences may offset the risk for the development of a psychotic disorder, in this higher risk group.

Assessing notions of denormalization and renormalization of smoking in light of e-cigarette regulation

The rationale for 'denormalization' of smoking in tobacco policies has been challenged by the emergence of e-cigarettes and the need to regulate e-cigarette use and promotion. Our aim is to assess the research status on e-cigarettes' contribution to 'renormalization' of smoking and to clarify how renormalization of smoking can be appraised at the conceptual and empirical level. Combining conceptual analysis and narrative review, the paper brings out three dimensions of denormalization/renormalization of smoking ('unacceptability/acceptability'; 'invisibility/visibility'; 'phasing out behaviour/maintaining behaviour') and an inherent duality of the e-cigarette as a smoking-like device and a smoking alternative. These analytical dimensions are applied qualitatively to consider the literature identified by searching the Web of Science database for 'e-cigarettes AND renormalization' (and variants thereof). Theoretically, normative changes in smoking acceptability, increased visibility of e-cigarettes and use, and observations of actual use (prevalence, dual use, gateway) can all be applied to illustrate processes of renormalization. However, only acceptability measures and user measures can be said to be empirical tests of renormalization effects. Visibility measures are only based on logical assumptions of a possible renormalization; they are not in themselves indicative of any "real" renormalization effects and can just as well be understood as possible consequences of normalization of e-cigarettes. Just as a downward trend in smoking prevalence is the litmus test of whether denormalization policy works, stagnating or rising smoking prevalence should be the main empirical indicator of renormalization.

The Role of Pleasure Neurobiology and Dopamine in Mental Health Disorders

Recent evidence and research has demonstrated that the pleasure response and associated neurotransmitters and brain circuits play a significant role in substance use disorders (SUDs). It was thought that negative behaviors associated with SUDs resulted from negative choices, but it is now known that chemical changes in the brain drive those behaviors. Several mental health disorders (e.g., eating disorders, non-suicidal self-injury, compulsive sex behaviors, internet gaming, gambling) are also thought to involve those same pleasure responses, neurotransmitters, and brain regions. Studies have shown that the use of naltrexone, a dopamine antagonist, can reduce symptoms of these disorders. It is important for nurses to understand the underlying physiology of mental health disorders that are thought to have an addictive or craving component. This understanding can help reduce stigma. Educating patients about likely neurobiological causes for their disorders can also help reduce guilt and shame. Nurses should educate patients about these disorders and evidence-based treatments, including off-label use of naltrexone. [Journal of Psychosocial Nursing and Mental Health Services, 55(9), 17-21.].

Circuits Regulating Pleasure and Happiness in Bipolar Disorder

According to our model, the motivation for appetitive-searching vs. distress-avoiding behaviors is regulated by two parallel cortico-striato-thalamo-cortical (CSTC) re-entry circuits that include the core and the shell parts of the nucleus accumbens, respectively. An entire series of basal ganglia, running from the caudate nucleus on one side to the centromedial amygdala on the other side, control the intensity of these reward-seeking and misery-fleeing behaviors by stimulating the activity of the (pre)frontal and limbic cortices. Hyperactive motivation to display behavior that potentially results in reward induces feelings of hankering (relief leads to pleasure); while, hyperactive motivation to exhibit behavior related to avoidance of aversive states results in dysphoria (relief leads to happiness). These two systems collaborate in a reciprocal fashion. We hypothesized that the mechanism inducing the switch from bipolar depression to mania is the most essential characteristic of bipolar disorder. This switch is attributed to a dysfunction of the lateral habenula, which regulates the activity of midbrain centers, including the dopaminergic ventral tegmental area (VTA). From an evolutionary perspective, the activity of the lateral habenula should be regulated by the human homolog of the habenula-projecting globus pallidus, which in turn might be directed by the amygdaloid complex and the phylogenetically old part of the limbic cortex. In bipolar disorder, it is possible that the system regulating the activity of this reward-driven behavior is damaged or the interaction between the medial and lateral habenula may be dysfunctional. This may lead to an adverse coupling between the activities of the misery-fleeing and reward-seeking circuits, which results in independently varying activities.

Test-retest reliability of the underlying latent factor structure of alcohol subjective response

RATIONALE

Alcohol subjective experiences are multi-dimensional and demonstrate wide inter-individual variability. Recent efforts have sought to establish a clearer understanding of subjective alcohol responses by identifying core constructs derived from multiple measurement instruments.

OBJECTIVE

The aim of this study was to evaluate the temporal stability of this approach to conceptualizing alcohol subjective experiences across successive alcohol administrations in the same individuals.

METHODS

Healthy moderate alcohol drinkers (n = 104) completed six experimental sessions each, three with alcohol (0.8 g/kg), and three with a non-alcoholic control beverage. Participants reported subjective mood and drug effects using standardized questionnaires before and at repeated times after beverage consumption. We explored the underlying latent structure of subjective responses for all alcohol administrations using exploratory factor analysis and then tested measurement invariance over the three successive administrations using multi-group confirmatory factor analyses.

RESULTS

Exploratory factor analyses on responses to alcohol across all administrations yielded four factors representing "Positive mood," "Sedation," "Stimulation/Euphoria," and "Drug effects and Urges." A confirmatory factor analysis on the separate administrations indicated acceptable configural and metric invariance and moderate scalar invariance.

CONCLUSIONS

In this study, we demonstrate temporal stability of the underlying constructs of subjective alcohol responses derived from factor analysis. These findings strengthen the utility of this approach to conceptualizing subjective alcohol responses especially for use in prospective and longitudinal alcohol challenge studies relating subjective response to alcohol use disorder risk.

Metacognition deficits as a risk factor for prospective motivation deficits in schizophrenia spectrum disorders

Although motivation deficits are key determinants of functional outcomes, little is known about factors that contribute to prospective motivation in people with schizophrenia. One candidate factor is metacognition, or the ability to form complex representations about oneself, others, and the world. This study aimed to assess whether metacognition deficits were a significant predictor of reduced prospective motivation, after controlling for the effects of baseline motivation, anticipatory pleasure, and antipsychotic medication dose. Fifty-one participants with a schizophrenia spectrum disorder completed measures of metacognition and anticipatory pleasure at baseline; participants also completed a measure of motivation at baseline and six months after the initial assessment. Baseline antipsychotic dose was obtained from medical charts. Hierarchical regression analysis revealed that lower levels of baseline metacognition significantly predicted reduced levels of motivation assessed six months later, after controlling for baseline levels of motivation, anticipatory pleasure, and antipsychotic dose. Higher baseline antipsychotic dose was also a significant predictor of reduced six month motivation. Results suggest that metacognition deficits and higher antipsychotic dose may be risk factors for the development of motivation deficits in schizophrenia. Implications include utilizing interventions to improve metacognition in conjunction with evaluating and possibly lowering antipsychotic dose for people struggling with motivation deficits.

Combined Oral Contraceptives and Sexual Function in Women-a Double-Blind, Randomized, Placebo-Controlled Trial

CONTEXT

There is a lack of knowledge about how oral contraceptives may affect sexual function.

OBJECTIVE

To determine whether there is a causal effect of oral contraceptives on sexuality. We hypothesized that a widely used pill impairs sexuality.

DESIGN

A double-blind, randomized, placebo-controlled trial. Enrollment began in February 2012 and was completed in August 2015.

SETTING

Karolinska University Hospital, Stockholm, Sweden.

PARTICIPANTS

A total of 340 healthy women, aged 18-35 years, were randomized to treatment, and 332 completed the study.

INTERVENTIONS

A combined oral contraceptive (150 μg levonorgestrel and 30 μg ethinylestradiol) or placebo for 3 months of treatment.

MAIN OUTCOME MEASURES

The primary outcome was the aggregate score on the Profile of Female Sexual Function (PFSF). Secondary outcomes were the seven domains of the PFSF, the Sexual Activity Log, and the Personal Distress Scale.

RESULTS

Overall sexual function was similar in women in the oral contraceptive and placebo groups. The PFSF domains desire (-4.4; 95% confidence interval [CI], -8.49 to -0.38; P = .032), arousal (-5.1; 95% CI, -9.63 to -0.48; P = .030), and pleasure (-5.1; 95% CI, -9.97 to -0.32; P = .036) were significantly reduced in comparison to placebo, whereas orgasm, concern, responsiveness, and self-image were similar between groups. The mean frequency of satisfying sexual episodes and personal distress were also similar between groups.

CONCLUSIONS

This study shows no negative impact of a levonorgestrel-containing oral contraceptive on overall sexual function, although three of seven sexual function domains were adversely affected.

Pursuing Pleasures of Productivity: University Students' Use of Prescription Stimulants for Enhancement and the Moral Uncertainty of Making Work Fun

This article presents ethnographic data on the use of prescription stimulants for enhancement purposes by university students in New York City. The study shows that students find stimulants a helpful tool in preventing procrastination, particularly in relation to feeling disinterested, overloaded, or insecure. Using stimulants, students seek pleasure in the study situation, for example, to get rid of unpleasant states of mind or intensify an already existing excitement. The article illustrates the notion that enhancement strategies do not only concern productivity in the quantitative sense of bettering results, performances, and opportunities. Students also measure their own success in terms of the qualitative experience of working hard. The article further argues that taking an ethnographic approach facilitates the study of norms in the making, as students experience moral uncertainty-not because they improve study skills and results-but because they enhance the study experience, making work fun. The article thereby seeks to nuance simplistic neoliberal ideas of personhood.

Synthetic cannabis: a comparison of patterns of use and effect profile with natural cannabis in a large global sample

BACKGROUND

The last decade has seen the appearance of myriad novel psychoactive substances with diverse effect profiles. Synthetic cannabinoids are among the most recently identified but least researched of these substances.

METHODS

An anonymous online survey was conducted in 2011 using a quantitative structured research tool. Missing data (median 2%) were treated by available-case analysis.

RESULTS

Of 14,966 participants, 2513 (17%) reported use of synthetic cannabis. Of these, 980 (41% of 2417) reported its use in the last 12 months. Almost all recent synthetic cannabis users (99% of 975) reported ever use of natural cannabis. Synthetic cannabis reportedly had both a shorter duration of action (z=17.82, p<.001) and quicker time to peak onset of effect (z=-9.44, p<.001) than natural cannabis. Natural cannabis was preferred to synthetic cannabis by 93% of users, with natural cannabis rated as having greater pleasurable effects when high (t(930)=-37.1, p<.001, d=-1.22) and being more able to function after use (t(884)=-13.3, p<.001, d=-0.45). Synthetic cannabis was associated with more negative effects (t(859)=18.7, p<.001, d=0.64), hangover effects (t(854)=6.45, p<.001, d=0.22) and greater paranoia (t(889)=7.91, p<.001, d=0.27).

CONCLUSIONS

Users report a strong preference for natural over synthetic cannabis. The latter has a less desirable effect profile. Further research is required to determine longer term consequences of use and comparative dependence potential.

Adaptation, equivalence, and validation of the changes in sexual functioning questionnaire-drugs in a sample of drug-dependent men

This study aimed to adapt and validate the changes in sexual functioning questionnaire-short form in a sample of drug-dependent men, achieving equivalence. Participants were 301 drug-dependent and 202 non-drug-dependent men took part in this study. The analysis of invariance revealed strong factor equivalence (RMSEA = .06; χ2/df = 2.66 and ΔCFI = -.01) for the 4-factor model (desire, pleasure, arousal, and orgasm). This model has shown the best fit indices. No items showed differential item functioning (ΔR (2) Nagelkerke < .035). Reliability ranged from α = 0.83 for pleasure to α = 0.61 for orgasm. A comparison between the scores of control and experimental participants showed significant differences (CI = 99%) in all the dimensions. Thus, a worse sexual functioning has been observed in the drug consumer group. The adaptation of the Changes in Sexual Functioning Questionnaire-short form to drug-dependent individuals showed good psychometric properties.

Interactions of carbon dioxide and food odours in Drosophila: olfactory hedonics and sensory neuron properties

Behavioural responses of animals to volatiles in their environment are generally dependent on context. Most natural odours are mixtures of components that can each induce different behaviours when presented on their own. We have investigated how a complex of two olfactory stimuli is evaluated by Drosophila flies in a free-flying two-trap choice assay and how these stimuli are encoded in olfactory receptor neurons. We first observed that volatiles from apple cider vinegar attracted flies while carbon dioxide (CO2) was avoided, confirming their inherent positive and negative values. In contradiction with previous results obtained from walking flies in a four-field olfactometer, in the present assay the addition of CO2 to vinegar increased rather than decreased the attractiveness of vinegar. This effect was female-specific even though males and females responded similarly to CO2 and vinegar on their own. To test whether the female-specific behavioural response to the mixture correlated with a sexual dimorphism at the peripheral level we recorded from olfactory receptor neurons stimulated with vinegar, CO2 and their combination. Responses to vinegar were obtained from three neuron classes, two of them housed with the CO2-responsive neuron in ab1 sensilla. Sensitivity of these neurons to both CO2 and vinegar per se did not differ between males and females and responses from female neurons did not change when CO2 and vinegar were presented simultaneously. We also found that CO2-sensitive neurons are particularly well adapted to respond rapidly to small concentration changes irrespective of background CO2 levels. The ability to encode temporal properties of stimulations differs considerably between CO2- and vinegar-sensitive neurons. These properties may have important implications for in-flight navigation when rapid responses to fragmented odour plumes are crucial to locate odour sources. However, the flies' sex-specific response to the CO2-vinegar combination and the context-dependent hedonics most likely originate from central rather than peripheral processing.

Effects of modafinil on non-verbal cognition, task enjoyment and creative thinking in healthy volunteers

Background

Modafinil, a putative cognitive enhancing drug, has previously been shown to improve performance of healthy volunteers as well as patients with attention deficit disorder and schizophrenia, mainly in tests of executive functions. The aim of this study was to investigate the effects of modafinil on non-verbal cognitive functions in healthy volunteers, with a particular focus on variations of cognitive load, measures of motivational factors and the effects on creative problem-solving.

Methods

A double-blind placebo-controlled parallel design study evaluated the effect of 200 mg of modafinil (N = 32) or placebo (N = 32) in non-sleep deprived healthy volunteers. Non-verbal tests of divergent and convergent thinking were used to measure creativity. A new measure of task motivation was used, together with more levels of difficulty on neuropsychological tests from the CANTAB battery.

Results

Improvements under modafinil were seen on spatial working memory, planning and decision making at the most difficult levels, as well as visual pattern recognition memory following delay. Subjective ratings of enjoyment of task performance were significantly greater under modafinil compared with placebo, but mood ratings overall were not affected. The effects of modafinil on creativity were inconsistent and did not reach statistical significance.

Conclusions

Modafinil reliably enhanced task enjoyment and performance on several cognitive tests of planning and working memory, but did not improve paired associates learning. The findings confirm that modafinil can enhance aspects of highly demanding cognitive performance in non-sleep deprived individuals.

This article is part of a Special Issue entitled ‘Cognitive Enhancers’.

Cannabinoid facilitation of behavioral and biochemical hedonic taste responses

Cannabinoid receptor agonists are known to stimulate feeding in humans and animals and this effect is thought to be related to an increase in food palatability. On the other hand, highly palatable food stimulates dopamine (DA) transmission in the shell of the nucleus accumbens (NAc) and this effect undergoes one trial habituation. In order to investigate the relationship between the affective properties of tastes and the response of NAc shell DA we studied the effect of delta-9-tetrahydrocannabinol (THC) on behavioral taste reactivity to intraoral infusion of appetitive (sucrose solutions) and aversive (quinine and saturated NaCl solutions) tastes and on the response of in vivo DA transmission in the NAc shell to intraoral sucrose. Rats were implanted with intraoral cannulae and the effect of systemic administration of THC on the behavioral reactions to intraoral infusion of sucrose and of quinine or saturated NaCl solutions were scored. THC increased the hedonic reactions to sucrose but did not affect the aversive reactions to quinine and NaCl. The effects of THC were completely blocked by the CB1 receptor inverse agonist/antagonist rimonabant given at doses that do not affect taste reactivity to sucrose. In rats implanted with microdialysis probes and with intraoral cannulae, THC, made sucrose effective in raising dialysate DA in the shell of the NAc. As in the case of highly palatable food (Fonzies, sweet chocolate), the stimulatory effect of sucrose on shell DA under THC underwent one trial habituation. Altogether, these findings demonstrate that stimulation of CB1 receptors specifically increases the palatability of hedonic taste without affecting that of aversive tastes. Consistent with the ability of THC to increase sucrose palatability is the observation that under THC pretreatment sucrose acquires the ability to induce a release of DA in the shell of the NAc and this property undergoes adaptation after repeated exposure to the taste (habituation). This article is part of a Special Issue entitled 'Central Control of Food Intake'.

Pleasure seeking and birdsong

Songbirds sing at high rates within multiple contexts, suggesting that they are highly motivated to communicate and that the act of singing itself may be rewarding. Little is known about the neural regulation of the motivation to communicate. Dopamine and opioid neuropeptides play a primary role in reward seeking and sensory pleasure. In songbirds, these neurochemicals are found within brain regions implicated in both motivation and reward, including the medial preoptic nucleus (mPOA) and ventral tegmental area (VTA). Several lines of research indicate that dopamine and opioids in these regions play a role in birdsong that differs depending upon whether song is used to attract females (female-directed song) or is not directed towards other individuals (undirected song). Evidence is reviewed supporting the hypotheses: (1) that distinct patterns of dopamine activity influence the motivation to produce undirected and female-directed song, (2) that undirected communication is intrinsically reinforced by immediate release of opioids induced by the act of singing, and (3) that directed communication is socially reinforced by opioids released as part of social interactions.

Phenomenology of adolescent inhalant intoxication

Although volatile substance inhalation is prevalent in many contexts and presents a serious threat to public health, this pernicious form of substance misuse remains poorly understood. The question of why people seek and misuse inhalants may be addressed by examining phenomenological accounts of inhalant intoxication, yet few investigations of inhalant intoxication experiences are reported in the literature. This investigation employed a structured interview to assess inhalant intoxication experiences of 267 low-, moderate-, and high-frequency inhalant users. Low-frequency inhalant users reported predominately hedonic experiences during inhalant intoxication, whereas high-frequency users reported a mixture of hedonic and aversive experiences. Aversive experiences such as depressed mood, suicidal ideation, and chest pain were commonly reported by high-frequency users but were relatively rare among low-frequency users. High-frequency users also experienced significantly more euphoria, talkativeness, and grandiosity during inhalant intoxication than low-frequency users. Hedonic and aversive experiences during episodes of inhalant intoxication are relatively common among high-frequency adolescent inhalant users.

Neonatal maternal separation exacerbates the reward-enhancing effect of acute amphetamine administration and the anhedonic effect of repeated social defeat in adult rats

Early life adversity or parental neglect is linked to the development of a number of psychiatric illnesses, including major depression and substance use disorder. These two disorders are often comorbid and characterized by anhedonia, defined as the reduced ability to experience pleasure or reward. The aim of the present study was to determine the effects of neonatal maternal separation in Long Evans rats, a model of early life stress, on anhedonia under baseline conditions and in response to drug and stress exposure during adulthood. Three hours of daily maternal separation from postnatal day 1 to 14 led to marked decreases in arched-back nursing, licking, and grooming of pups by their dams. In adulthood, brain reward function was assessed using intracranial self-stimulation of the lateral hypothalamus. Lowered current thresholds derived from this procedure are interpreted as reward-enhancing effects, whereas elevations in thresholds are an operational measure of anhedonia. Maternally separated rats did not exhibit anhedonia under baseline conditions compared with non-handled controls but exhibited a greater reward-enhancing effect of acute amphetamine administration. Acute social defeat produced anhedonia in non-handled controls, but not in maternally separated rats. Conversely, control rats habituated to 7 days of repeated social defeat, whereas maternally separated rats developed an increased anhedonic response to the repeated stressor. One week after termination of stress exposure, maternally separated rats still exhibited an increased reward-enhancing effect of acute amphetamine administration compared with non-handled controls, regardless of prior social defeat experience. These data indicate that early life stress increases the reward-enhancing properties of amphetamine, protects against the anhedonic effects of acute stress exposure, and exacerbates the anhedonic response to repeated stress. Thus, early life stress may increase an individual's vulnerability to depressive or addictive disorders when confronted with stress or drug challenge in adulthood.

Acute quetiapine dose-dependently exacerbates anhedonia induced by withdrawal from escalating doses of d-amphetamine

Recent clinical studies show that the atypical antipsychotic medication, quetiapine, may be beneficial in the treatment of substance abuse by alleviating the withdrawal-negative affect stage of addiction. Since the effect of quetiapine on central reward function is largely unknown we studied its effects on brain stimulation reward in animals under withdrawal from escalating doses of d-amphetamine. Male Sprague-Dawley rats were trained to produce an operant response to receive a short train of electrical stimulation to the lateral hypothalamus. Measures of reward threshold were determined with the curve-shift method in different groups of rats before, and during four days after treatment with escalating doses (1 to 10mg/kg, i.p.) of d-amphetamine or its vehicle. At 24h of withdrawal, the effects of two doses of quetiapine (2 and 10mg/kg i.p.) were tested. Animals treated with d-amphetamine showed a 25% reward deficit at 24h of withdrawal, an effect that decreased progressively over the next three days. Quetiapine attenuated reward in the vehicle-control animals, and amplified the anhedonia at the moderate, but not the low, dose in the animals under withdrawal. These results show that acute treatment with clinically relevant doses of quetiapine for the treatment of schizophrenia may exacerbate anhedonia induced by amphetamine withdrawal. Further research should investigate whether repeated treatment with quetiapine has the ability to reverse amphetamine withdrawal-induced anhedonia.

Altered neural response of the appetitive emotional system in cocaine addiction: an fMRI Study

Research on addiction suggests that emotional alterations play an essential role in the development, maintenance, relapse and treatment outcome of substance abuse disorders. Although many neuroimaging studies focussed on the neural response to conditioned stimuli, much less is known about the neural response to natural affective stimuli in this pathological population. Previous research has demonstrated an altered emotional experience and autonomic response to emotional stimuli using the International Affective Picture System (IAPS) in drug abusers. Here we aimed, using functional magnetic resonance imaging (fMRI), to study the alterations in the neural responsitivity to pleasant (erotic), unpleasant and neutral IAPS stimuli in cocaine addiction. Thirty-two cocaine-dependent subjects and 26 matched controls completed an fMRI session during the presentation of a set of IAPS pictures as background, while performing a letter discrimination task. Consistent with previous studies, emotional pictures activated an emotional network including amygdala, medial prefrontal cortex, orbitofrontal cortex and occipito-temporal areas in both groups. However, compared with controls, the cocaine group showed a significant hypoactivation of the dorsal and ventral striatum (including the nucleus accumbens), thalamus, parietal cortex and dorso-medial prefrontal cortex (dmPFC) when processing pleasant pictures. The analysis of pleasant versus unpleasant stimuli suggested that between-group differences in the dmPFC and striatal activation may be attributed to arousal processing rather than valence. These results could reflect the neural basis for the reduced ability of cocaine-dependent subjects to experience pleasure by daily natural reinforcers, suggesting that these alterations in the emotion processing may play an important role in drug dependence, treatment and relapse.

Dopamine enhances expectation of pleasure in humans

Human action is strongly influenced by expectations of pleasure. Making decisions, ranging from which products to buy to which job offer to accept, requires an estimation of how good (or bad) the likely outcomes will make us feel [1]. Yet, little is known about the biological basis of subjective estimations of future hedonic reactions. Here, we show that administration of a drug that enhances dopaminergic function (dihydroxy-L-phenylalanine; L-DOPA) during the imaginative construction of positive future life events subsequently enhances estimates of the hedonic pleasure to be derived from these same events. These findings provide the first direct evidence for the role of dopamine in the modulation of subjective hedonic expectations in humans.