Relationship between cortisol and serotonin metabolites and transporters in alcoholism [correction of alcolholism]

Salivary cortisol awakening levels are reduced in human subjects with intermittent explosive disorder compared with controls

BACKGROUND

The role of the hypothalamic-pituitary-adrenal (HPA) axis in human aggressive behavior is poorly characterized, though some studies report that, unlike depression, circulating or salivary levels of cortisol are low compared with controls.

METHODS

In this study, we collected three salivary cortisol levels (two in the morning and one in the evening) on three separate days in 78 adult study participants with (n = 28) and without (n = 52) prominent histories of impulsive aggressive behavior. Plasma C-Reactive Protein (CRP) and Interleukin-6 (IL-6) were also collected in most study participants. Aggressive study participants meet DSM-5 criteria for Intermittent Explosive Disorder (IED) while non-aggressive participants either had a history of a psychiatric disorder or no such history (Controls).

RESULTS

Morning, but not evening, salivary cortisol levels were significantly lower in IED (p < 0.05), compared with control, study participants. In addition, salivary cortisol levels correlated with measures of trait anger (partial r = -0.26, p < 0.05) and aggression (partial r = -0.25, p < 0.05) but not with measures of impulsivity, psychopathy, depression, history of childhood maltreatment, or other tested variables that often differ in individuals with IED. Finally, plasma CRP levels correlated inversely with morning salivary cortisol levels (partial r = -0.28, p < 0.05); plasma IL-6 levels showed a similar, though not statistically significant (rp = -0.20, p = 0.12) relationship with morning salivary cortisol levels.

CONCLUSION

The cortisol awakening response appears to be lower in individuals with IED compared with controls. In all study participants, morning salivary cortisol levels correlated inversely with trait anger, trait aggression, and plasma CRP, a marker of systemic inflammation. This suggests the present of a complex interaction between chronic-low level inflammation, the HPA axis, and IED that warrants further investigation.

The effects of social isolation stress and discrimination on mental health

Social isolation and discrimination are growing public health concerns associated with poor physical and mental health. They are risk factors for increased morbidity and mortality and reduced quality of life. Despite their detrimental effects on health, there is a lack of knowledge regarding translation across the domains of experimental research, clinical studies, and real-life applications. Here, we review and synthesize evidence from basic research in animals and humans to clinical translation and interventions. Animal models indicate that social separation stress, particularly in early life, activates the hypothalamic-pituitary-adrenal axis and interacts with monoaminergic, glutamatergic, and GABAergic neurotransmitter systems, inducing long-lasting reductions in serotonin turnover and alterations in dopamine receptor sensitivity. These findings are of particular importance for human social isolation stress, as effects of social isolation stress on the same neurotransmitter systems have been implicated in addictive, psychotic, and affective disorders. Children may be particularly vulnerable due to lasting effects of social isolation and discrimination stress on the developing brain. The effects of social isolation and loneliness are pronounced in the context of social exclusion due to discrimination and racism, during widespread infectious disease related containment strategies such as quarantine, and in older persons due to sociodemographic changes. This highlights the importance of new strategies for social inclusion and outreach, including gender, culture, and socially sensitive telemedicine and digital interventions for mental health care.

Alcohol-related phenotypes and platelet serotonin concentration

Alcohol dependence is a chronic relapsing mental disorder with heterogeneous and complex underlying biology. It is frequently associated with nicotine dependence, severity of alcohol dependence symptoms, and diverse alcohol-related phenotypes, including the presence of delirium tremens and withdrawal symptoms, early or late onset of alcohol abuse, aggression, suicidal behavior, and anxiety. While searching for peripheral biomarkers of altered serotonergic (5-HT) function in alcohol dependence and alcohol-related behaviors, we determined a peripheral biomarker, i.e., platelet 5-HT concentration in a large group of Caucasian subjects with alcohol dependence subdivided according to the presence of specific alcohol-related phenotypes and smoking status. Individuals with alcohol dependence (n = 661) of both sexes were evaluated using Structural Clinical Interview based on DSM-IV criteria, while platelet 5-HT concentration was determined using the spectrophotofluorimetric method. Smoking is significantly associated, while sex and age are not, with platelet 5-HT concentration. Severe alcohol dependence and lack of withdrawal symptoms were associated with significantly decreased platelet 5-HT concentration in alcohol-dependent non-smokers. In smokers, significantly lower platelet 5-HT concentration was found in patients with the late onset of alcohol abuse. These results suggested that platelet 5-HT concentration might be used as a peripheral marker of different alcohol-related phenotypes, after controlling for the effects of smoking and sex.

Magnitude of psychiatric comorbidity in patients with obesity in Northern Indian population

BACKGROUND AND AIMS

To determine the prevalence of different psychiatric comorbidities in patients with obesity and study their relationship with the degrees of obesity.

METHODS

This cross-sectional study included 151 patients with a BMI≥25 kg/m². Subjects with diagnosed psychiatric illness, type 2 diabetes mellitus, coronary artery disease or any neurological illness were excluded. Prevalence of psychiatric comorbidities was assessed by MINI screening tool for all major axis 1 disorders including anxiety, eating and mood disorders. The WHOQOL-BREF was used for assessment of well-being, in the four domains, physical, psychological, social and environmental.

RESULTS

Females constituted 68.6% of the study population. Lifetime diagnosis of any psychiatric illness was present in 24%, higher in females than males [31% vs 9%, p = 0.003]. The WHOQOL-BREF average scores of psychological, physical and environmental domains were significantly lower (p < 0.001) in patients diagnosed with depression as compared to those without. The WHOQOL-BREF average score of only the physical domain were significantly lower in individuals with BMI ≥30 kg/m² as compared to those with BMI <30 kg/m².

CONCLUSIONS

The burden of undiagnosed psychiatric comorbidity in patients with obesity decreases the quality of life. There is need to screen for psychiatric comorbidities for effective management of obesity.

Neuroticism Associates with Cerebral in Vivo Serotonin Transporter Binding Differently in Males and Females

BACKGROUND

Neuroticism is a major risk factor for affective disorders. This personality trait has been hypothesized to associate with synaptic availability of the serotonin transporter, which critically controls serotonergic tone in the brain. However, earlier studies linking neuroticism and serotonin transporter have failed to produce converging findings. Because sex affects both the serotonergic system and the risk that neuroticism poses to the individual, sex may modify the association between neuroticism and serotonin transporter, but this question has not been investigated by previous studies.

METHODS

Here, we combined data from 4 different positron emission tomography imaging centers to address whether neuroticism is related to serotonin transporter binding in vivo. The data set included serotonin transporter binding potential values from the thalamus and striatum and personality scores from 91 healthy males and 56 healthy females. We specifically tested if the association between neuroticism and serotonin transporter is different in females and males.

RESULTS

We found that neuroticism and thalamic serotonin transporter binding potentials were associated in both males and females, but with opposite directionality. Higher neuroticism associated with higher serotonin transporter binding potential in males (standardized beta 0.292, P=.008), whereas in females, higher neuroticism associated with lower serotonin transporter binding potential (standardized beta -0.288, P=.014).

CONCLUSIONS

The finding is in agreement with recent studies showing that the serotonergic system is involved in affective disorders differently in males and females and suggests that contribution of thalamic serotonin transporter to the risk of affective disorders depends on sex.

[DSM-5: important changes in the field of addictive diseases]

There are two major changes in the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) concerning the field of addiction. Firstly, the previous distinction between abuse and dependence has been abolished and both disorders are now subsumed under the category addiction and related disorders. Secondly, pathological gambling has now been included in the section of addiction with slight changes in diagnostic criteria. Both changes have major implications for the definition and conceptualization of what we call a psychiatric "disease" or "disorder", which have also been addressed in the introductory statement of DSM-5. Concerning the category of abuse that is now part of substance use disorders, there is a concern that a well-defined disorder ("dependence") is now mixed with a less well-defined syndrome ("abuse"). The inclusion of non-substance, behavioral addictions poses the danger of pathologizing a wide range of human behavior in future revisions of the classification. Both concerns are further addressed in this article.

Molecular imaging in alcohol dependence

The cellular mechanisms of alcohol's effects in the brain are complex, targeting multiple transmitter systems. Molecular imaging has been used to study the effects of alcohol and alcohol use disorders on these various systems. Studies of dopaminergic indices have provided robust evidence for deficits in D2-mediated transmission in the striatum of chronic recently detoxified alcoholics. Their presence in the at-risk state prior to excessive drinking, and their recovery after long-term sobriety, are unclear and represent an active area of current research. Investigations of the GABAergic system have shown generalized deficits in various brain regions in the chronic abstinence phase. Studies of the opiate system have suggested alterations in some subtypes in discrete brain regions, including the ventral striatum, while studies of serotonin have been negative and those of the cannabinoid system have been inconclusive. Future investigations should target the glutamatergic system, which plays an important role both in the acute intoxicating effects of alcohol as well as in the long-term effects associated with dependence.

How the cerebral serotonin homeostasis predicts environmental changes: a model to explain seasonal changes of brain 5-HTT as intermediate phenotype of the 5-HTTLPR

Molecular imaging studies with positron emission tomography have revealed that the availability of serotonin transporter (5-HTT) in the human brain fluctuates over the course of the year. This effect is most pronounced in carriers of the short allele of the 5-HTT promoter region (5-HTTLPR), which has in several previous studies been linked to an increased risk to develop mood disorders. We argue that long-lasting fluctuations in the cerebral serotonin transmission, which is regulated via the 5-HTT, are responsible for mediating responses to environmental changes based on an assessment of the expected "safety" of the environment; this response is obtained in part through serotonergic modulation of the hypothalamic-pituitary-adrenal (HPA) axis. We posit that the intermediate phenotype of the s-allele may properly be understood as mediating a trade-off, wherein increased responsiveness of cerebral serotonin transmission to seasonal and other forms of environmental change imparts greater behavioral flexibility, at the expense of increased vulnerability to stress. This model may explain the somewhat higher prevalence of the s-allele in some human populations dwelling at geographic latitudes with pronounced seasonal climatic changes, while this hypothesis does not rule out that genetic drift plays an additional or even exclusive role. We argue that s-allele manifests as an intermediate phenotype in terms of an increased responsiveness of the 5-HTT expression to number of daylight hours, which may serve as a stable surrogate marker of other environmental factors, such as availability of food and safety of the environment in populations that live closer to the geographic poles.

Wege aus der Abhängigkeit

Hintergrund: Alkohol-assoziierte Reize lösen bei alkoholabhängigen Patienten konditionierte Reaktionen aus, die zu einer erhöhten Motivation der Alkoholeinnahme führen können. Klassische Konditionierungsprozesse scheinen demnach sowohl zur Aufrechterhaltung der Abhängigkeit als auch zum Rückfallgeschehen nach Entzug beizutragen. Bildgebende Studien weisen darauf hin, dass das dopaminerge Neurotransmittersystem an assoziativen Lernvorgängen beteiligt ist und Veränderungen innerhalb dieses Systems bei entgifteten alkoholabhängigen Patienten zum Rückfall beitragen könnten. Die genauen Mechanismen in diesem Zusammenhang sind bisher jedoch ungeklärt. Zielsetzung: Ziel dieser Arbeit ist die Darstellung von motivationalen Veränderungen und deren (neuroadaptiven) Grundlagen bei Alkoholabhängigkeit. Ein genaueres Verständnis davon, welche neuronalen und motivationalen Prozesse im Rahmen des Rückfallgeschehens eine Rolle spielen, könnte sowohl pharmakologische als auch therapeutische Implikationen für die Behandlung der Alkoholabhängigkeit liefern. Methodik: Diese Arbeit umfasst eine Literaturanalyse über neuroadaptive Veränderungen bei Alkoholabhängigkeit mit besonderem Fokus auf Lernprozesse und deren Rolle beim Rückfallgeschehen. Die Literaturrecherche basiert auf Recherchen der Forschergruppe 1617 der Deutschen Forschungsgesellschaft (DFG; Learning and Habitization in Alcohol Dependence, LeAD). Schlussfolgerung: Bisher existieren keine Untersuchungen, in denen neuroadaptive Veränderungen der Alkoholabhängigkeit mit spezifischen Lerndefiziten in Zusammenhang gebracht werden. Die DFG Forschergruppe LeAD untersucht neuronale Korrelate von lernbezogenen Rückfallprädiktoren. Ein Ziel dieser Untersuchung ist es herauszufinden, warum alkoholabhängige Patienten nach ihrer Entgiftung oft nicht lernen, Alkohol durch alternative belohnende Reize und Situation zu ersetzen und welche neuronalen Grundlagen diesem Defizit zu Grunde liegen.

Neurobiology of addiction: insight from neurochemical imaging

Neuroimaging studies have been crucial in understanding changes in the various neurotransmitter systems implicated in addiction in the living human brain. Predominantly reduced striatal dopamine transmission appears to play an important role in psychostimulant, alcohol and heroin addiction, while addiction to cannabis may be mediated primarily by the endocannabinoid system. However, the study of other neurotransmitter systems likely involved in addiction, for example glutamate, has been limited by the number and quality of available radiotracers, and data on changes in these systems in the most common addictions are emerging only now. Further studies are needed to understand fully how the interplay of various neurotransmitter systems contributes to addiction and to ultimately help to develop more effective treatment approaches.

Major depressive disorders in chronic hemodialysis patients in Nazareth: identification and assessment

OBJECTIVE

Depression illnesses are commonly observed in hemodialysis (HD) patients, which can influence the quality of life of end-stage renal disease patients. We evaluate the prevalence and predictive risk factors of depression in the Arab population undergoing HD in Nazareth, Israel.

METHODS

We conducted a prospective study that included 71 patients in the HD unit with a mean age of 61.9 ± 14.13 years who had undergone HD and 26 healthy control subjects with a mean age of 59.3 ± 7.3. Beck's Depression Inventory and Hamilton Depression Scale assessments were administered. Blood analysis for hematological and biochemical parameters was obtained. Diagnosis was made using the Diagnostic and Statistical Manual of Mental Disorders scale to correlate psychological variables with clinical, hematological, and biochemical parameters. Statistical analysis was carried out using analysis of variance followed by Tukey post-hoc multiple comparison tests.

RESULTS

The prevalence of depression was 43.7% in HD patients. Between HD patients and controls, cortisol values were 16.96 ± 0.5476 and 11.96 ± 1.116, respectively (P < 0.0001; 95% confidence intervals [CI]: 2.416-6.825). Between depressed HD patients versus control subjects, cortisol values were 16.48 ± 0.72 and 11.96 ± 1.116, respectively (P = 0.0013; 95% CI: 1.878-7.184). Hematological and biochemical parameters were compared between depressed HD and nondepressed patients, but differences between the two groups were found to be insignificant (P > 0.05).

CONCLUSION

Our HD patients were severely depressed. Studies of glucocorticoid turnover activity such as cortisol, a potent chemical stress hormone, may be used as a model and marker for early diagnosis of depression among HD patients. The strong familial support system in Arabic traditions has failed to decrease depression among these patients.

Central serotonin transporter levels are associated with stress hormone response and anxiety

RATIONALE

Negative mood states are characterized by both stress hormone dysregulation and serotonergic dysfunction, reflected by altered thalamic serotonin transporter (5-HTT) levels. However, so far, no study examined the individual association between cortisol response and cerebral in vivo 5-HTT levels in patients suffering from negative mood states.

OBJECTIVE

The objective of this cross-sectional study was to assess the interrelation of cortisol response, thalamic 5-HTT levels, and anxiety in healthy subjects and two previously published samples of patients with unipolar major depression (UMD) and obsessive-compulsive disorder (OCD), controlling for age, gender, 5-HTT genotype, smoking, and seasonality.

METHODS

Regional 5-HTT levels and cortisol response to dexamethasone-corticotropin (Dex-CRH) challenge were assessed in consecutive samples of medication-free patients suffering from UMD (N = 10) and OCD (N = 10), and 20 healthy volunteers. The intervention used was combined Dex-CRH test and [(11)C]DASB positron emission tomography. The main outcome measures were: 5-HTT binding potential (BP(ND)) in a predefined thalamic ROI, cortisol response defined as the maximum cortisol increase in the combined Dex-CRH-test, and state of anxiety from the state-trait-anxiety inventory.

RESULTS

Reduced thalamic 5-HTT BP(ND) was associated with increased cortisol response (r = -0.35, p < 0.05; in patients: r = -0.53, p < 0.01) and with increased state anxiety (r = -0.46, p < 0.01), surviving correction for age, gender, 5-HTT genotype, smoking, and seasonality (p < 0.05). The 5-HTT genotype, on the contrary, was not significantly associated with cortisol response (p = 0.19) or negative mood (p = 0.23).

CONCLUSION

The association between stress hormone response, thalamic 5-HTT levels, and anxiety in patients suffering from negative mood states suggests an interaction between two major mechanisms implicated in negative mood states in humans.

Role of the serotonergic system in alcohol dependence: from animal models to clinics

Alcohol dependence remains among the most common substance abuse problems worldwide, and compulsive alcohol consumption is a significant public health concern. Alcohol is an addictive drug that alters brain function through interactions with multiple neurotransmitter systems. These neurotransmitter systems mediate the reinforcing effects of alcohol. Specifically, the serotonergic system is important in mediating alcohol reward, preference, dependence, and craving. In this review chapter, we first discuss the serotonin system as it relates to alcoholism, and then outline interactions between this system and other neurotransmitter systems. We emphasize the serotonin transporter and its possible role in alcoholism, then present several serotonergic receptors and discuss their contribution to alcoholism, and finally assess the serotonin system as a target for pharmacotherapy, with an emphasis on current and potential treatments.

Impact of psychosocial adversity on alcohol intake in young adults: moderation by the LL genotype of the serotonin transporter polymorphism

BACKGROUND

Evidence from animal studies supports a role for serotonin transporter gene promoter polymorphism (5-HTTLPR) gene-environment interaction (G x E) in the development of excessive alcohol intake. Few studies in humans have been conducted on this topic, yielding inconsistent results. The present study aims to further explore G x E between 5-HTTLPR and exposure to psychosocial adversity on alcohol consumption in a high-risk community sample of young adults.

METHODS

Data were collected as part of the Mannheim Study of Children at Risk, an ongoing epidemiological cohort study following the outcome of early risk factors from birth into young adulthood. At age 19 years, 309 participants (142 male participants, 167 female participants) were genotyped for the biallelic and triallelic 5-HTTLPR and were administered a 45-day alcohol timeline follow-back interview, providing measures of the total number of drinks and the number of binge drinking days. Psychosocial adversity was assessed at birth (family adversity) and at age 19 (negative life events).

RESULTS

In contrast to various previous reports, a significant G x E emerged, indicating that, when exposed to high psychosocial adversity, individuals with the LL genotype of 5-HTTLPR exhibited more hazardous drinking than those carrying the S allele or those without exposure to adversity. This effect, which was confined to male participants, held both for different classifications of 5-HTTLPR and different types of adversity.

CONCLUSIONS

One explanation for the discrepant results might be heterogeneity in alcohol phenotypes. While the L allele relates more strongly to early-onset alcoholism, the S allele may be linked more closely to alcohol use associated with anxiety and depression.

Gamma-Hydroxybutyrate Reduces both Withdrawal Syndrome and Hypercortisolism in Severe Abstinent Alcoholics: An Open Study vs. Diazepam

In 42 alcoholic inpatients we performed an open randomized study to compare the effects of diazepam and gamma-hydroxybutyrate (GHB) on the suppression of severe alcohol withdrawal syndrome and hypercortisolism. Both diazepam (.5 mg/kg bodyweight, q.i.d.) and GHB (50 mg/kg bodyweight, q.i.d.) were orally administered for three weeks. During all study period, GHB was more able than diazepam in reducing both withdrawal syndrome and hypercortisolism. These effects were evident during the first week of treatment and persisted throughout the study period. The results confirm a strict correlation between high levels of plasma cortisol and alcohol withdrawal symptoms and they show a slight superiority of GHB over diazepam in the suppression of both ethanol withdrawal and hypercortisolism. Taken together, our data suggest that GHB may act as potent anti-withdrawal agent in severe abstinent alcoholics.

Positron emission tomography imaging of the serotonin transporter and 5-HT(1A) receptor in alcohol dependence

BACKGROUND

Rodent models as well as studies in humans have suggested alterations in serotonin (5-HT) innervation and transmission in early-onset genetically determined or type II alcoholism. This study examines two indices of serotonergic transmission, 5-HT transporter levels and 5-HT(1A) availability, in vivo, in type II alcoholism. This is the first report of combined tracers for pre- and postsynaptic serotonergic transmission in the same alcoholic subjects and the first study of 5-HT(1A) receptors in alcoholism.

METHODS

Fourteen alcohol-dependent subjects were scanned (11 with both tracers, 1 with [(11)C]DASB only, and two with [(11)C]WAY100635 only). Twelve healthy control subjects (HC) subjects were scanned with [(11)C]DASB, and another 13 were scanned with [(11)C]WAY100635. Binding potential (BP(p), mL/cm(3)) and the specific to nonspecific partition coefficient (BP(ND), unitless) were derived for both tracers using a two-tissue compartment model and compared with control subjects across different brain regions. Relationships to severity of alcoholism were assessed.

RESULTS

No significant differences were observed in regional BP(p) or BP(ND) between patients and control subjects in any of the regions examined. No significant relationships were observed between regional 5-HT transporter availability, 5-HT(1A) availability, and disease severity, with the exception of a significant negative correlation between 5-HT transporters and years of dependence in amygdala and insula.

CONCLUSION

This study did not find alterations in measures of 5-HT(1A) or 5-HT transporter levels in patients with type II alcoholism.

Serotonergic function, two-mode models of self-regulation, and vulnerability to depression: what depression has in common with impulsive aggression

Evidence from diverse literatures supports the viewpoint that two modes of self-regulation exist, a lower-order system that responds quickly to associative cues of the moment and a higher-order system that responds more reflectively and planfully; that low serotonergic function is linked to relative dominance of the lower-order system; that how dominance of the lower-order system is manifested depends on additional variables; and that low serotonergic function therefore can promote behavioral patterns as divergent as impulsive aggression and lethargic depression. Literatures reviewed include work on two-mode models; studies of brain function supporting the biological plausibility of the two-mode view and the involvement of serotonergic pathways in functions pertaining to it; and studies relating low serotonergic function to impulsiveness, aggression (including extreme violence), aspects of personality, and depression vulnerability. Substantial differences between depression and other phenomena reviewed are interpreted by proposing that depression reflects both low serotonergic function and low reward sensitivity. The article closes with brief consideration of the idea that low serotonergic function relates to even more diverse phenomena, whose natures depend in part on sensitivities of other systems.

Relationship of the serotonin transporter with prolactin response to meta-chlorophenylpiperazine in cocaine dependence

BACKGROUND

Preclinical evidence indicates that exposure to cocaine influences the activity of the serotonin transporter (5-HTT) as well as several 5-HT receptor subtypes. However, little is known about the relationship between the 5-HTT and 5-HT receptors following cocaine exposure in humans.

OBJECTIVE

We examined the relationship between platelet 5-HTT, a presynaptic 5-HT measure, and prolactin (PRL) response to meta-chlorophenylpiperazine (m-CPP), a postsynaptic 5-HT receptor agonist in cocaine dependent individuals.

METHODS

Platelet [3H] paroxetine binding sites were assayed and the m-CPP challenge test was performed in 35 African American cocaine dependent individuals and 33 controls. Clinical measures included assessments of drug use severity and depression.

RESULTS

Cocaine subjects showed reduced Bmax of [3H] paroxetine (t=4.67, p<0.01) and blunted PRL response to m-CPP (F=21.86, p<0.01) compared to controls. There was a positive correlation between Bmax and delta PRL [peak-baseline PRL] in cocaine subjects (r=0.50, p<0.01) but not in controls (r=0.19). ANCOVA analyses showed that the cocaine subgroup with moderate and severe reduction in Bmax showed a greater blunting in PRL response compared to the subgroup with mild Bmax reductions (F=9.44, p<.005). Multivariate regression models showed that the main effects as well as the interaction of Bmax and severity of cocaine use significantly contributed to impaired PRL response (F=17.90, p<.001).

CONCLUSIONS

Disturbances in serotonin transporter binding and post-synaptic 5-HT receptor function seem to be associated in cocaine-dependent subjects. Severity of cocaine use appears to mediate this relationship. Whether there is a causal association between the two measures, or cocaine has separate and independent pre- and post-synaptic effects needs to be clarified.

Behavioral characteristics and neurobiological substrates shared by Pavlovian sign-tracking and drug abuse

Drug abuse researchers have noted striking similarities between behaviors elicited by Pavlovian sign-tracking procedures and prominent symptoms of drug abuse. In Pavlovian sign-tracking procedures, repeated paired presentations of a small object (conditioned stimulus, CS) with a reward (unconditioned stimulus, US) elicits a conditioned response (CR) that typically consists of approaching the CS, contacting the CS, and expressing consummatory responses at the CS. Sign-tracking CR performance is poorly controlled and exhibits spontaneous recovery and long-term retention, effects that resemble relapse. Sign-tracking resembles psychomotor activation, a syndrome of behavioral responses evoked by addictive drugs, and the effects of sign-tracking on corticosterone levels and activation of dopamine pathways resemble the neurobiological effects of abused drugs. Finally, the neurobiological profile of individuals susceptible to sign-tracking resembles the pathophysiological profile of vulnerability to drug abuse, and vulnerability to sign-tracking predicts vulnerability to impulsive responding and alcohol self-administration. Implications of sign-tracking for models of drug addiction are considered.

Anxiety is associated with reduced central serotonin transporter availability in unmedicated patients with unipolar major depression: a [11C]DASB PET study

Serotonergic dysfunction may contribute to negative mood states in affective disorders. Some in vivo imaging studies showed reduced availability of serotonin transporters (5-HTT) in the brainstem and thalamus of patients with major depression. We tested the hypothesis that 5-HTT availability is reduced in unmedicated unipolar patients with major depression compared to healthy control subjects matched for gender, age, genotype and smoking status. Availability of 5-HTT was measured in vivo with positron emission tomography and [(11)C]-3-amino-4-(2-dimethylaminomethyl-phenylsulfanyl)-benzonitrile (DASB) in the midbrain, thalamus and amygdala. DASB binding was correlated with the severity of depression (Beck's Depression Inventory), anxiety (Spielberger's State-Trait Anxiety Inventory) and personality traits (Temperament and Character Inventory). Patients with major depression displayed reduced 5-HTT availability in the thalamus (P=0.005). In patients, low serotonin transporter availability correlated with high anxiety (thalamus: r=-0.78, P=0.004; midbrain: r=-0.78, P=0.004; amygdala: r=-0.80, P=0.003). Correlations with severity of depression were weaker and did not survive correction for multiple testing. These results support the hypothesis that central serotonergic dysfunction is associated with negative mood states in affective disorders. In the thalamus, a low serotonin reuptake capacity may interfere with thalamic control of cortical excitability and contribute to anxiety rather than depression per se in major depression.

Imaging the neurochemistry of alcohol and substance abuse

Animal models of abuse and dependence have long suggested that chronic drug and alcohol exposure is associated with marked changes in neurochemistry. The development of PET and SPECT imaging now allows investigation of the effects of addiction on the neurochemistry of the human brain. This article reviews the literature of radiochemical imaging in cocaine, alcohol, heroin, methamphetamine, MDMA, and ketamine abuse and dependence.

Monoamine metabolites level in CSF is related to the 5-HTT gene polymorphism in treatment-resistant depression

The serotonin (5-hydroxytryptamine) transporter (5-HTT) is considered to affect the pathogenesis of mood disorders. Large number of genetic association studies between 5-HTT functional polymorphisms and vulnerability of mood disorders and therapeutic response to antidepressants has been carried out. We investigated the influence of 5-HTT-linked polymorphic region (5-HTTLPR) and 5-HTT 17 bp variable number of tandem repeat polymorphism (5-HTTVNTR) polymorphisms on concentrations of monoamine metabolites in cerebrospinal fluid (CSF) among treatment-resistant patients with mood disorders. Subjects were 119 Swedish patients with persistent mood disorders and 141 healthy subjects. In 112 of these patients, we measured 5-hydroxyindoleacetic acid (5-HIAA), homovanillic acid (HVA), and 3-methoxy-4-hydroxyphenylglycol in CSF. Genotyping for 5-HTT polymorphisms from genomic DNA was carried out by PCR. There was no significant difference in allele/genotype frequency between patients and healthy subjects. In patients with mood disorders, we found significant difference in mean 5-HIAA concentration between 5-HTTLPR genotypes (p=0.03). Although the 5-HIAA concentration showed a tendency to be higher in short (S) carriers than in non-S carriers of the 5-HTTLPR in patients (p=0.06), when considering patients with major depressive disorder (MDD), the 5-HIAA concentration was significantly higher among S carriers than among non-S carriers (p=0.02). Moreover, the 5-HIAA concentration was higher in S/S subjects compared to long (L)/L (p=0.0001) and L/S (p=0.002) subjects in patients with MDD. Similarly, there was higher HVA concentration in S/S subjects compared to L/L (p=0.002) and L/S subjects (p=0.002). There was no effect of 5-HTTVNTR. Our findings show that the 5-HTTLPR polymorphism affects 5-HIAA and HVA concentrations among treatment-resistant patients with mood disorders.

Positron emission tomography study of regional brain metabolic responses to a serotonergic challenge in major depressive disorder with and without comorbid lifetime alcohol dependence

This is the first study contrasting regional glucose metabolic rate (rCMRglu) responses to a serotonergic challenge in major depressive disorder (MDD) with and without comorbid alcohol dependence. In a university hospital, patients with MDD without a history of alcohol dependence (MDD only) and patients with MDD and comorbid alcohol dependence (MDD/ALC) were enrolled in this study. Subjects with comorbid borderline personality disorder were excluded. A bolus injection of approximately 5 mCi of (18)fluorodeoxyglucose was administered 3 h after the administration of placebo or fenfluramine. We found an anterior medial prefrontal cortical area where MDD/ALC subjects had more severe hypofrontality than MDD only patients. This area encompassed the left medial frontal and left and right anterior cingulate gyri. This group difference disappeared after fenfluramine administration. The fact that the observed group difference disappeared after the fenfluramine challenge suggests that serotonergic mechanisms play a role in the observed differences between the groups.

Reduced availability of serotonin transporters in obsessive-compulsive disorder correlates with symptom severity - a [11C]DASB PET study

Reduced availability of brainstem serotonin transporters (5-HTT) has been observed in vivo in obsessive-compulsive disorder (OCD). However, results vary and may be influenced by competition with endogenous serotonin. Using positron emission tomography (PET) and [11C]DASB, a specific 5-HTT ligand that showed no competition with serotonin for 5-HTT binding in vitro, we tested the hypothesis that 5-HTT availability is reduced in OCD patients and correlated with OCD severity. METHODS. 5-HTT availability in the thalamus and the midbrain was measured in nine drug-free OCD patients and compared with 19 healthy controls, matched for the individual combination of 5-HTT genotype, gender and smoking status. OCD severity was assessed with the Yale-Brown obsessive compulsive scale (Y-BOCS). RESULTS. 5-HTT availability was significantly reduced in the thalamus and midbrain of OCD patients. Age and 5-HTT in the thalamus explained 83% of OCD severity in patients that were drug-free for at least 1 year. CONCLUSION. This PET study confirms a central role of the serotonergic system, particularly the thalamus in the pathogenesis of obsessive compulsive disorder.

Developmental imaging genetics: challenges and promises for translational research

Advances in molecular biology, neuroimaging, genetic epidemiology, and developmental psychopathology have provided a unique opportunity to explore the interplay of genes, brain, and behavior within a translational research framework. Herein, we begin by outlining an experimental strategy by which genetic effects on brain function can be explored using neuroimaging, namely, imaging genetics. We next describe some major findings in imaging genetics to highlight the effectiveness of this strategy for delineating biological pathways and mechanisms by which individual differences in brain function emerge and potentially bias behavior and risk for psychiatric illness. We then discuss the importance of applying imaging genetics to the study of psychopathology within a developmental framework. By beginning to move toward a systems-level approach to understanding pathways to behavioral outcomes as they are expressed across development, it is anticipated that we will move closer to understanding the complexities of the specific mechanisms involved in the etiology of psychiatric disease. Despite the numerous challenges that lie ahead, we believe that developmental imaging genetics has potential to yield highly informative results that will ultimately translate into public health benefits. We attempt to set out guidelines and provide exemplars that may help in designing fruitful translational research applications that incorporate a developmental imaging genetics strategy.

PET [11C]DASB Imaging of Serotonin Transporters in Patients with Alcoholism

OBJECTIVE

Alcoholism and aggression have each been associated with neurochemical measurements suggestive of decreased serotonin synaptic transmission. We measured densities of the serotonin transporter (SERT) in a moderate-sized sample of alcoholic patients who were assessed for aggressive characteristics.

METHODS

Thirty alcoholic inpatients and 18 healthy controls received a PET scan with [(11)C]-3-amino-4-(2-dimethylaminomethylphenylsulfanyl)-benzonitrile. The alcoholic inpatients were classified as aggressive or nonaggressive based on a comparison between the top third and bottom third scores on the Buss-Durkee Hostility Index.

RESULTS

Using a pixel-wise comparison, no brain region showed significant alterations in SERT binding among the 3 groups of subjects (aggressive alcoholic subjects, nonaggressive alcoholic subjects, and healthy controls) or between the combined alcoholic group and healthy controls. None of the clinical measures (including measures of aggression) correlated with SERT binding in the alcoholic subjects.

CONCLUSION

Contrary to prior imaging reports using the nonselective ligand [(123)I]beta-CIT, we found no significant alterations of SERT density in alcoholic patients.

Amygdala serotonin transporters in alcoholics measured by whole hemisphere autoradiography

BACKGROUND

A dysfunction in brain serotonin turnover is a well-established factor associated with the impulsive and sociopathic behavior in alcoholics. The conjuncted alterations in functioning of serotonin transporter (SERT) may play a role in the regulation of emotional balance, judgement, and the adverse behavioral effects of ethanol misuse. These traits may be related to serotonergic regulation in the amygdala and prefrontal cortex.

METHODS

The binding of [(3)H]citalopram to SERT was evaluated in the amygdala of Cloninger type 1 and 2 alcoholics (n = 17), and nonalcoholic control subjects (n = 10) by postmortem whole-hemisphere autoradiography.

RESULTS

The SERT binding was substantially lower in the dorsal amygdala in alcoholic subjects when compared with the controls (-28%, effect size 1.26, P = 0.016). In secondary analysis, this reduction was observed in both alcoholic subgroups (-26% in type 1 alcoholics, and -33% in type 2 alcoholics). In ventral amygdala, no alteration was observed. There were significant correlations between the SERT binding in dorsal amygdala and in previous results from frontal cortical areas in alcoholics, depending on the type of alcoholic.

CONCLUSIONS

These results suggest that SERT binding in the amygdala, as well as the differential regulation of the SERT in amygdala and frontal cortex in alcoholics may help to explain the dysfunctional regulation of emotions in alcoholics.

Puberty, hormones, and sex differences in alcohol abuse and dependence

Sex differences in patterns of drinking and rates of alcohol abuse and dependence begin to emerge during the transition from late puberty to young adulthood. Increases in pubertal hormones, including gonadal and stress hormones, are a prominent developmental feature of adolescence and could contribute to the progression of sex differences in alcohol drinking patterns during puberty. This paper reviews experimental and correlational studies of gonadal and stress-related hormone changes and their effects on alcohol drinking and other associated actions of alcohol. Mechanisms are suggested by which reproductive hormones and stress-related hormones may modulate neural circuits within the brain reward system to produce sex differences in alcohol drinking patterns and vulnerability to alcohol abuse and dependence which become apparent during the late pubertal period.

Neuroimaging studies of serotonin gene polymorphisms: exploring the interplay of genes, brain, and behavior

Because of the unique ability it provides to investigate information processing at the level of neural systems, functional neuroimaging is a powerful tool to explore the relationship between genes, brain, and behavior. Recently, functional neuroimaging has provided dramatic illustrations of how a promoter polymorphism in the human serotonin transporter gene, which has been weakly related to several dimensions of emotional behaviors (such as neuroticism and anxiety traits), is strongly related to the engagement of neural systems--namely, the amygdala and subgenual prefrontal cortex, subserving emotional information processing. This review will outline the experimental strategy by which these genetic effects on brain function have been explored and highlight the effectiveness of this strategy to delineate biological pathways and mechanisms contributing to the emergence of individual differences in brain function that potentially bias behavior and risk for psychiatric illness.

Serotonergic dysfunction: brain imaging and behavioral correlates

Identification of gene-environment and gene-gene interactions has become increasingly important in understanding psychiatric disorders. Dysfunction of central serotonergic neurotransmission has been implicated in alcoholism, depression, and anxiety. We review the literature on nonhuman primates that assesses the interaction between the genetic constitution of the regulatory region ofthe serotonin transporter (5-HTT) and environmental factors. Prospective studies in nonhuman primates that underwent social stress found a reduction of theserotonin turnover rate among carriers of one or two short alleles in a functional polymorphism of the 5-HTT promoter. In these primates, brain imaging studies showed a relative increase in the availability of raphe serotonin transporters. A low serotonin turnover rate and a high availability of serotonin transporters were associated with reduced response to excessive alcohol intake, anxiety, and impulsive aggression. Animal experiments point to a relationship between serotonergic dysfunction, negative mood states, and excessive alcohol intake, which may in part be mediated by reduced alcohol-induced sedation.

Low level of response to alcohol as associated with serotonin transporter genotype and high alcohol intake in adolescents

BACKGROUND

A low level of response to alcohol has been associated with both the genetic constitution of the regulatory region (SLC6A4) of the human serotonin (5-hydroxytryptamine, 5-HT) transporter (5-HTT) and with future alcohol intake and an increased risk for alcoholism. To date, all studies of relevant polymorphisms have been carried out in populations in the United States.

METHODS

Data were extracted from a subset (n = 243) of a cohort of children who have been observed since birth through evaluation of the family history of alcoholism and psychosocial risk influences. At age 16 years, the response to alcohol was assessed with the Self-Rating of the Effects of Alcohol (SRE) questionnaire, and the average amount of alcohol intake per month was assessed during the prior 6 months. Additional variables that were measured included the 5-HTT genotype, externalizing behavior, and sociodemographic variables, such as gender and age.

RESULTS

The level of response to alcohol was significantly lower among carriers of two long alleles of the 5-HTT regulatory region compared with carriers of one or two short alleles (Mann-Whitney U = 5225.0, p = .005). In a multiple regression analysis, the level of response to alcohol and externalizing behavior but not psychosocial factors significantly predicted the average amount of alcohol intake per month.

CONCLUSIONS

This study demonstrates that, independent of the assessed psychosocial variables, the 5-HTT genotype correlated with the level of response to alcohol and predicted alcohol intake among 16-year-old adolescents.

Imaging genetics: perspectives from studies of genetically driven variation in serotonin function and corticolimbic affective processing

Advances in molecular biology and neuroimaging have provided a unique opportunity to explore the relationships between genes, brain, and behavior. In this review, we will briefly outline the rationale for studying genetic effects on brain function with neuroimaging. We will then use studies of genetically driven variation in serotonin transporter function on corticolimbic structure and function to highlight the effectiveness of this strategy to delineate biological pathways and mechanisms by which individual differences in brain function emerge and potentially bias behavior and risk for psychiatric illness. In a series of studies, a relatively frequent regulatory variant of the human serotonin transporter gene (5-HTTLPR) has been demonstrated to bias the reactivity of the amygdala to salient environmental cues. Moreover, the 5-HTTLPR affects the development of a broader corticolimbic circuit and alters the functional integration of emotional information between the amygdala and medial prefrontal cortex. In turn, corticolimbic circuit function predicts individual differences in an experimental index of temperamental anxiety and, thus, might reflect a predictive biological marker of increased risk for mood disorders associated with the 5-HTTLPR.

Glucose utilization in the medial prefrontal cortex correlates with serotonin turnover rate and clinical depression in alcoholics

We measured the serotonin metabolite 5-hydroxyindoleacetic acid (5-HIAA) in cerebrospinal fluid (CSF), regional cerebral glucose uptake (rCMRglc) as assessed with positron emission tomography in the medial prefrontal cortex (PFC) and severity of clinical depression (Beck's Depression Inventory, BDI) in detoxified male alcoholics and age-matched healthy men. In alcoholics, the severity of clinical depression was negatively correlated with rCMRglc in the medial PFC and positively with CSF 5-HIAA concentrations. A voxel-based analysis showed that the strongest correlation between CSF 5-HIAA levels and rCMRglc was found in alcoholics in the left orbitofrontal and medial PFC (BA10 and BA11); no significant correlations were observed among healthy control subjects. This pilot study indicates that a dysfunction of medial PFC may interact with central serotonin turnover and negative mood states during early abstinence.

Pharmacogenomics of alcohol response and addiction

Alcoholism is a complex psychiatric disorder that has high heritability (50-60%) and is relatively common; in the US the lifetime prevalence of alcohol dependence is 20% in men and 8% in women. Current psychosocial and pharmacological therapies have relatively modest effects. Treatment is complicated by the fact that alcoholism is often co-morbid with other disorders, including anxiety, depression, and antisocial personality disorder. Approximately 80% of alcoholics smoke cigarettes and there is considerable genetic overlap between nicotine and alcohol addiction. Convergent evidence supports the classification of alcoholics into two broad categories: type 1 - later onset with feelings of anxiety, guilt, and high harm avoidance; and type 2 - early age of onset, usually men, impulsive, antisocial, and with low levels of brain serotonin. The pharmacogenomics of alcohol response is well established; genetic variants for the principal enzymes of alcohol metabolism influence drinking behavior and protect against alcoholism. Vulnerability to alcoholism is likely to be due to multiple interacting genetic loci of small to modest effects. First-line therapeutic targets for alcoholism are neurotransmitter pathway genes implicated in alcohol use. Of particular interest are the 'reward pathway' (serotonin, dopamine, GABA, glutamate, and beta endorphin) and the behavioral stress response system (corticotrophin-releasing factor and neuropeptide Y). Common functional polymorphisms in these genes are likely to be predictive (although each with small effect) of individualized pharmacological responses. Genetic studies, including case-control association studies and genome wide linkage studies, have identified associations between alcoholism and common functional polymorphisms in several candidate genes. Meanwhile, the current pharmacological therapies for alcoholism are effective in some alcoholics but not all. Some progress has been made in elucidating the pharmacogenomic responses to these drugs, particularly in the context of the type 1/type 2 classification system for alcoholics.

Functional neuroimaging of genetic variation in serotonergic neurotransmission

Serotonin (5-hydroxytryptamine; 5-HT) is a potent modulator of the physiology and behavior involved in generating appropriate responses to environmental cues such as danger or threat. Furthermore, genetic variation in 5-HT subsystem genes can impact upon several dimensions of emotional behavior including neuroticism and psychopathology, but especially anxiety traits. Recently, functional neuroimaging has provided a dramatic illustration of how a promoter polymorphism in the human 5-HT transporter (5-HTT) gene, which has been weakly related to these behaviors, is strongly related to the engagement of neural systems, namely the amygdala, subserving emotional processes. In this commentary, we discuss how functional neuroimaging can be used to characterize the effects of polymorphisms in 5-HT subsystem genes on the response of neural circuits underlying the generation and regulation of mood and temperament as well as susceptibility to affective illness. We argue that in time, such knowledge will allow us to not only transcend phenomenological diagnosis and represent mechanisms of disease, but also identify at-risk individuals and biological pathways for the development of new treatments.

Outcome predictors in substance use disorders

Given the heterogeneous nature of substance abuse, it is notable that several predictors of response are independent of the primary drug of abuse or the treatment setting [208]. Although the strength of the relationship of predictor to outcome varies, the following factors have been identified consistently: severity of dependence or withdrawal; psychiatric comorbidity; substance-related problems; motivation (abstinence commitment); length of treatment; negative affective states; cognitive factors; personality traits and disorders; coping skills; multiple substance abuse; contingency contracting or coercion; genetic factors; sleep architecture; urges and craving; self-efficacy; and economic and social factors. Although it is well known that severity of dependence (including polysubstance abuse), serious psychiatric comorbidity, and social problems are associated with poor treatment response, only recently has research examined the efficacy of intervention strategies that specifically address these problems. Adequate treatment of psychiatric comorbidity and improvement in social, economic, and family functioning lead to better treatment outcomes. The development of specific techniques to enhance self-efficacy, motivation, coping skills, and functioning in the community are concrete examples of how the identification of factors associated with positive outcomes has led to the development of new treatments. Despite significant accomplishments, the field is left with many unanswered questions. Although several biologic markers, such as neuroendocrine response and sleep architecture, show promise as outcome predictors, it is not known whether these are critical factors in the initiation of substance use or its progression to dependence. Determining whether biologic markers are epiphenomena reflecting the amount and duration of substance abuse or are fundamental to the pathophysiology of dependence is a matter of urgent concern. With some exceptions, identification of biologic predictors has not led to innovative therapies. One of these exceptions is the development of naltrexone for the treatment of alcoholism, which was based in a solid theoretical rationale and followed by hypothesis-driven experiments. Similar opportunities should emerge from current basic science and clinical research. The application of pharmacogenetic techniques to the field of addiction also holds great promise. As future studies are undertaken, researchers and clinicians must be mindful that differences in outcome predictors across drugs of abuse and treatments may emerge as subgroups of individuals with addictive disorders and new therapies are identified. There is already evidence that early onset alcoholism is associated with poor response under some circumstances, yet may be a predictor of response to targeted pharmacotherapy with ondansetron [64, 112]. As the ability to subtype disorders based on meaningful biologic differences grows, it is anticipated that several relevant outcome predictors that are specific for pharmacotherapy will emerge.