Serotonin: imaging findings in eating disorders

Microbiota in anorexia nervosa: potential for treatment

Anorexia nervosa (AN) is characterised by the restriction of energy intake in relation to energy needs and a significantly lowered body weight than normally expected, coupled with an intense fear of gaining weight. Treatment of AN is currently based on psychological and refeeding approaches, but their efficacy remains limited since 40% of patients after 10 years of medical care still present symptoms of AN. The intestine hosts a large community of microorganisms, called the "microbiota", which live in symbiosis with the human host. The gut microbiota of a healthy human is dominated by bacteria from two phyla: Firmicutes and, majorly, Bacteroidetes. However, the proportion in their representation differs on an individual basis and depends on many external factors including medical treatment, geographical location and hereditary, immunological and lifestyle factors. Drastic changes in dietary intake may profoundly impact the composition of the gut microbiota, and the resulting dysbiosis may play a part in the onset and/or maintenance of comorbidities associated with AN, such as gastrointestinal disorders, anxiety and depression, as well as appetite dysregulation. Furthermore, studies have reported the presence of atypical intestinal microbial composition in patients with AN compared with healthy normal-weight controls. This review addresses the current knowledge about the role of the gut microbiota in the pathogenesis and treatment of AN. The review also focuses on the bidirectional interaction between the gastrointestinal tract and the central nervous system (microbiota-gut-brain axis), considering the potential use of the gut microbiota manipulation in the prevention and treatment of AN.

The effects of acute tryptophan depletion on instrumental reward learning in anorexia nervosa - an fMRI study

BACKGROUND

The serotonin (5-HT) hypothesis of anorexia nervosa (AN) posits that individuals predisposed toward or recovered from AN (recAN) have a central nervous hyperserotonergic state and therefore restrict food intake as a means to reduce 5-HT availability (via diminished tryptophan-derived precursor supply) and alleviate associated negative mood states. Importantly, the 5-HT system has also been generally implicated in reward processing, which has also been shown to be altered in AN.

METHODS

In this double-blind crossover study, 22 individuals recAN and 25 healthy control participants (HC) underwent functional magnetic resonance imaging (fMRI) while performing an established instrumental reward learning paradigm during acute tryptophan depletion (ATD; a dietary intervention that lowers central nervous 5-HT availability) as well as a sham depletion.

RESULTS

On a behavioral level, the main effects of reward and ATD were evident, but no group differences were found. fMRI analyses revealed a group × ATD × reward level interaction in the ventral anterior insula during reward anticipation as well as in the medial orbitofrontal cortex during reward consumption.

DISCUSSION

The precise pattern of results is suggestive of a 'normalization' of reward-related neural responses during ATD in recAN compared to HC. Our results lend further evidence to the 5-HT hypothesis of AN. Decreasing central nervous 5-HT synthesis and availability during ATD and possibly also by dieting may be a means to normalize 5-HT availability and associated brain processes.

No effects of acute tryptophan depletion on anxiety or mood in weight-recovered female patients with anorexia nervosa

BACKGROUND

Previous studies have suggested that individuals recovered from anorexia nervosa (AN) are characterized by increased serotonergic (5-HT) activity that might be related to elevated levels of anxiety. Assuming these traits to be also present in individuals at risk for AN, it was further hypothesized that restricting food intake might be a means to temporarily alleviate dysphoric affective states by reducing central nervous availability of tryptophan (TRP), the sole precursor of 5-HT. One study that supported this hypothesis found anxiolytic effects in individuals with a history of AN during an experimentally induced short-term depletion of TRP supply to the brain.

METHODS

In this placebo-controlled, double-blind cross-over study, 22 patients weight-recovered from AN (recAN) and 25 healthy control participants (HC) completed questionnaires assessing anxiety and momentary mood during acute tryptophan depletion (ATD), a dietary intervention that lowers central 5-HT synthesis.

RESULTS

The ATD procedure effectively reduced the ratio of TRP to competing for large neutral amino acids in the peripheral blood, indicating decreased TRP supply to the brain. Effects of ATD on anxiety and mood did not differ between recAN and HC. Bayesian null hypothesis testing confirmed these initial results.

DISCUSSION

Our results do not support the hypothesis that short-term depletion of TRP and its impact on the brain 5-HT reduces anxiety or improves mood in AN. As the evidence for the role of 5-HT dysfunction on affective processes in patients with AN is limited, further studies are needed to assess its relevance in the pathophysiology of AN.

Sequelae of Eating Disorders at Imaging

Although eating disorders are common, they tend to be underdiagnosed and undertreated because social stigma tends to make patients less likely to seek medical attention and less compliant with medical treatment. Diagnosis is crucial because these disorders can affect any organ system and are associated with the highest mortality rate of any psychiatric disorder. Because of this, imaging findings, when recognized, can be vital to the diagnosis and management of eating disorders and their related complications. The authors familiarize the radiologist with the pathophysiology and sequelae of eating disorders and provide an overview of the related imaging findings. Some imaging findings associated with eating disorders are nonspecific, and others are subtle. The presence of these findings should alert the radiologist to correlate them with the patient's medical history and laboratory results and the clinical team's findings at the physical examination. The combination of these findings may suggest a diagnosis that might otherwise be missed. Topics addressed include (a) the pathophysiology of eating disorders, (b) the clinical presentation of patients with eating disorders and their medical complications and sequelae, (c) the imaging features associated with common and uncommon sequelae of eating disorders, (d) an overview of management and treatment of eating disorders, and (e) conditions that can mimic eating disorders (eg, substance abuse, medically induced eating disorders, and malnourishment in patients with cancer). Online supplemental material is available for this article. ^©RSNA, 2022.

Immunoinflammatory processes: Overlapping mechanisms between obesity and eating disorders?

Obesity and eating disorders are conditions that involve eating behaviors and are sometimes comorbid. Current evidence supports alterations in immunoinflammatory processes in both obesity and eating disorders. A plausible hypothesis is that immunoinflammatory processes may be involved in the pathophysiology of obesity and eating disorders. The aim of this review is to highlight the link between obesity and eating disorders, with a particular focus on immunoinflammatory processes. First, the relation between obesity and eating disorders will be presented, followed by a brief review of the literature on their association with immunoinflammatory processes. Second, developmental factors will be discussed to clarify the link between obesity, eating disorders, and immunoinflammatory processes. Genetic and epigenetic risk factors as well as the potential roles of stress pathways and early life development will be presented. Finally, implications of these findings for future research are discussed. This review highlighted biological and developmental aspects that overlap between obesity and EDs, emphasizing the need for biopsychosocial research approaches to advance current knowledge and practice in these fields.

Selective Serotonin Reuptake Inhibitors and Hydroxyzine in the Treatment of Avoidant/Restrictive Food Intake Disorder in Children and Adolescents: Rationale and Evidence

Objective: Despite lack of evidence, various pharmacological agents are judiciously used to manage anxiety in avoidant restrictive food intake disorder (ARFID). We aimed to explore the effectiveness of selective serotonin reuptake inhibitors (SSRIs), either alone or in combination with hydroxyzine, in a well-defined cohort of children and adolescents with ARFID receiving treatment in a partial hospitalization program for eating disorders. Methods: We conducted a retrospective chart review of 53 patients with ARFID who were prescribed an SSRI (n = 39) or SSRI with hydroxyzine (n = 14). We investigated changes from admission to discharge in these two medication groups on various outcome measures assessing weight, eating behaviors, mood, anxiety, and fears about food. Results: Participants in the SSRI+hydroxyzine group were significantly older than those in the SSRI only group. The majority of participants in both groups exhibited the fear presentation of ARFID. Repeated-measures analysis of variance yielded a significant main effect for treatment for all outcome measures, indicating that patients in both groups experienced improvements in weight, eating behaviors, mood, anxiety, and fears of food. A significant main effect for medication group emerged on the Children's Depression Inventory, suggesting that the group receiving SSRI+hydroxyzine experienced greater depressive symptomatology than the SSRI-only group. We did not find any significant interactions, indicating that participants in both medication groups experienced similar improvements over the course of treatment. Conclusion: These results provide preliminary evidence that SSRIs and hydroxyzine may be helpful in the treatment of children and adolescents with ARFID. Given that hydroxyzine was prescribed to patients who experienced high pre- and/or postmeal anxiety, it possibly contributed to similar decreases in anxiety and fear of food in a more challenging subset of patients. Randomized, placebo-controlled studies for children and adolescents with ARFID are warranted to better evaluate and understand the efficacy of SSRIs and hydroxyzine in this clinical population.

An In Vitro Approach to Studying the Microbial Community and Impact of Pre and Probiotics under Anorexia Nervosa Related Dietary Restrictions

Individuals with anorexia nervosa (AN) often suffer psychological and gastrointestinal problems consistent with a dysregulated gut microbial community. Psychobiotics have been postulated to modify microbiota and improve mental well-being and gut symptoms, but there is currently a lack of evidence for such approaches in AN. The aim of this study was to use an in vitro colonic model to evaluate the impact of dietary restrictions associated with AN on the intestinal ecosystem and to assess the impact of pre and probiotic intervention. Bacteriology was quantified using flow cytometry combined with fluorescence in situ hybridisation and metabolic end products (including neurotransmitters) by gas chromatography and liquid chromatography mass spectrometry Consistent with previous research, the nutritional changes significantly reduced total microbiota and metabolites compared with healthy conditions. Pre and probiotic supplementation on restricted conditions enhanced the microbial community and modulated metabolic activity to resemble that of a healthy diet. The model system indicates that nutritional changes associated with AN can impact the microbial community, and that these changes can, at least in part, be restored through the use of pre and probiotic interventions.

Ketamine as a Treatment for Anorexia Nervosa: A Narrative Review

Anorexia nervosa (AN) is a highly complex disorder to treat, especially in severe and enduring cases. Whilst the precise aetiology of the disorder is uncertain, malnutrition and weight loss can contribute to reductions in grey and white matter of the brain, impairments in neuroplasticity and neurogenesis and difficulties with cognitive flexibility, memory and learning. Depression is highly comorbid in AN and may be a barrier to recovery. However, traditional antidepressants are often ineffective in alleviating depressive symptoms in underweight patients with AN. There is an urgent need for new treatment approaches for AN. This review gives a conceptual overview for the treatment of AN with ketamine. Ketamine has rapid antidepressant effects, which are hypothesised to occur via increases in glutamate, with sequelae including increased neuroplasticity, neurogenesis and synaptogenesis. This article provides an overview of the use of ketamine for common psychiatric comorbidities of AN and discusses particular safety concerns and side effects. Potential avenues for future research and specific methodological considerations are explored. Overall, there appears to be ample theoretical background, via several potential mechanisms, that warrant the exploration of ketamine as a treatment for adults with AN.

The peril and promise of sensitivity in eating disorders

Differential susceptibility, a reconceptualization of the diathesis-stress model of psychopathology, describes gene-environment interactions that reflect individual differences in responsiveness to environmental influences, both detrimental and beneficial. This model has been described metaphorically by the classification of orchids, which thrive under optimal care but wither under adverse conditions, and dandelions, which weather broad environmental circumstances but are less responsive to careful cultivation. Etiological research in the field of eating disorders has largely focused on the identification of specific behavioral phenotypes, temperamental traits, genotypes and neurobiological processes that confer risk. In this article, we propose that these putative vulnerability factors represent phenotypes and endophenotypes of a genetic predisposition towards environmental sensitivity. We assert that this sensitivity not only transmits eating disorder risk but also confers resilience, depending on the circumstances. In particular, we propose that differential susceptibility can be used as a framework to organize disparate temperamental and neurobiological findings and their complex interplay with various developmental, environmental and sociocultural influences to increase eating disorder risk and treatment responsiveness. Finally, we assert that viewed through the lens of differential susceptibility, sensitivity can be leveraged to refine our interventions and develop novel treatment and prevention strategies to support favorable outcomes for individuals with eating disorders.

Maternal separation alters the reward system of activity-based anorexia rats

Maternal separation (MS) is a known chronic stressor in the postnatal period and when associated with another paradigm like the activity-based anorexia (ABA) rat model, causes different effects in the two sexes. In ABA females, the separation leads to increased hyperactivity and anxiety reduction, whereas, in males, the separation induces decreased locomotor activity without similar reduction of anxiety-like behaviors as observed in females. To understand the mechanisms altered by MS in synergy with the induction of the anorexic-like phenotype, we considered the reward system, which involves neurons synthesizing dopamine (DA) in the ventral tegmental area (VTA), substantia nigra pars compacta, and serotoninergic neurons in the dorsal raphe nucleus. Moreover, we analyzed the orexin circuit in the lateral hypothalamic area (LHA), which affects DA synthesis in the VTA and is also known to regulate food consumption and locomotor activity. Rats of both sexes were exposed to the two paradigms (MS and ABA), leading to four experimental groups for each sex: non-separated control (CON), non-separated ABA groups (ABA), MS control (MSCON), and MS plus ABA groups (MSABA). Immunohistochemistry analysis was performed to determine quantitative differences in the number of cells expressing DA, orexin, and serotonin (5-HT) among the experimental groups. The results showed that, in the DA system, the effect of MS was more evident in females than in males, with a substantial increase in DA cells in the VTA of MSABA. However, the analysis of the orexin system revealed a similar cellular increment in the LHA in the non-separated ABA groups of both sexes. Regarding 5-HT, there was an opposite effect in males and females of the MSABA groups, with only females showing a greater density of 5-HT cells. The changes in the reward system could partially explain the behavioral data: the hyperactivity, weight loss, and decreased anxiety levels of the MSABA females could be linked to an increase in DA and 5-HT cells, whereas in males, MS could mitigate the behavioral effects of the ABA protocol affecting the anxiety levels and locomotor activity through a lack of increased activation of the reward system.

Acute Stress Exposure Alters Food-Related Brain Monoaminergic Profiles in a Rat Model of Anorexia

BACKGROUND

Adverse life experiences are a major risk factor for anorexia nervosa (AN). Eating-provoked anxiousness associated with AN is postulated to be due to food-related exaggerated serotonin activity in the brain and imbalances of monoamine neurotransmitters.

OBJECTIVES

Using a rodent model of stress-induced hypophagia, we investigated if stress exposure augments food-related serotonin turnover and imbalances in measures of brain serotonin and dopamine activity in manners consistent with anxiousness toward food and restricted eating.

METHODS

Adult male F344 rats were conditioned to associate an audio cue with daily food over 2 weeks, after which half of the rats were exposed to a single episode of tail shocks (stress) or left undisturbed (nonstressed). All rats were killed 48 h later, during a control period, the food-associated cue, or a period of food access. Serotonin, dopamine, and norepinephrine, as well as metabolite concentrations, were assessed across brain regions comprising reward, emotion, and feeding circuits relevant to AN in acutely stressed and nonstressed rats using HPLC. Statistical significance level was 5%.

RESULTS

Stress-induced rat hypophagia paralleled an augmented serotonin turnover in response to the food-associated cue in the hypothalamus and hippocampus, as well as food access in the hypothalamus and cortical areas (all P < 0.05). Stress exposure increased the ratio of serotonin to dopamine metabolites across several brain areas, but the magnitude of this imbalance was further augmented during the food-associated cue and food access in the brainstem, hippocampus, and cortical areas (all P < 0.05). Finally, stress lowered norepinephrine concentrations by 18% in the hypothalamus (P < 0.05).

CONCLUSIONS

The observed stress-induced changes to monoamine profiles in rats could have key implications for physiological states that contribute to restricted eating and may hold relevance for the development of AN precipitated by adverse life experiences.

The Mediating Effect of Self-Control on Depression and Tendencies of Eating Disorders in Adolescents

Self-control is very important for the adaptation among adolescents. It is associated with depression and tendencies of eating disorders. This study aimed to investigate the relationship between the two and the mediating role of self-control for adolescents. In total, 1,231 adolescents (11-18 years) participated in this study. Self-control, depression, and tendencies of eating disorders were evaluated using the Dual-Mode of Self-Control Scale (DMSC-S), 11-item Kutcher Adolescent Depression Scale (KADS-11), and Eating Attitudes Test (EAT-26). The correlations among these factors were analyzed using mediating effect models. Girls had higher scores on the both subscales (impulse system and control system) of DMSC-S (P < 0.001). Those between 15-18 years had higher scores on impulse system than those between 11-14 years (P < 0.001). A significant mediating effect (12.8%) of the impulse system was observed between depression and tendencies of eating disorders in adolescents.

International Union of Basic and Clinical Pharmacology. CX. Classification of Receptors for 5-hydroxytryptamine; Pharmacology and Function

5-HT receptors expressed throughout the human body are targets for established therapeutics and various drugs in development. Their diversity of structure and function reflects the important role 5-HT receptors play in physiologic and pathophysiological processes. The present review offers a framework for the official receptor nomenclature and a detailed understanding of each of the 14 5-HT receptor subtypes, their roles in the systems of the body, and, where appropriate, the (potential) utility of therapeutics targeting these receptors. SIGNIFICANCE STATEMENT: This review provides a comprehensive account of the classification and function of 5-hydroxytryptamine receptors, including how they are targeted for therapeutic benefit.

Moving towards specificity: A systematic review of cue features associated with reward and punishment in anorexia nervosa

Models of anorexia nervosa (AN) posit that symptoms are maintained through deficient reward and enhanced punishment processing. However, theoretical and empirical inconsistencies highlight the need for a more nuanced conceptualization of this literature. Our goal was to comprehensively review the research on reward and punishment responding in AN from a cue-specific lens to determine which stimuli evoke or discourage reward and punishment responses in this population, and, ultimately, what properties these rewarding and punishing cues might share. A systematic review interrogating reward and punishment responses to specific cues yielded articles (n = 92) that examined responses to disorder relevant (e.g., food) and irrelevant (e.g., money) stimuli across self-report, behavioral, and biological indices. Overall, in most studies individuals with AN exhibited aversive responses to cues signaling higher body weights, social contexts, and monetary losses, and appetitive responses to cues for weight loss behaviors and thinness. Findings were more mixed on responses to palatable food and monetary gains. Results highlight that reward and punishment responding in AN are context specific and may be affected by varied stimulus qualities (e.g., predictability, controllability, delay, effort). Increasing specificity in future research on reward and punishment mechanisms in AN will better inform development of precisely-targeted interventions.

The Explanation of Eating Disorders: A Critical Analysis

Eating disorders (EDs) are one of the most severe and complex mental health problems facing researchers and clinicians today. The effective prevention and treatment of these conditions is therefore of paramount importance. However, at present our treatments fall short: generally demonstrating only poor to moderate efficacy, and often completely ineffective for severe or chronic cases. A possible reason for this is that the current theories underlying these treatments are flawed. In this paper, we review and evaluate several prominent theoretical explanations associated with current frontline and promising treatments for ED. In doing so, we identify fundamental problems within the construction of current ED explanations and their implications for treatment. In response to these findings, we propose several strategies for the construction of future ED explanations which we believe have the power to ameliorate these problems and potentially help to develop more efficacious treatment downstream.

Rethinking Therapeutic Strategies for Anorexia Nervosa: Insights From Psychedelic Medicine and Animal Models

Anorexia nervosa (AN) has the highest mortality rate of any psychiatric disease, yet available pharmacological treatments are largely ineffective due, in part, to an inadequate understanding of the neurobiological drivers that underpin the condition. The recent resurgence of research into the clinical applications of psychedelic medicine for a range of mental disorders has highlighted the potential for classical psychedelics, including psilocybin, to alleviate symptoms of AN that relate to serotonergic signaling and cognitive inflexibility. Clinical trials using psychedelics in treatment-resistant depression have shown promising outcomes, although these studies are unable to circumvent some methodological biases. The first clinical trial to use psilocybin in patients with AN commenced in 2019, necessitating a better understanding of the neurobiological mechanisms through which psychedelics act. Animal models are beneficial in this respect, allowing for detailed scrutiny of brain function and behavior and the potential to study pharmacology without the confounds of expectancy and bias that are impossible to control for in patient populations. We argue that studies investigating the neurobiological effects of psychedelics in animal models, including the activity-based anorexia (ABA) rodent model, are particularly important to inform clinical applications, including the subpopulations of patients that may benefit most from psychedelic medicine.

The Gut Microbiome in Anorexia Nervosa: Friend or Foe?

The human gut microbiome is emerging as a key modulator of homeostasis, with far-reaching implications for various multifactorial diseases, including anorexia nervosa (AN). Despite significant morbidity and mortality, the underlying mechanisms of this eating disorder are poorly understood, but the classical view defining AN as a purely psychiatric condition is increasingly being challenged. Accumulating evidence from comparative studies of AN and healthy fecal microbial composition reveals considerable low divergence and altered taxonomic abundance of the AN gut microbiome. When integrated with preclinical data, these findings point to a significant role of the gut microbiome in AN pathophysiology, via effects on host energy metabolism, intestinal permeability, immune function, appetite, and behavior. While complex causal relationships between genetic risk factors, dietary patterns and microbiome, and their relevance for AN onset and perpetuation have not been fully elucidated, preliminary clinical studies support the use of microbiome-based interventions such as fecal microbiota transplants and probiotics as adjuvants to standard AN therapies. Future research should aim to move from observational to mechanistic, as dissecting how specific microbial taxa interact with the host to impact the development of AN could help design novel therapeutic approaches that more effectively address the severe comorbidities and high relapse rate of this serious disorder.

Theory construction in the psychopathology domain: A multiphase approach

Our understanding of mental disorders is facilitated by our theoretical explanations of them. At present, these explanations are practically and theoretically insufficient; possessing widespread conceptual issues (e.g., lack of richness and specificity) and producing therapeutic treatments that lack effectiveness. In our view, one reason for such issues is that we are currently without a systematic method for the construction of these explanations. We therefore present to the reader the Phenomena Detection Method for Theory Construction (PDM-TC), a preliminary systematic framework for the construction of psychopathological explanation comprising three phases: (a) selecting an appropriate explanatory target, (b) developing a rich compositional description, and (c) developing a quality etiological explanation. Using theories of eating disorders as a sustained example, we demonstrate how current explanations of psychopathology execute the tasks associated with each of these phases insufficiently and how the conceptual issues they evidence can be ameliorated by the PDM-TC framework.

Eating Disorders: An Evolutionary Psychoneuroimmunological Approach

Eating disorders are evolutionarily novel conditions. They lead to some of the highest mortality rates of all psychiatric disorders. Several evolutionary hypotheses have been proposed for eating disorders, but only the intrasexual competition hypothesis is extensively supported by evidence. We present the mismatch hypothesis as a necessary extension to the current theoretical framework of eating disorders. This hypothesis explains the evolutionarily novel adaptive metaproblem that has arisen when mating motives conflict with the large-scale and easy availability of hyper-rewarding but obesogenic foods. This situation is exacerbated particularly in those contemporary environments that are characterized by sedentary lifestyles, ever-present junk foods, caloric surplus and the ubiquity of social comparisons that take place via social media. Our psychoneuroimmunological model connects ultimate-level causation with proximate mechanisms by showing how the adaptive metaproblem between mating motives and food rewards leads to chronic stress and, further, to disordered eating. Chronic stress causes neuroinflammation, which increases susceptibility to OCD-like behaviors that typically co-occur with eating disorders. Chronic stress upregulates the serotonergic system and causes dysphoric mood in anorexia nervosa patients. Dieting, however, reduces serotonin levels and dysphoric mood, leading to a vicious serotonergic-homeostatic stress/starvation cycle whereby cortisol and neuroinflammation increase through stringent dieting. Our psychoneuroimmunological model indicates that between-individual and within-individual variation in eating disorders partially arises from (co)variation in gut microbiota and stress responsivity, which influence neuroinflammation and the serotonergic system. We review the advances that have been made in recent years in understanding how to best treat eating disorders, outlining directions for future clinical research. Current evidence indicates that eating disorder treatments should aim to reduce the chronic stress, neuroinflammation, stress responsivity and gut dysbiosis that fuel the disorders. Connecting ultimate causes with proximate mechanisms and treating biopsychosocial causes rather than manifest symptoms is expected to bring more effective and sophisticated long-term interventions for the millions of people who suffer from eating disorders.

Can Gut Microbiota and Lifestyle Help Us in the Handling of Anorexia Nervosa Patients?

Gut microbiota is composed of different microorganisms that play an important role in the host. New research shows that bidirectional communications happen between intestinal microbiota and the brain, which is known as the gut⁻brain axis. This communication is significant and could have a negative or positive effect depending on the state of the gut microbiota. Anorexia nervosa (AN) is a mental illness associated with metabolic, immunologic, biochemical, sensory abnormalities, and extremely low body weight. Different studies have shown a dysbiosis in patients with AN. Due to the gut⁻brain axis, it was observed that some of the symptoms could be improved in these patients by boosting their gut microbiota. This paper highlights some evidence connecting the role of microbiota in the AN onset and disease progress. Finally, a proposal is done to include the microbiota analysis as part of the recovery protocol used to treat AN patients. When conducting clinical studies of gut microbiota in AN patients, dysbiosis is expected to be found. Then the prescription of a personalized treatment rich in prebiotics and probiotics could be proposed to reverse the dysbiosis.

Adherence to the Mediterranean dietary pattern and incidence of anorexia and bulimia nervosa in women: The SUN cohort

OBJECTIVE

To our knowledge, no study has yet assessed the association between dietary patterns and incidence of eating disorders. This study aimed to assess the association between adherence to the Mediterranean dietary pattern (MDP) and incident risk of anorexia (AN) and bulimia nervosa (BN).

METHODS

We conducted a prospective cohort study of 11 800 women from the Seguimiento Universidad de Navarra follow-up project. Participants were classified as having incident AN or BN if they were free of AN or BN at baseline and reported a physician-made diagnosis of AN or BN during the follow-up period. Nutritional status, lifestyle, and behavioral variables were investigated and used as covariates. A validated 136-item food frequency questionnaire and the Trichopoulou score were used to assess adherence to the MDP.

RESULTS

After a median follow-up time of 9.4 y, 100 new cases of AN and BN were identified. The multivariate hazard ratio of AN and BN for the two upper categories of adherence to the MDP were 0.39 (95% CI: 0.20-0.75) and 0.32 (95% CI: 0.14-0.70; P_trend = 0.021). Inverse dose-response relationships were found for the consumption of cereals and olive oil and marginally for polyunsaturated fatty acid intake. To address reverse causation, multivariable linear regressions were run using a cross-sectional approach between adherence to the MDP and risk of AN and BN at baseline. No difference in adherence was found between participants with and without eating disorders.

CONCLUSIONS

Our results suggest a potential inverse association between the MDP and the risk of AN and BN. Additional longitudinal studies and trials are needed.

Impaired reversal learning in an animal model of anorexia nervosa

BACKGROUND

Clinical investigations indicate that anorexia nervosa (AN) is associated with impaired cognitive flexibility. Activity-based anorexia (ABA), a rodent behavioral model of AN, is characterized by compulsive wheel running associated with voluntary food restriction and progressive weight loss. The goal of this study was to test whether ABA is associated with impaired cognitive flexibility.

METHODS

Female Sprague-Dawley rats were trained to perform the attentional set-shifting test (ASST) to assess cognitive flexibility, including capacity for set-shifting and reversal learning. Rats were assigned to ABA or weight-loss paired control (WPC) conditions. Following baseline testing, the ABA group had access to food for 1h/d and access to running wheels 23h/d until 20% weight loss was voluntarily achieved. For the WPC group, running wheels were locked and access to food was restricted to reduce body weight at the same rate as the ABA group. ASST performance was assessed after weight loss, and again following weight recovery.

RESULTS

Compared to baseline, the ABA group (but not the WPC group) showed a significant decrement in reversal learning at low weight, with return to baseline performance following weight restoration. The other components of ASST were not affected.

CONCLUSIONS

Impaired reversal learning, indicative of increased perseverative responding, in the ABA model reveals its potential to recapitulate selective components of cortical dysfunction in AN. This finding supports the utility of the ABA model for investigations of the neural mechanisms underlying such deficits. Reversal learning relies on neural circuits involving the orbitofrontal cortex and thus the results implicate orbitofrontal abnormalities in AN-like state.

Grey matter volume in adolescents with anorexia nervosa and associated eating disorder symptoms

Anorexia nervosa (AN) is a mental health disorder of complex aetiology. Previous neuroimaging studies have found consistent global reductions in global grey matter volume of underweight girls with AN; however, differences in regional grey matter volumes are less consistent. The aims of this study were to investigate grey matter regional volumes of adolescent girls with AN before and after weight recovery and the relationship of any changes with clinical characteristics. We collected high-resolution T1-weighted images from 26 underweight girls with AN before weight gain and 20 healthy control volunteers. Clinical features were assessed using the Eating Disorder Examination Questionnaire. AN subjects displayed reduced grey matter volumes in the insula, amygdala, prefrontal, hippocampal and cingulate cortices and the precuneus, relative to healthy controls. In a subset of 10 AN subjects who were followed after weight recovery, grey matter volumes increased to near-control levels in the orbito- and medial prefrontal, insular, left hippocampal and mid- and posterior cingulate cortices and precuneus. The recovery of the right anterior thalamus and the left orbitofrontal cortex was correlated with improvements in eating concerns and shape concerns, respectively. However, large parts of the anterior cingulate cortex, caudate nuclei and right hippocampus did not display any grey matter recovery following a short-term of treatment. These results show that in adolescents with AN, some brain regions display marked recovery in grey matter volume following weight recovery, whereas others do not, considering grey mater recovery possibly linked to symptom improvement.

Neural correlates of altered feedback learning in women recovered from anorexia nervosa

Anorexia nervosa (AN) is associated with exaggerated self-control and altered reward-based decision making, but the underlying neural mechanisms are poorly understood. Consistent with the notion of excessive cognitive control, we recently found increased dorsal anterior cingulate cortex (dACC) activation in acutely ill patients (acAN) on lose-shift trials in a probabilistic reversal learning (PRL) task. However, undernutrition may modulate brain function. In attempt to disentangle trait from state factors, the current fMRI study investigated cognitive control in recovered patients (recAN). Thirty-one recAN and 31 healthy controls (HC) completed a PRL task during fMRI. Based on previous findings, we focused on hemodynamic responses during lose-shift behaviour and conducted supplementary functional connectivity analysis. RecAN showed elevated lose-shift behaviour relative to HC. On the neural level, recAN showed normal dACC responses, but increased activation in fronto-parietal control regions. A trend for increased coupling between frontal and parietal regions of interest was also evident in recAN. The current findings in recAN differ from those in our previous study in acAN. While aberrant dACC response to negative feedback may be a correlate of the underweight state in acAN, impaired behavioural adaptation and elevated activation of cognitive control regions in recAN is suggestive of altered neural efficiency.

A systematic investigation of the differential roles for ventral tegmentum serotonin 1- and 2-type receptors on food intake in the rat

Central serotonin (5-HT) pathways are known to influence feeding and other ingestive behaviors. Although the ventral tegmentum is important for promoting the seeking and consumption of food and drugs of abuse, the roles of 5-HT receptor subtypes in this region on food intake have yet to be comprehensively examined. In these experiments, food restricted rats were given 2-h access to rat chow; separate groups of non-restricted animals had similar access to a sweetened fat diet. Feeding and locomotor activity were monitored following ventral tegmentum stimulation or blockade of 5-HT1A, 5-HT1B, 5-HT2A, 5-HT2B, or 5-HT2C receptors. 5-HT1A receptor stimulation transiently inhibited rearing behavior and chow intake in food-restricted rats, and had a biphasic effect on non-restricted rats offered the palatable diet. 5-HT1B receptor agonism transiently inhibited feeding in restricted animals, but did not affect intake of non-restricted rats. In contrast, 5-HT1B receptor antagonism decreased palatable feeding. Although stimulation of ventral tegmental 5-HT2B receptors with BW723C86 did not affect hunger-driven food intake, it significantly affected palatable feeding, with a trend for an increasing intake at 2.0µg/side but not at 5.0µg/side. Antagonism of the same receptor modestly but significantly inhibited feeding of the palatable diet at 5.0µg/side ketanserin. Neither stimulation nor blockade of 5-HT2A or 5-HT2C receptors caused prolonged effects on intake or locomotion. These data suggest that serotonin's effects on feeding within the ventral tegmentum depend upon the specific receptor targeted, as well as whether intake is motivated by food restriction or the palatable nature of the offered diet.

New Insights in Anorexia Nervosa

Anorexia nervosa (AN) is classically defined as a condition in which an abnormally low body weight is associated with an intense fear of gaining weight and distorted cognitions regarding weight, shape, and drive for thinness. This article reviews recent evidences from physiology, genetics, epigenetics, and brain imaging which allow to consider AN as an abnormality of reward pathways or an attempt to preserve mental homeostasis. Special emphasis is put on ghrelino-resistance and the importance of orexigenic peptides of the lateral hypothalamus, the gut microbiota and a dysimmune disorder of neuropeptide signaling. Physiological processes, secondary to underlying, and premorbid vulnerability factors-the "pondero-nutritional-feeding basements"- are also discussed.

Contemporary views on the genetics of anorexia nervosa

Anorexia nervosa (AN) is a serious mental illness characterized by severe dietary restriction that leads to high rates of morbidity, chronicity, and mortality. Unfortunately, effective treatment is lacking and few options are available. High rates of familial aggregation and significant heritability suggested that the complex etiology of AN is affected by both genetic and environmental factors. In this paper, we review studies that reported common and rare genetic variation that influence susceptibility of AN through candidate gene studies, genome-wide association studies, and sequencing-based studies. We also discuss gene expression, methylation, imaging genetics, and pharmacogenetics to demonstrate that these studies have collectively advanced our knowledge of how genetic variation contributes to AN susceptibility and clinical course. Lastly, we highlight the importance of gene by environment interactions (G×E) and share our enthusiasm for the use of nutritional genomic approaches to elucidate the interaction among nutrients, metabolic intermediates, and genetic variation in AN. A deeper understanding of how nutrition alters genome stability, how genetic variation influences uptake and metabolism of nutrients, and how response to food components affects disordered eating, will lead to personalized dietary interventions and effective nutraceutical and pharmacological treatments for AN.

Interacting Neural Processes of Feeding, Hyperactivity, Stress, Reward, and the Utility of the Activity-Based Anorexia Model of Anorexia Nervosa

Anorexia nervosa (AN) is a psychiatric illness with minimal effective treatments and a very high rate of mortality. Understanding the neurobiological underpinnings of the disease is imperative for improving outcomes and can be aided by the study of animal models. The activity-based anorexia rodent model (ABA) is the current best parallel for the study of AN. This review describes the basic neurobiology of feeding and hyperactivity seen in both ABA and AN, and compiles the research on the role that stress-response and reward pathways play in modulating the homeostatic drive to eat and to expend energy, which become dysfunctional in ABA and AN.

Developmental emergence of an obsessive-compulsive phenotype and binge behavior in rats

RATIONALE

Obsessive-compulsive disorder (OCD) gradually emerges and reaches clinical significance during early adulthood. Whether a predisposition for OCD manifests as binge eating disorder earlier during adolescence is proposed.

OBJECTIVES

To further characterize how OCD-like behaviors increase across maturation and to determine whether an OCD-like predisposition increases the likelihood of binge eating during adolescence.

METHODS

Male and female Sprague-Dawley rats were injected with the tricyclic antidepressant clomipramine (CMI, 15 mg/kg) or saline vehicle twice daily between postnatal days 9-15. Both groups were tested for perseverative (spontaneous alternation) and anxiety-like (elevated plus maze; marble burying) behaviors during juvenility (day 28), adolescence (day 60), and adulthood (day 90). Both motivations to eat sucrose pellets and binge eating on fat were investigated.

RESULTS

Sex- and age-dependent increases in anxiety-like and perseverative behavior were observed in CMI subjects. Differences in consummatory behaviors emerged during late adolescence, while no significant differences in alternation or anxiety-like behaviors were detected between CMI and vehicle animals until adulthood. Adolescent CMI females consumed more sucrose pellets in 30 min relative to vehicle females, whereas adolescent CMI males consumed approximately half as much as vehicle males. Sucrose consumption did not differ between groups in adulthood. Adolescent CMI rats demonstrated more fat bingeing than vehicles, independent of sex.

CONCLUSIONS

OCD-like behaviors are emerging during adolescence, but sucrose consumption and fat bingeing in CMI-treated animals significantly precedes the appearance of anxiety and perseveration. This OCD-like phenotype emerges fully during adulthood, suggesting that eating may likely serve as a coping strategy in these animals.

Cerebral perfusion differences in women currently with and recovered from anorexia nervosa

Anorexia nervosa is a serious psychiatric disorder characterized by restricted eating, a pursuit of thinness, and altered perceptions of body shape and size. Neuroimaging in anorexia nervosa has revealed morphological and functional alterations in the brain. A better understanding of physiological changes in anorexia nervosa could provide a brain-specific health marker relevant to treatment and outcomes. In this study, we applied several advanced magnetic resonance imaging (MRI) techniques to quantify regional and global cerebral blood flow (CBF) in 25 healthy women (HC), 23 patients currently with anorexia (AN-C) and 19 patients in long-term weight recovery following anorexia (AN-WR). Specifically, CBF was measured with pseudo-continuous arterial spin labeling (pCASL) MRI and then verified by a different technique, phase contrast (PC) MRI. Venous T2 values were determined by T2 relaxation under spin tagging (TRUST) MRI, and were used to corroborate the CBF results. These novel techniques were implemented on a standard 3T MRI scanner without any exogenous tracers, and the total scan duration was less than 10min. Voxel-wise comparison revealed that the AN-WR group showed lower CBF in bilateral temporal and frontal lobes than the AN-C group. Compared with the HC group, the AN-C group also showed higher CBF in the right temporal lobe. Whole-brain-averaged CBF was significantly decreased in the AN-WR group compared with the AN-C group, consistent with the PC-MRI results. Venous T2 values were lower in the AN-WR group than in the AN-C group, consistent with the CBF results. A review of prior work examining CBF in anorexia nervosa is included in the discussion. This study identifies several differences in the cerebral physiological alterations in anorexia nervosa, and finds specific differences relevant to the current state of the disorder.

The use of animal models to decipher physiological and neurobiological alterations of anorexia nervosa patients

Extensive studies were performed to decipher the mechanisms regulating feeding due to the worldwide obesity pandemy and its complications. The data obtained might be adapted to another disorder related to alteration of food intake, the restrictive anorexia nervosa. This multifactorial disease with a complex and unknown etiology is considered as an awful eating disorder since the chronic refusal to eat leads to severe, and sometimes, irreversible complications for the whole organism, until death. There is an urgent need to better understand the different aspects of the disease to develop novel approaches complementary to the usual psychological therapies. For this purpose, the use of pertinent animal models becomes a necessity. We present here the various rodent models described in the literature that might be used to dissect central and peripheral mechanisms involved in the adaptation to deficient energy supplies and/or the maintenance of physiological alterations on the long term. Data obtained from the spontaneous or engineered genetic models permit to better apprehend the implication of one signaling system (hormone, neuropeptide, neurotransmitter) in the development of several symptoms observed in anorexia nervosa. As example, mutations in the ghrelin, serotonin, dopamine pathways lead to alterations that mimic the phenotype, but compensatory mechanisms often occur rendering necessary the use of more selective gene strategies. Until now, environmental animal models based on one or several inducing factors like diet restriction, stress, or physical activity mimicked more extensively central and peripheral alterations decribed in anorexia nervosa. They bring significant data on feeding behavior, energy expenditure, and central circuit alterations. Animal models are described and criticized on the basis of the criteria of validity for anorexia nervosa.

A meta-analysis of temperament in eating disorders

Although suggested as an important contributor to the development and maintenance of eating disorders, temperament has not previously been studied adopting a meta-analytical approach. We therefore pooled data (N = 14 studies; N = 3315 cases, N = 3395 controls) on Cloninger's temperament traits (novelty seeking, harm avoidance, reward dependence and persistence) in anorexia nervosa (AN), bulimia nervosa (BN), binge eating disorder (BED) and eating disorders not otherwise specified. Persistence was significantly higher than in the controls in all eating disorders except for BED the highest levels being observed in AN. Correspondingly, the highest effect sizes for harm avoidance were seen in AN. Novelty seeking was significantly elevated relative to the controls only in BN. Harm avoidance was significantly lower, and reward dependence was significantly higher in individuals who had recovered from AN than in those who remained ill. Future studies with a longitudinal design are needed to explore the temporal relationships between eating disorders and temperament traits.

The relation of weight suppression and body mass index to symptomatology and treatment response in anorexia nervosa

Weight suppression, the difference between highest past weight and current weight, is a robust predictor of clinical characteristics of bulimia nervosa; however, the influence of weight suppression in anorexia nervosa (AN) has been little studied, and to our knowledge, no study to date has investigated the ways in which the relevance of weight suppression in AN may depend upon an individual's current body mass index (BMI). The present study investigated weight suppression, BMI, and their interaction as cross-sectional and prospective predictors of psychological symptoms and weight in AN. Women with AN completed depression (Beck Depression Inventory-II) and eating disorder symptomatology measures (Eating Disorder Examination Questionnaire and Eating Disorders Inventory-3) at residential treatment admission (N = 350) and discharge (N = 238). Weight suppression and BMI were weakly correlated (r = -.22). At admission, BMI was positively correlated with all symptom measures except Restraint and Depression scores. Weight suppression was also independently positively correlated with all measures except Weight Concern and Body Dissatisfaction subscale scores. In analyses examining discharge scores (including admission values as covariates), the admission weight suppression × BMI interaction consistently predicted posttreatment psychopathology. Controlling for weight gain in treatment and age, higher admission weight suppression predicted lower discharge scores (less symptom endorsement) among those with lower BMIs; among those with higher BMIs, higher weight suppression predicted higher discharge scores. These results are the first to our knowledge to demonstrate that absolute and relative weight status are joint indicators of AN severity and prognosis. These findings may have major implications for conceptualization and treatment of AN.

Change in Brainstem Gray Matter Concentration Following a Mindfulness-Based Intervention is Correlated with Improvement in Psychological Well-Being

Individuals can improve their levels of psychological well-being (PWB) through utilization of psychological interventions, including the practice of mindfulness meditation, which is defined as the non-judgmental awareness of experiences in the present moment. We recently reported that an 8-week-mindfulness-based stress reduction (MBSR) course lead to increases in gray matter concentration in several brain areas, as detected with voxel-based morphometry of magnetization prepared rapid acquisition gradient echo MRI scans, including the pons/raphe/locus coeruleus area of the brainstem. Given the role of the pons and raphe in mood and arousal, we hypothesized that changes in this region might underlie changes in well-being. A subset of 14 healthy individuals from a previously published data set completed anatomical MRI and filled out the PWB scale before and after MBSR participation. PWB change was used as the predictive regressor for changes in gray matter density within those brain regions that had previously shown pre- to post-MBSR changes. Results showed that scores on five PWB subscales as well as the PWB total score increased significantly over the MBSR course. The change was positively correlated with gray matter concentration increases in two symmetrically bilateral clusters in the brainstem. Those clusters appeared to contain the area of the pontine tegmentum, locus coeruleus, nucleus raphe pontis, and the sensory trigeminal nucleus. No clusters were negatively correlated with the change in PWB. This preliminary study suggests a neural correlate of enhanced PWB. The identified brain areas include the sites of synthesis and release of the neurotransmitters, norepinephrine and serotonin, which are involved in the modulation of arousal and mood, and have been related to a variety of affective functions as well as associated clinical dysfunctions.

Is deep brain stimulation a treatment option for anorexia nervosa?

Anorexia nervosa (AN) is a severe psychiatric disorder with high rates of morbidity, comorbidity and mortality, which in a subset of patients (21%) takes on a chronic course. Since an evidence based treatment for AN is scarce, it is crucial to investigate new treatment options, preferably focused on influencing the underlying neurobiological mechanisms of AN. The objective of the present paper was to review the evidence for possible neurobiological correlates of AN, and to hypothesize about potential targets for Deep brain stimulation (DBS) as a treatment for chronic, therapy-refractory AN. One avenue for exploring new treatment options based on the neurobiological correlates of AN, is the search for symptomatologic and neurobiologic parallels between AN and other compulsivity- or reward-related disorders. As in other compulsive disorders, the fronto-striatal circuitry, in particular the insula, the ventral striatum (VS) and the prefrontal, orbitofrontal, temporal, parietal and anterior cingulate cortices, are likely to be implicated in the neuropathogenesis of AN. In this paper we will review the few available cases in which DBS has been performed in patients with AN (either as primary diagnosis or as comorbid condition). Given the overlap in symptomatology and neurocircuitry between reward-related disorders such as obsessive compulsive disorder (OCD) and AN, and the established efficacy of accumbal DBS in OCD, we hypothesize that DBS of the nucleus accumbens (NAc) and other areas associated with reward, e.g. the anterior cingulated cortex (ACC), might be an effective treatment for patients with chronic, treatment refractory AN, providing not only weight restoration, but also significant and sustained improvement in AN core symptoms and associated comorbidities and complications. Possible targets for DBS in AN are the ACC, the ventral anterior limb of the capsula interna (vALIC) and the VS. We suggest conducting larger efficacy studies that also explore the functional effects of DBS in AN.

Clinical pharmacology of eating and not eating

FDA approval of Belviq and Qsymia seems to suggest that novel pharmacological targets to modulate human abnormal eating behaviours are still to be identified. However, a renewed translational approach opens new avenues on eating disorders and female vulnerability, highlighting the role of our reward pathway in obesity and binge eating and leading to potential novel targets. Nevertheless, the 'food addiction' hypothesis is still causing much scientific debate. In this context the interest in the modulation of ghrelin pathway is still very high although, so far, only ghrelin agonism has confirmed its therapeutic potential in cachectic patients. Unfortunately, ghrelin modulation does not offer a therapeutic option for Anorexia Nervosa, where novel promising pharmacological treatments are still to be uncovered.

Convergent dysregulation of frontal cortical cognitive and reward systems in eating disorders

A substantive literature has drawn a compelling case for the functional involvement of mesolimbic/prefrontal cortical neural reward systems in normative control of eating and in the etiology and persistence of severe eating disorders that affect diverse human populations. Presently, we provide a short review that develops an equally compelling case for the importance of dysregulated frontal cortical cognitive neural networks acting in concert with regional reward systems in the regulation of complex eating behaviors and in the presentation of complex pathophysiological symptoms associated with major eating disorders. Our goal is to highlight working models of major eating disorders that incorporate complementary approaches to elucidate functionally interactive neural circuits defined by their regulatory neurochemical phenotypes. Importantly, we also review evidence-based linkages between widely studied psychiatric and neurodegenerative syndromes (e.g., autism spectrum disorders and Parkinson’s disease) and co-morbid eating disorders to elucidate basic mechanisms involving dopaminergic transmission and its regulation by endogenously expressed morphine in these same cortical regions.

Tandospirone, a 5-HT1A partial agonist is effective in treating anorexia nervosa: a case series

This case report details the therapeutic effects of tandospirone on two patients with anorexia nervosa, one with the restricting subtype (ANR), and another with the binge-eating/purging subtype (ANBP). A 22-year-old female patient with ANR and a 23-year-old female patient with ANBP were treated successfully with the 5-HT1A partial agonist tandospirone. After treatment, not only did both patients gain weight, they also showed improved scores on the Eating Disorder Examination Questionnaire. In addition, a 6-month follow-up showed maintenance of these effects. In this disorder, tandospirone may be an effective drug for long-term use with good patient compliance.

Nothing tastes as good as skinny feels: the neurobiology of anorexia nervosa

Individuals with anorexia nervosa (AN) engage in relentless restrictive eating and often become severely emaciated. Because there are no proven treatments, AN has high rates of relapse, chronicity, and death. Those with AN tend to have childhood temperament and personality traits, such as anxiety, obsessions, and perfectionism, which may reflect neurobiological risk factors for developing AN. Restricted eating may be a means of reducing negative mood caused by skewed interactions between serotonin aversive or inhibitory and dopamine reward systems. Brain imaging studies suggest that altered eating is a consequence of dysregulated reward and/or awareness of homeostatic needs, perhaps related to enhanced executive ability to inhibit incentive motivational drives. An understanding of the neurobiology of this disorder is likely to be important for developing more effective treatments.

Advances in the diagnosis of anorexia nervosa and bulimia nervosa using brain imaging

INTRODUCTION: Anorexia and bulimia nervosa are severe psychiatric disorders and the availability of brain imaging techniques hold promise that those techniques will be useful in clinical practice. AREAS COVERED: In this review I describe currently available brain imaging techniques and focus on the brain imaging methods functional magnetic resonance imaging (fMRI) and positron emission tomography (PET). Those techniques have helped describe alterations in brain circuitry in AN and BN that related to anxiety and reward processing. Novel computational models help further define brain function in relation to particular neurotransmitters. EXPERT OPINION: Brain imaging techniques are exciting methods to learn about brain function and progress has been made to identify in healthy populations brain circuits that code behaviors. These techniques have been used in AN and BN over the past decade and have improved our understanding of brain function in those disorders. Still, human brain imaging is not at a point yet where it could be used diagnostically. However, with the refinement of imaging hardware as well as improved models that describe brain function we will get closer to our aims to not only better understand the neurobiology of those disorders, but predict illness development, treatment response and long term prognosis.

Biodistribution, toxicology, and radiation dosimetry of 5-HT1A-receptor agonist positron emission tomography ligand [11C]CUMI-101

Sprague Dawley rats (10/sex/group) were given a single intravenous (iv) dose of CUMI-101 to determine acute toxicity of CUMI-101 and radiation dosimetry estimations were conducted in baboons with [(11)C]CUMI-101. Intravenous administration of CUMI-101 did not produce overt biologically or toxicologically significant adverse effects except transient hypoactivity immediately after dose in the mid- and high-dose groups, which is not considered to be a dose-limiting toxic effect. No adverse effects were observed in the low-dose group. The no observed adverse effect level (NOAEL) is considered to be 44.05 µg/kg for a single iv dose administration in rats. The maximum tolerated dose (MTD) was estimated to be 881 µg/kg for a single iv dose administration. The Medical Internal Radiation Dose (MIRDOSE) estimates indicate the maximum permissible single-study dosage of [(11)C]CUMI-101 in humans is 52 mCi with testes and urinary bladder as the critical organ for males and females, respectively.

Neural circuits, neurotransmitters, and behavior: serotonin and temperament in bulimic syndromes

In bulimia nervosa (BN), and in related binge-purge syndromes, factors affecting central serotonin (5-hydroxytryptamine, 5-HT) function appear to contribute not only to appetitive dysregulation but also to temperamental and personality manifestations. Drawing upon findings from neurobiological, molecular-genetic, and brain-imaging studies, we present an integrative model of the role of 5-HT function in bulimic syndromes. At the core of our model is a consideration of the ways in which diverse hereditary and environmental influences impact the action of the 5-HT system. We believe that our model helps account for heterogeneous traits seen in the bulimic population, for disproportionate representation of individuals displaying pathological personality traits and exposure to severe environmental stressors, and for interindividual variations as to treatment response.