Acute and long-term effects of psilocybin on energy balance and feeding behavior in mice

Effects of psilocybin on body weight, body composition, and metabolites in male and female mice

There is growing interest in the therapeutic potential of psilocybin for the treatment of a wide variety of medical problems, and even for the promotion of wellbeing among healthy individuals. Interestingly, among the many proposed indications, both obesity and anorexia nervosa (AN) have been discussed. However, the effect of psilocybin on appetitive behavior and metabolism is not well known. Here, we report the effects of psilocybin on body weight, intake and output, body composition, and metabolic function among lean male and female wild-type mice. In the days immediately following treatment, both male and female mice receiving a single intraperitoneal dose of psilocybin were consistently heavier than saline controls, with no effect of psilocybin on intake or output. Co-administration of the 5-HT2A/2C receptor antagonist ketanserin had no effect on this outcome. Body composition analysis revealed that psilocybin significantly increased lean and water mass among males, with a similar trend among females. A metabolic panel revealed increased creatine kinase (CK), aspartate aminotransferase (AST), and chloride among male and female psilocybin treated mice. Together, these findings begin to investigate the potential mechanisms of psilocybin's effects on body weight and metabolic measures. Such understanding will be critical for the safe, efficacious, and well-informed use of psilocybin in clinical and non-clinical settings.

5-Methoxy-2-aminoindane Reverses Diet-Induced Obesity and Improves Metabolic Parameters in Mice: A Potential New Class of Antiobesity Therapeutics

The escalating prevalence of obesity and its related disorders represents a daunting global health challenge. Unfortunately, current pharmacological interventions for obesity remain limited and are often associated with debilitating side effects. Against this backdrop, the psychoactive aminoindane derivative 5-methoxy-2-aminoindane (MEAI) has gained considerable attention for its ability to induce a pleasurable, alcohol-like sensation while curbing alcohol consumption. Given the potential impact of MEAI on food addiction and energy homeostasis, we examined its metabolic efficacy on appetite regulation, obesity, and related comorbidities under acute and chronic settings, utilizing a mouse model of diet-induced obesity (DIO). Our results demonstrated that MEAI treatment significantly reduced DIO-induced overweight and adiposity by preserving lean mass and decreasing fat mass. Additionally, MEAI treatment exhibited positive effects on glycemic control by attenuating DIO-induced hyperglycemia, glucose intolerance, and hyperinsulinemia. Furthermore, MEAI reduced DIO-induced hepatic steatosis by decreasing hepatic lipid accumulation and lowering liver triglyceride and cholesterol levels, primarily by inhibiting de novo lipid synthesis. Metabolic phenotyping revealed that MEAI increased energy expenditure and fat utilization while maintaining food consumption similar to that of the vehicle-treated group. Lastly, MEAI normalized voluntary locomotion actions without any overstimulatory effects. These findings provide compelling evidence for the antiobesity effects of MEAI treatment and call for further preclinical testing. In conclusion, our study highlights the potential of MEAI as a novel therapeutic approach for treating obesity and its associated metabolic disorders, offering hope for the development of new treatment options for this global health challenge.

Psilocybin restrains activity-based anorexia in female rats by enhancing cognitive flexibility: contributions from 5-HT1A and 5-HT2A receptor mechanisms

Psilocybin has shown promise for alleviating symptoms of depression and is currently in clinical trials for the treatment of anorexia nervosa (AN), a condition that is characterised by persistent cognitive inflexibility. Considering that enhanced cognitive flexibility after psilocybin treatment is reported to occur in individuals with depression, it is plausible that psilocybin could improve symptoms of AN by breaking down cognitive inflexibility. A mechanistic understanding of the actions of psilocybin is required to tailor the clinical application of psilocybin to individuals most likely to respond with positive outcomes. This can only be achieved using incisive neurobiological approaches in animal models. Here, we use the activity-based anorexia (ABA) rat model and comprehensively assess aspects of reinforcement learning to show that psilocybin (post-acutely) improves body weight maintenance in female rats and facilitates cognitive flexibility, specifically via improved adaptation to the initial reversal of reward contingencies. Further, we reveal the involvement of signalling through the serotonin (5-HT) 1 A and 5-HT2A receptor subtypes in specific aspects of learning, demonstrating that 5-HT1A antagonism negates the cognitive enhancing effects of psilocybin. Moreover, we show that psilocybin elicits a transient increase and decrease in cortical transcription of these receptors (Htr2a and Htr1a, respectively), and a further reduction in the abundance of Htr2a transcripts in rats exposed to the ABA model. Together, these findings support the hypothesis that psilocybin could ameliorate cognitive inflexibility in the context of AN and highlight a need to better understand the therapeutic mechanisms independent of 5-HT2A receptor binding.

A first characterization of the microbiota-resilience link in swine

BACKGROUND

The gut microbiome plays a crucial role in understanding complex biological mechanisms, including host resilience to stressors. Investigating the microbiota-resilience link in animals and plants holds relevance in addressing challenges like adaptation of agricultural species to a warming environment. This study aims to characterize the microbiota-resilience connection in swine. As resilience is not directly observable, we estimated it using four distinct indicators based on daily feed consumption variability, assuming animals with greater intake variation may face challenges in maintaining stable physiological status. These indicators were analyzed both as linear and categorical variables. In our first set of analyses, we explored the microbiota-resilience link using PERMANOVA, α-diversity analysis, and discriminant analysis. Additionally, we quantified the ratio of estimated microbiota variance to total phenotypic variance (microbiability). Finally, we conducted a Partial Least Squares-Discriminant Analysis (PLS-DA) to assess the classification performance of the microbiota with indicators expressed in classes.

RESULTS

This study offers four key insights. Firstly, among all indicators, two effectively captured resilience. Secondly, our analyses revealed robust relationship between microbial composition and resilience in terms of both composition and richness. We found decreased α-diversity in less-resilient animals, while specific amplicon sequence variants (ASVs) and KEGG pathways associated with inflammatory responses were negatively linked to resilience. Thirdly, considering resilience indicators in classes, we observed significant differences in microbial composition primarily in animals with lower resilience. Lastly, our study indicates that gut microbial composition can serve as a reliable biomarker for distinguishing individuals with lower resilience.

CONCLUSION

Our comprehensive analyses have highlighted the host-microbiota and resilience connection, contributing valuable insights to the existing scientific knowledge. The practical implications of PLS-DA and microbiability results are noteworthy. PLS-DA suggests that host-microbiota interactions could be utilized as biomarkers for monitoring resilience. Furthermore, the microbiability findings show that leveraging host-microbiota insights may improve the identification of resilient animals, supporting their adaptive capacity in response to changing environmental conditions. These practical implications offer promising avenues for enhancing animal well-being and adaptation strategies in the context of environmental challenges faced by livestock populations. Video Abstract.

Psilocybin as a lead candidate molecule in preclinical therapeutic studies of psychiatric disorders: A systematic review

Psilocybin is the main psychoactive compound found in hallucinogenic/magic mushrooms and can bind to both serotonergic and tropomyosin receptor kinase b (TrkB) receptors. Psilocybin has begun to show efficacy for a range of neuropsychiatric conditions, including treatment-resistant depression and anxiety disorders; however, neurobiological mechanisms are still being elucidated. Clinical research has found that psilocybin can alter functional connectivity patterns in human brains, which is often associated with therapeutic outcomes. However, preclinical research affords the opportunity to assess the potential cellular mechanisms by which psilocybin may exert its therapeutic effects. Preclinical rodent models can also facilitate a more tightly controlled experimental context and minimise placebo effects. Furthermore, where there is a rationale, preclinical researchers can investigate psilocybin administration in neuropsychiatric conditions that have not yet been researched clinically. As a result, we have systematically reviewed the knowledge base, identifying 82 preclinical studies which were screened based on specific criteria. This resulted in the exclusion of 44 articles, with 34 articles being included in the main review and another 2 articles included as Supporting Information materials. We found that psilocybin shows promise as a lead candidate molecule for treating a variety of neuropsychiatric conditions, albeit showing the most efficacy for depression. We discuss the experimental findings, and identify possible mechanisms whereby psilocybin could invoke therapeutic changes. Furthermore, we critically evaluate the between-study heterogeneity and possible future research avenues. Our review suggests that preclinical rodent models can provide valid and translatable tools for researching novel psilocybin-induced molecular and cellular mechanisms, and therapeutic outcomes.

Beyond the 5-HT2A Receptor: Classic and Nonclassic Targets in Psychedelic Drug Action

Serotonergic psychedelics, such as psilocybin and LSD, have garnered significant attention in recent years for their potential therapeutic effects and unique mechanisms of action. These compounds exert their primary effects through activating serotonin 5-HT2A receptors, found predominantly in cortical regions. By interacting with these receptors, serotonergic psychedelics induce alterations in perception, cognition, and emotions, leading to the characteristic psychedelic experience. One of the most crucial aspects of serotonergic psychedelics is their ability to promote neuroplasticity, the formation of new neural connections, and rewire neuronal networks. This neuroplasticity is believed to underlie their therapeutic potential for various mental health conditions, including depression, anxiety, and substance use disorders. In this mini-review, we will discuss how the 5-HT2A receptor activation is just one facet of the complex mechanisms of action of serotonergic psychedelics. They also interact with other serotonin receptor subtypes, such as 5-HT1A and 5-HT2C receptors, and with neurotrophin receptors (e.g., tropomyosin receptor kinase B). These interactions contribute to the complexity of their effects on perception, mood, and cognition. Moreover, as psychedelic research advances, there is an increasing interest in developing nonhallucinogenic derivatives of these drugs to create safer and more targeted medications for psychiatric disorders by removing the hallucinogenic properties while retaining the potential therapeutic benefits. These nonhallucinogenic derivatives would offer patients therapeutic advantages without the intense psychedelic experience, potentially reducing the risks of adverse reactions. Finally, we discuss the potential of psychedelics as substrates for post-translational modification of proteins as part of their mechanism of action.

UNRAVELing the synergistic effects of psilocybin and environment on brain-wide immediate early gene expression in mice

The effects of context on the subjective experience of serotonergic psychedelics have not been fully examined in human neuroimaging studies, partly due to limitations of the imaging environment. Here, we administered saline or psilocybin to mice in their home cage or an enriched environment, immunofluorescently-labeled brain-wide c-Fos, and imaged iDISCO+ cleared tissue with light sheet fluorescence microscopy (LSFM) to examine the impact of environmental context on psilocybin-elicited neural activity at cellular resolution. Voxel-wise analysis of c-Fos-immunofluorescence revealed clusters of neural activity associated with main effects of context and psilocybin-treatment, which were validated with c-Fos+ cell density measurements. Psilocybin increased c-Fos expression in subregions of the neocortex, caudoputamen, central amygdala, and parasubthalamic nucleus while it decreased c-Fos in the hypothalamus, cortical amygdala, striatum, and pallidum in a predominantly context-independent manner. To gauge feasibility of future mechanistic studies on ensembles activated by psilocybin, we confirmed activity- and Cre-dependent genetic labeling in a subset of these neurons using TRAP2+/-;Ai14+ mice. Network analyses treating each psilocybin-sensitive cluster as a node indicated that psilocybin disrupted co-activity between highly correlated regions, reduced brain modularity, and dramatically attenuated intermodular co-activity. Overall, our results indicate that main effects of context and psilocybin were robust, widespread, and reorganized network architecture, whereas context×psilocybin interactions were surprisingly sparse.

The zebrafish for preclinical psilocybin research

In this review, we discuss the possible utility of zebrafish in research on psilocybin, a psychedelic drug whose recreational use as well as possible clinical application are gaining increasing interest. First, we review behavioral tests with zebrafish, focussing on anxiety and social behavior, which have particular relevance in the context of psilocybin research. Next, we briefly consider methods of genetic manipulations with which psilocybin's phenotypical effects and underlying mechanisms may be investigated in zebrafish. We briefly review the known mechanisms of psilocybin, and also discuss what we know about its safety and toxicity profile. Last, we discuss examples of how psilocybin may be employed for testing treatment efficacy in preclinical research for affective disorders in zebrafish. We conclude that zebrafish has a promising future in preclinical research on psychedelic drugs.

Systematic Review of Binge Eating Rodent Models for Developing Novel or Repurposing Existing Pharmacotherapies

Recent advances in developing and screening candidate pharmacotherapies for psychiatric disorders have depended on rodent models. Eating disorders are a set of psychiatric disorders that have traditionally relied on behavioral therapies for effective long-term treatment. However, the clinical use of Lisdexamfatamine for binge eating disorder (BED) has furthered the notion of using pharmacotherapies for treating binge eating pathologies. While there are several binge eating rodent models, there is not a consensus on how to define pharmacological effectiveness within these models. Our purpose is to provide an overview of the potential pharmacotherapies or compounds tested in established rodent models of binge eating behavior. These findings will help provide guidance for determining pharmacological effectiveness for potential novel or repurposed pharmacotherapies.

Utility of preclinical models in the study of psilocybin - A comprehensive review

Interest in the therapeutic potential of psilocybin across a broad range of neuropsychiatric disorders is rapidly expanding. Despite promising clinical data and tremendous public enthusiasm, complimentary basic and translational studies - which are critical for advancing our understanding of psilocybin's biological effects and promoting innovation - have been relatively few. As with all work involving the study of complex neuropsychopharmacology, the search for deeper understanding of biological mechanisms, and the need for nuanced behavioral analyses in the context of both normal and diseased states, the roles for preclinical models are clear. A systematic search of the literature identified 57 articles involving the study of psilocybin in preclinical rodent models. A comprehensive review and thematic analysis identified 4 broad areas of investigation - pharmacology, toxicity, effects on disease models, and molecular mechanisms - with pharmacology studies accounting for the majority. Though these papers represent a still remarkably small body of literature, several important conclusions can already be drawn, and several areas of high priority for future work can be identified.

UNRAVELing the synergistic effects of psilocybin and environment on brain-wide immediate early gene expression in mice

The effects of context on the subjective experience of serotonergic psychedelics have not been fully examined in human neuroimaging studies, partly due to limitations of the imaging environment. Here, we administered saline or psilocybin to mice in their home cage or an enriched environment, immunofluorescently-labeled brain-wide c-Fos, and imaged cleared tissue with light sheet microscopy to examine the impact of context on psilocybin-elicited neural activity at cellular resolution. Voxel-wise analysis of c-Fos-immunofluorescence revealed differential neural activity, which we validated with c-Fos + cell density measurements. Psilocybin increased c-Fos expression in the neocortex, caudoputamen, central amygdala, and parasubthalamic nucleus and decreased c-Fos in the hypothalamus, cortical amygdala, striatum, and pallidum. Main effects of context and psilocybin-treatment were robust, widespread, and spatially distinct, whereas interactions were surprisingly sparse.