Verhaltenspharmakologische und metabolische Untersuchungen akuter und chronischer Modulationen des Endocannabinoidsystems der Ratte

Das Endocannabinoidsystem spielt eine große Rolle bei der Regulation verschiedener physiologischer Prozesse, indem es die synaptische Transmission moduliert. Es wird postuliert, dass das Endocannabinoidsystem homöostatisch auf eine Dysregulation von verschiedenen Neurotransmittersystemen reagiert und somit protektiv auf die Entwicklung schizophrener Psychosen wirken kann. Auf der anderen Seite gilt Cannabiskonsum während der Pubertät als Risikofaktor für die Ausbildung einer psychotischen Symptomatik im jungen Erwachsenenalter. Dies ist im Wesentlichen auf den psychotomimetischen Hauptbestandteil von Cannabis sativa, Δ9- Tetrahydrocannabinol (Δ9-THC), zurückzuführen. Der zweite Hauptbestandteil der Pflanze, Cannabidiol, wird hingegen als mögliches Antipsychotikum diskutiert. Der genaue Wirkmechanismus ist allerdings noch nicht gut verstanden. In der vorliegenden Arbeit wurde die Hypothese, dass Cannabidiol das Endocannabinoidsystem moduliert und darüber seine antipsychotische Wirkung entfaltet, überprüft. Zudem wurde untersucht, ob die Modulation des Endocannabinoidsystems über die Inhibition von Endo-cannabinoidabbau oder –aufnahme (Hochregulation der Endocannabinoide) Verhaltensänderungen induziert. Die verhaltenspharmakologischen Untersuchungen ergaben, dass bei adulten Ratten unter weitestgehend stressfreien Haltungs- und Testbedingungen die Hochregulation der Endocannabinoidkonzentration keine Auswirkung auf das Verhalten hat. Zudem stellte sich heraus, dass die beim Menschen wirksame Cannabidiol-Menge nicht ausreicht, um auch bei der Ratte adäquate Spiegel im Gehirngewebe zu erreichen. Die chronische pubertäre Behandlung mit dem synthetischen Cannabinoid WIN 55,212-2 gilt als etabliertes Tiermodell für Schizophrenie bei Ratten. Im Rahmen dieser Arbeit wurde untersucht, ob sich dieses Modell auch mit dem vom Menschen konsumierten Δ9-THC reproduzieren lässt, und in wie weit die Darreichungsform die Wirkung der Cannabinoide beeinflussen kann. Die pubertäre Applikation von Δ9-THC in einer öligen Darreichungsform resultierte nicht in langfristigen Verhaltensdefiziten. Außerdem wurde dessen Wirkung auf die Glukoseutilisation während einer Verhal-tensaufgabe mittels Positronen-Emissions-Tomographie (Verhaltens-PET) untersucht. Das Verhaltens-PET stellte sich im Hinblick auf Tiermodellstudien als eine geeignete Methode heraus, jedoch konnten in dieser Arbeit keine metabolischen Veränderungen festgestellt werden. Allerdings zeigte sich, dass die Wirkung des Δ9-THC auf das Verhalten der Tiere durch die Darreichungsform beeinflusst wird, wobei eine schnelle Kinetik, die durch eine wässrige Formulierung erreicht wird, entscheidender zu sein scheint als die im Gehirngewebe erreichte Endkonzentration. Diese Arbeit verdeutlicht die Komplexität des Endocannabinoidsystems sowie des psy-chiatrischen Tiermodells. Wie die heterogenen Ergebnissen in der Literatur zeigen, ist das Tiermodell durch unterschiedlichste Faktoren wie Haltungsbedingungen, Stress oder die Darreichungsform des Cannabinoids sehr beeinflussbar. Mit dem Verhaltens-PET steht eine neue Methode zur Verfügung, mit der zerebrale Regulationsmechanismen des Endocannabinoidsystems sichtbar gemacht werden können, die sich nicht zwangsläufig einheitlich phänotypisch äußern

Plasma endocannabinoids in cocaine dependence and their interaction with cocaine craving and metabotropic glutamate receptor 5 density in the human brain

Animal models indicate that the endocannabinoid system (ECS) plays a modulatory role in stress and reward processing, both crucially impaired in addictive disorders. Preclinical findings showed endocannabinoid-modulated synaptic plasticity in reward brain networks linked to the metabotropic-glutamate-5 receptor (mGluR5), contributing to drug-reinforcing effects and drug-seeking behavior. Although animal models postulate a link between ECS and cocaine addiction, human translational studies are lacking. Here, we tested previous preclinical findings by investigating plasma endocannabinoids (eCBs) anandamide (AEA), 2-arachidonoylglycerol (2-AG), and the related N-acylethanolamines (NAEs) palmitoylethanolamide (PEA) and oleoylethanolamide (OEA), including their interaction with cerebral mGluR5, in chronic cocaine users (CU). We compared basal plasma concentrations between chronic CU (N=103; 69 recreational CU and 34 dependent CU) and stimulant-naïve healthy controls (N=92). Follow-up basal eCB/NAE plasma levels after 12 months were used for reliability and stability check (CU: N=33; controls: N=43). In an additional analysis using$^{11}$C-ABP688 positron emission tomography (PET) in a male subsample (CU: N=18; controls: N=16), we investigated the relationships between eCBs/NAEs and mGluR5 density in the brain. We found higher 2-AG plasma levels in dependent CU compared to controls and recreational CU. 2-AG levels were stable over time across all groups. In the PET-subsample, a positive association between 2-AG and mGluR5 brain density only in CU was found. Our results corroborate animal findings suggesting an alteration of the ECS in cocaine dependence and an association between peripheral 2-AG levels and cerebral mGluR5 in humans. Therefore, the ECS might be a promising pharmaco-therapeutic target for novel treatments of cocaine dependence

Plasma endocannabinoids in cocaine dependence and their relation to cerebral metabotropic glutamate receptor 5 density

Animal models indicate that the endocannabinoid system (ECS) plays a modulatory role in stress and reward processing, both crucially impaired in addictive disorders. Preclinical findings showed endocannabinoid-modulated synaptic plasticity in reward brain networks linked to the metabotropic-glutamate-5 receptor (mGluR5), contributing to drug-reinforcing effects and drug-seeking behavior. Although animal models postulate a link between ECS and cocaine addiction, human translational studies are lacking. Here, we tested previous preclinical findings by investigating plasma endocannabinoids (eCBs) anandamide (AEA), 2-arachidonoylglycerol (2-AG), and the related N-acylethanolamines (NAEs) palmitoylethanolamide (PEA) and oleoylethanolamide (OEA), including their interaction with cerebral mGluR5, in chronic cocaine users (CU). We compared basal plasma concentrations between chronic CU (N = 103; 69 recreational CU and 34 dependent CU) and stimulant-naïve healthy controls (N = 92). Follow-up basal eCB/NAE plasma levels after 12 months were used for reliability and stability check (CU: N = 33; controls: N = 43). In an additional analysis using $^{11}$C-ABP688 positron emission tomography (PET) in a male subsample (CU: N = 18; controls: N = 16), we investigated the relationships between eCBs/NAEs and mGluR5 density in the brain. We found higher 2-AG plasma levels in dependent CU compared to controls and recreational CU. 2-AG levels were stable over time across all groups. In the PET-subsample, a positive association between 2-AG and mGluR5 brain density only in CU was found. Our results corroborate animal findings suggesting an alteration of the ECS in cocaine dependence and an association between peripheral 2-AG levels and cerebral mGluR5 in humans. Therefore, the ECS might be a promising pharmaco-therapeutic target for novel treatments of cocaine dependence

A common molecular mechanism for cognitive deficits and craving in alcoholism

Alcohol-dependent patients commonly show impairments in executive functions that facilitate craving and can lead to relapse. The medial prefrontal cortex, a key brain region for executive control, is prone to alcohol-induced neuroadaptations. However, the molecular mechanisms leading to executive dysfunction in alcoholism are poorly understood. Here using a bi-directional neuromodulation approach we demonstrate a causal link for reduced prefrontal mGluR2 function and both impaired executive control and alcohol craving. By neuron-specific prefrontal knockdown of mGluR2 in rats, we generated a phenotype of reduced cognitive flexibility and excessive alcohol-seeking. Conversely, restoring prefrontal mGluR2 levels in alcohol-dependent rats rescued these pathological behaviors. Also targeting mGluR2 pharmacologically reduced relapse behavior. Finally, we developed a FDG-PET biomarker to identify those individuals that respond to mGluR2-based interventions. In conclusion, we identified a common molecular pathological mechanism for both executive dysfunction and alcohol craving, and provide a personalized mGluR2-mechanism-based intervention strategy for medication development of alcoholism

EMPOWERED trial: protocol for a randomised control trial of digitally supported, highly personalised and measurement-based care to improve functional outcomes in young people with mood disorders

Objectives: Many adolescents and young adults with emerging mood disorders do not achieve substantial improvements in education, employment, or social function after receiving standard youth mental health care. We have developed a new model of care referred to as ‘highly personalised and measurement-based care’ (HP&MBC). HP&MBC involves repeated assessment of multidimensional domains of morbidity to enable continuous and personalised clinical decision-making. Although measurement-based care is common in medical disease management, it is not a standard practice in mental health. This clinical effectiveness trial tests whether HP&MBC, supported by continuous digital feedback, delivers better functional improvements than standard care and digital support. Method and analysis: This controlled implementation trial is a PROBE study (Prospective, Randomised, Open, Blinded End-point) that comprises a multisite 24-month, assessor-blinded, follow-up study of 1500 individuals aged 15–25 years who present for mental health treatment. Eligible participants will be individually randomised (1:1) to 12 months of HP&MBC or standardised clinical care. The primary outcome measure is social and occupational functioning 12 months after trial entry, assessed by the Social and Occupational Functioning Assessment Scale. Clinical and social outcomes for all participants will be monitored for a further 12 months after cessation of active care. Ethics and dissemination: This clinical trial has been reviewed and approved by the Human Research Ethics Committee of the Sydney Local Health District (HREC Approval Number: X22-0042 & 2022/ETH00725, Protocol ID: BMC-YMH-003-2018, protocol version: V.3, 03/08/2022). Research findings will be disseminated through peer-reviewed journals, presentations at scientific conferences, and to user and advocacy groups. Participant data will be deidentified. Trial registration number: ACTRN12622000882729

The Functional Networks of Prepulse Inhibition: Neuronal Connectivity Analysis Based on FDG-PET in Awake and Unrestrained Rats

Prepulse inhibition (PPI) is a neuropsychological process during which a weak sensory stimulus (“prepulse”) attenuates the motor response (“startle reaction”) to a subsequent strong startling stimulus. It is measured as a surrogate marker of sensorimotor gating in patients suffering from neuropsychological diseases such as schizophrenia, as well as in corresponding animal models. A variety of studies has shown that PPI of the acoustical startle reaction comprises three brain circuitries for: (i) startle mediation, (ii) PPI mediation, and (iii) modulation of PPI mediation. While anatomical connections and information flow in the startle and PPI mediation pathways are well known, spatial and temporal interactions of the numerous regions involved in PPI modulation are incompletely understood. We therefore combined [18F]fluoro-2-deoxyglucose positron-emission-tomography (FDG-PET) with PPI and resting state control paradigms in awake rats. A battery of subtractive, correlative as well as seed-based functional connectivity analyses revealed a default mode-like network (DMN) active during resting state only. Furthermore, two functional networks were observed during PPI: Metabolic activity in the lateral circuitry was positively correlated with PPI effectiveness and involved the auditory system and emotional regions. The medial network was negatively correlated with PPI effectiveness, i.e., associated with startle, and recruited a spatial/cognitive network. Our study provides evidence for two distinct neuronal networks, whose continuous interplay determines PPI effectiveness in rats, probably by either protecting the prepulse or facilitating startle processing. Discovering similar networks affected in neuropsychological disorders may help to better understand mechanisms of sensorimotor gating deficits and provide new perspectives for therapeutic strategies

Cannabinoids and the endocannabinoid system in anxiety, depression, and dysregulation of emotion in humans

Purpose of review This review is to summarize most recent evidence published in the last 18 months on medical and recreational use of cannabis and cannabinoids in relation to anxiety, depression (unipolar and bipolar), and dysregulation of emotions as part of posttraumatic stress disorders (PTSD) and emotionally instable personality disorders. It also covers the investigation of endocannabinoids as potential biomarkers in these conditions. This is important with increasing medicinal use of cannabinoids and growing social tolerance towards recreational cannabis use. Recent findings There is some recent evidence suggesting cannabinoids, cannabidiol or cannabidiol-enriched cannabis preparations have anxiolytic properties. In addition, depression may be worsened by cannabis use, however, randomized controlled trials (RCT) are lacking. New evidence also suggests that cannabidiol or cannabidiol-enriched cannabis use for PTSD and emotion regulation can induce hyporesponse to fear and stress. Further, several lines of evidence point to the endocannabinoid system as a key player in some of the reviewed disorders, in particular anxiety and PTSD. The most recent evidence for a therapeutic use of cannabinoids in the reviewed conditions is weak and lacking well designed RCTs. However, there is some indication of the role of the endocannabinoid system in these conditions that warrant further studies

Cannabidiol as a potential new type of an antipsychotic. A critical review of the evidence

There is urgent need for the development of mechanistically different and less side-effect prone antipsychotic compounds. The endocannabinoid system has been suggested to represent a potential new target in this indication. While the chronic use of cannabis itself has been considered a risk factor contributing to the development of schizophrenia, triggered by the phytocannabinoid delta-9-tetrahydrocannabinol (Δ9 THC), cannabidiol, the second most important phytocannabinoid, appears to have no psychotomimetic potential. Although results from animal studies are inconsistent to a certain extent and seem to depend on behavioral paradigms, treatment duration and experimental conditions applied, cannabidiol has shown antipsychotic properties in rodents and rhesus monkeys. After some individual treatment attempts, the first randomized, double-blind controlled clinical trial had been conducted and demonstrated that cannabidiol exerts antipsychotic properties in acute schizophrenia comparable to the antipsychotic drug amisulpride accompanied by a superior, placebo-like side effect profile. As the clinical improvement by cannabidiol was significantly associated with elevated anandamide levels, it appears likely that its antipsychotic action is based on mechanisms associated with increased anandamide concentrations. However, a plethora of mechanisms of action has been suggested, but their potential relevance for the antipsychotic effects of cannabidiol needs still to be investigated. The clarification of these mechanisms as well as the establishment of cannabidiol’s antipsychotic efficacy and its hopefully benign side-effect profile remains the subject of a number of previously started clinical trials

Different pharmaceutical preparations of Delta(9)-tetrahydrocannabinol differentially affect its behavioral effects in rats

Based on the contribution of the endocannabinoid system to the pathophysiology of schizophrenia, the primary pro-psychotic ingredient of Cannabis sativa, Delta-9-tetrahydrocannabinol (Delta-9-THC), is used in preclinical as well as clinical research to mimic schizophrenia-like symptoms. While it is common to administer lipid-based formulations of Delta-9-THC in human studies orally, intraperitoneal injections of water-based solutions are used in animal models. Because of the poor water solubility of Delta-9-THC, solubilizers such as ethanol and/or emulsifiers are needed for these preparations. In order to test whether a lipid-based solvent would be superior over a water-based vehicle in rats, we compared the effects on locomotor activity and prepulse inhibition (PPI) of the acoustic startle reaction, as well as pharmacokinetic data obtained from rats' serum and brain tissue samples. Up to 50 mg/kg Delta-9-THC in the lipid-based formulation was not able to induce any behavioral alterations, while already 5 mg/kg of the water-based Delta-9-THC preparation significantly reduced locomotor activity. This also induced a small but significant PPI reduction, which was prepulse intensity dependent. Interestingly, the reflexive motor response to the startle stimulus was not affected by the water-based Delta-9-THC solution. Analysis of serum and brain Delta-9-THC levels by high-performance liquid chromatography/mass spectrometry revealed that although the final concentration reached in the brain was comparable for both pharmaceutical preparations, the water-based formulation achieved a faster kinetic. We, therefore, conclude that the slope of the Delta-9-THC concentration-time curve and the resulting cannabinoid receptor type 1 activation per time unit are responsible for the induction of behavioral alterations