Cannabidiol disrupts the consolidation of specific and generalized fear memories via dorsal hippocampus CB 1 and CB 2 receptors

Cannabidiol (CBD) potentiates physiological and behavioral markers of hypothalamic-pituitary-adrenal (HPA) axis responsivity in female and male mice

RATIONALE

Clinical literature indicates there may be a therapeutic use of cannabidiol (CBD) for stress-related disorders. Preclinical literature remains conflicted regarding the underlying neurobehavioral mechanisms, reporting mixed effects of CBD (increased, decreased, or no effect) on anxiety- and fear-related behaviors. Preclinical data demonstrated that CBD modulates hypothalamus-pituitary-adrenal (HPA) axis gene expression; it is unknown whether CBD changes HPA axis responsivity and how this relates to altered behavior.

OBJECTIVES

We aimed to evaluate whether acute or chronic CBD administration would alter physiological and behavioral measures of HPA axis responsivity in male or female mice.

METHODS

C57BL/6 mice of both sexes were injected with vehicle or CBD (30 mg/kg, i.p.) daily for 26 days. Plasma corticosterone (CORT) levels were evaluated following dexamethasone suppression and adrenocorticotropin hormone stimulation tests after acute and chronic CBD exposure. After chronic CBD, mice were tested for anxiety-like behavior using an elevated plus maze (EPM) and associative fear learning and memory using a trace fear conditioning (FC) protocol.

RESULTS

Compared to vehicle, CBD induced a state of HPA axis hyperactivation, an effect which was significant in males; it also normalized anxiety-like behavior in female mice classified as having HPA axis hypofunction and primed all female mice for enhanced conditioned responding. Significant sex differences were also detected: females had greater plasma CORT levels and HPA axis responsivity than males, exhibited less EPM anxiety-like behavior, and were more responsive during FC.

CONCLUSIONS

CBD potentiated physiological and behavioral markers of HPA axis function and normalized anxiety-like behavior in a sex-specific manner. This observation has implications for cannabinoid-based drug development targeting individuals with stress-related disorders involving HPA axis hypofunction pathology.

Guilu Erxian Jiao remodels dendritic spine morphology through activation of the hippocampal TRPC6-CaMKIV-CREB signaling pathway and suppresses fear memory generalization in rats with post-traumatic stress disorder

ETHNOPHARMACOLOGICAL RELEVANCE

Guilu Erxian Jiao (GLEXJ) is a renowned traditional Chinese herbal formula used to tonify the kidney. It is employed to treat psychiatric disorders, and alleviate memory impairment, cognitive dysfunction, and behavioral disorders. Modern pharmacological studies have demonstrated GLEXJ's ability to significantly inhibit the fear response in post-traumatic stress disorder (PTSD) and facilitate the extinction of fear memory. However, the underlying pharmacological mechanisms remain elusive.

AIM OF THE STUDY

Fear memory generalization, a fundamental characteristic of PTSD, remains poorly understood, and optimal pharmacological treatments are lacking. This study aimed to investigate GLEXJ's inhibitory effects on fear memory generalization in PTSD rats and elucidate its underlying mechanisms.

MATERIALS AND METHODS

PTSD rats were induced using the single prolonged stress and electrical stimulation (SPS&S) protocol and treated with GLEXJ or paroxetine (PRX). Fear memory generalization was assessed using a contextual fear memory test. Hippocampal dendritic spine morphology was analyzed using Golgi-Cox staining. The chemical composition of GLEXJ was determined using ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). Network pharmacology was employed to predict GLEXJ's therapeutic mechanism in PTSD treatment. Western blotting and immunofluorescence were used to measure indicators of the transient receptor potential channel 6 (TRPC6)-mediated calcium/calmodulin-dependent protein kinase IV-cAMP response element-binding protein (CaMKIV-CREB) signaling pathway. In vitro, TRPC6 was suppressed in rat adrenal pheochromocytoma (PC12) cells using lentiviral vectors, and phalloidin staining was employed to examine changes in Fibros actin (F-actin), elucidating the mechanistic effects of GLEXJ-containing serum.

RESULTS

GLEXJ significantly mitigated fear memory generalization in PTSD rats, even with repeated stress exposure. It also alleviated abnormal hippocampal dendritic spine morphology. Network pharmacology analysis confirmed that GLEXJ was closely related to the Ca2+ signaling pathway in PTSD treatment. PTSD rats exhibited disrupted TRPC6-mediated CaMKIV-CREB signaling and impaired synaptic plasticity. GLEXJ upregulated TRPC6 expression, reactivated the CaMKIV-CREB pathway, and promoted synaptic remodeling. In vitro studies confirmed that TRPC6 suppression reduced F-actin levels while GLEXJ-containing serum increased TRPC6 expression and F-actin content.

CONCLUSIONS

GLEXJ activates CaMKIV-CREB signaling by upregulating TRPC6 in the hippocampus of PTSD rats, leading to the positive modulation of dendritic spine morphology and synaptic remodeling. This mechanism contributes to the attenuation of fear memory generalization. Given the limitations of current PTSD treatments, these findings offer potential avenues for developing more effective therapeutic strategies.

Therapeutic potential of minor cannabinoids in psychiatric disorders: A systematic review

Interest in cannabinoids' therapeutic potential in mental health is growing, supported by evidence of the involvement of the endocannabinoid system in psychiatric disorders such as anxiety, depression, and addiction. While the major cannabinoids cannabidiol (CBD) and Δ9-tetrahydrocannabinol (Δ9-THC) have been more extensively researched, approximately 120 minor cannabinoids from the cannabis plant have been identified. Although some displayed promising pharmacological profiles, research on their application for psychiatric disorders is fragmented. This systematic review evaluates, for the first time, both preclinical and clinical studies exploring minor cannabinoids' therapeutic potential in psychiatric disorders. 22 preclinical studies and one clinical study were included, investigating various minor cannabinoids in substance use disorders, anxiety disorders, depressive disorders, trauma and stressor-related disorders, psychotic disorders, neurodevelopmental disorders, and eating disorders. Despite the heterogeneous results and the moderate to high risk of bias in several articles, certain compounds demonstrate promise for further investigation. Δ8-tetrahydrocannabidivarin (Δ8-THCV) exhibited potential for nicotine addiction; Δ9-tetrahydrocannabidivarin (Δ9-THCV) for psychotic-like symptoms; cannabidiolic acid methyl ester (CBDA-ME) alleviated anxiety and depression-like symptoms, and cannabidivarin (CBDV) autism spectrum disorder-like symptoms.

Interplay between endocannabinoid and endovanilloid mechanisms in fear conditioning

OBJECTIVE

The transient receptor potential cation channel, subfamily V (vanilloid), member 1 (TRPV1) mediates pain perception to thermal and chemical stimuli in peripheral neurons. The cannabinoid receptor type 1 (CB1), on the other hand, promotes analgesia in both the periphery and the brain. TRPV1 and CB1 have also been implicated in learned fear, which involves the association of a previously neutral stimulus with an aversive event. In this review, we elaborate on the interplay between CB1 receptors and TRPV1 channels in learned fear processing.

METHODS

We conducted a PubMed search for a narrative review on endocannabinoid and endovanilloid mechanisms on fear conditioning.

RESULTS

TRPV1 and CB1 receptors are activated by a common endogenous agonist, arachidonoyl ethanolamide (anandamide), Moreover, they are expressed in common neuroanatomical structures and recruit converging cellular pathways, acting in concert to modulate fear learning. However, evidence suggests that TRPV1 exerts a facilitatory role, whereas CB1 restrains fear responses.

CONCLUSION

TRPV1 and CB1 seem to mediate protective and aversive roles of anandamide, respectively. However, more research is needed to achieve a better understanding of how these receptors interact to modulate fear learning.

Cannabidiol modulates contextual fear memory consolidation in animals with experimentally induced type-1 diabetes mellitus

OBJECTIVES

In view of the neuroprotective characteristic of cannabidiol (CBD) and its beneficial action on aversive memory in non-diabetic animals, we aimed to investigate in animals with experimentally induced type-1 diabetes mellitus (T1DM) whether CBD treatment would be able to impair the contextual fear memory consolidation, its generalisation and whether the effect would be lasting. We also investigated the CBD effect on anxiety-like responses.

METHODS

After T1DM induction, animals received single or more prolonged treatment with CBD and were submitted to the contextual fear conditioning test. As expression of activity-regulated cytoskeletal-associated (Arc) protein is necessary for memory consolidation, we evaluated its expression in the dorsal hippocampus (DH). For evaluating anxiety-related responses, animals were submitted to the elevated plus maze test (EPMT), in which the time and number of entries in the open arms were used as anxiety index.

RESULTS

A single injection of CBD impaired the contextual fear memory consolidation and its generalisation, which was evaluated by exposing the animal in a neutral context. This single injection was able to reduce the elevated expression of Arc in the DH from these animals. Interestingly, more prolonged treatment with CBD also impaired the persistence of context-conditioned fear memory and induced an anxiolytic-like effect, as the treated group spent more time in the open arms of the EPMT.

CONCLUSION

CBD interferes with contextual fear memory and the dosage regimen of treatment seems to be important. Moreover, we cannot rule out the involvement of emotional aspects in these processes related to fear memory.

Cannabidiol enhances socially transmitted food preference: a role of acetylcholine in the mouse basal forebrain

RATIONALE AND OBJECTIVE

Rodents acquire food information from their conspecifics and display a preference for the conspecifics' consumed food. This social learning of food information from others promotes the survival of a species, and it is introduced as the socially transmitted food preference (STFP) task. The cholinergic system in the basal forebrain plays a role in the acquisition of STFP. Cannabidiol (CBD), one of the most abundant phytocannabinoids, exerts its therapeutic potential for cognitive deficits through versatile mechanisms of action, including its interaction with the cholinergic system. We hypothesize a positive relationship between CBD and STFP because acetylcholine (ACh) is involved in STFP, and CBD increases the ACh levels in the basal forebrain.

MATERIALS AND METHODS

Male C57BL/6J mice were trained to acquire the STFP task. We examined whether CBD affects STFP memory by administering CBD (20 mg/kg, i.p.) before the STFP social training. The involvement of cholinergic system in CBD's effect on STFP was examined by knockdown of brain acetylcholinesterase (AChE), applying a nonselective muscarinic antagonist SCO (3 mg/kg, i.p.) before CBD treatment, and measuring the basal forebrain ACh levels in the CBD-treated mice.

RESULTS

We first showed that CBD enhanced STFP memory. Knockdown of brain AChE also enhanced STFP memory, which mimicked CBD's effect on STFP. SCO blocked CBD's memory-enhancing effect on STFP. Our most significant finding is that the basal forebrain ACh levels in the CBD-treated mice, but not their control counterparts, were positively correlated with mice's STFP memory performance.

CONCLUSION

This study indicates that CBD enhances STFP memory in mice. Specifically, those which respond to CBD by increasing the muscarinic-mediated ACh signaling perform better in their STFP memory.

Cannabidiol effects on fear processing and implications for PTSD: Evidence from rodent and human studies

Cannabidiol (CBD) modulates aversive memory and its extinction, with potential implications for treating anxiety- and stress-related disorders. Here, we summarize and discuss scientific evidence showing that CBD administered after the acquisition (consolidation) and retrieval (reconsolidation) of fear memory attenuates it persistently in rats and mice. CBD also reduces fear expression and enhances fear extinction. These effects involve the activation of cannabinoid type-1 (CB1) receptors in the dorsal hippocampus, bed nucleus of stria terminalis, and medial prefrontal cortex, comprising the anterior cingulate, prelimbic, and infralimbic subregions. Serotonin type-1A (5-HT1A) receptors also mediate some CBD effects on fear memory. CBD effects on fear memory acquisition vary, depending on the aversiveness of the conditioning procedure. While rodent findings are relatively consistent and encouraging, human studies investigating CBD's efficacy in modulating aversive/traumatic memories are still limited. More studies are needed to investigate CBD's effects on maladaptive, traumatic memories, particularly in post-traumatic stress disorder patients.

Cannabidiol ameliorates PTSD-like symptoms by inhibiting neuroinflammation through its action on CB2 receptors in the brain of male mice

Post-traumatic stress disorder (PTSD) is a debilitating mental health disease related to traumatic experience, and its treatment outcomes are unsatisfactory. Accumulating research has indicated that cannabidiol (CBD) exhibits anti-PTSD effects, however, the underlying mechanism of CBD remains inadequately investigated. Although many studies pertaining to PTSD have primarily focused on aberrations in neuronal functioning, the present study aimed to elucidate the involvement and functionality of microglia/macrophages in PTSD while also investigated the modulatory effects of CBD on neuroinflammation associated with this condition. We constructed a modified single-prolonged stress (SPS) mice PTSD model and verified the PTSD-related behaviors by various behavioral tests (contextual freezing test, elevated plus maze test, tail suspension test and novel object recognition test). We observed a significant upregulation of Iba-1 and alteration of microglial/macrophage morphology within the prefrontal cortex and hippocampus, but not the amygdala, two weeks after the PTSD-related stress, suggesting a persistent neuroinflammatory phenotype in the PTSD-modeled group. CBD (10 mg/kg, i.p.) inhibited all PTSD-related behaviors and reversed the alterations in both microglial/macrophage quantity and morphology when administered prior to behavioral assessments. We further found increased pro-inflammatory factors, decreased PSD95 expression, and impaired synaptic density in the hippocampus of the modeled group, all of which were also restored by CBD treatment. CBD dramatically increased the level of anandamide, one of the endocannabinoids, and cannabinoid type 2 receptors (CB2Rs) transcripts in the hippocampus compared with PTSD-modeled group. Importantly, we discovered the expression of CB2Rs mRNA in Arg-1-positive cells in vivo and found that the behavioral effects of CBD were diminished by CB2Rs antagonist AM630 (1 mg/kg, i.p.) and both the behavioral and molecular effects of CBD were abolished in CB2Rs knockout mice. These findings suggest that CBD would alleviate PTSD-like behaviors in mice by suppressing PTSD-related neuroinflammation and upregulation and activation of CB2Rs may serve as one of the underlying mechanisms for this therapeutic effect. The present study offers innovative experimental evidence supporting the utilization of CBD in PTSD treatment from the perspective of its regulation of neuroinflammation, and paves the way for leveraging the endocannabinoid system to regulate neuroinflammation as a potential therapeutic approach for psychiatric disorders.

Single-Nucleus Transcriptome Profiling from the Hippocampus of a PTSD Mouse Model and CBD-Treated Cohorts

Post-traumatic stress disorder (PTSD) is the most common psychiatric disorder after a catastrophic event; however, the efficacious treatment options remain insufficient. Increasing evidence suggests that cannabidiol (CBD) exhibits optimal therapeutic effects for treating PTSD. To elucidate the cell-type-specific transcriptomic pathology of PTSD and the mechanisms of CBD against this disease, we conducted single-nucleus RNA sequencing (snRNA-seq) in the hippocampus of PTSD-modeled mice and CBD-treated cohorts. We constructed a mouse model by adding electric foot shocks following exposure to single prolonged stress (SPS+S) and tested the freezing time, anxiety-like behavior, and cognitive behavior. CBD was administrated before every behavioral test. The PTSD-modeled mice displayed behaviors resembling those of PTSD in all behavioral tests, and CBD treatment alleviated all of these PTSD-like behaviors (n = 8/group). Three mice with representative behavioral phenotypes were selected from each group for snRNA-seq 15 days after the SPS+S. We primarily focused on the excitatory neurons (ExNs) and inhibitory neurons (InNs), which accounted for 68.4% of the total cell annotations. A total of 88 differentially upregulated genes and 305 differentially downregulated genes were found in the PTSD mice, which were found to exhibit significant alterations in pathways and biological processes associated with fear response, synaptic communication, protein synthesis, oxidative phosphorylation, and oxidative stress response. A total of 63 overlapping genes in InNs were identified as key genes for CBD in the treatment of PTSD. Subsequent Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses revealed that the anti-PTSD effect of CBD was related to the regulation of protein synthesis, oxidative phosphorylation, oxidative stress response, and fear response. Furthermore, gene set enrichment analysis (GSEA) revealed that CBD also enhanced retrograde endocannabinoid signaling in ExNs, which was found to be suppressed in the PTSD group. Our research may provide a potential explanation for the pathogenesis of PTSD and facilitate the discovery of novel therapeutic targets for drug development. Moreover, it may shed light on the therapeutic mechanisms of CBD.

Cannabidiol effect on long-term brain alterations in septic rats: Involvement of PPARγ activation

Sepsis is a life-threatening condition induced by a deregulated host response to infection. Post-sepsis injury includes long-term cognitive impairment, whose neurobiological mechanisms and effective treatment remain unknown. The present study was designed to determine the potential effects of cannabidiol (CBD) in a sepsis-associated encephalopathy (SAE) model and explore if peroxisome proliferator activated receptor gamma (PPARγ) is the putative mechanism underpinning the beneficial effects. SAE was induced in Wistar rats by cecal ligation and puncture (CLP) or sham (control). CLP rats received vehicle, CBD (10 mg/kg), PPARγ inhibitor (GW9662 - 1 mg/kg), or GW9662 (1 mg/kg) + CBD (10 mg/kg) intraperitoneally for ten days. During this period, the survival rate was recorded, and at the end of 10 days, a memory test was performed, and the prefrontal cortex and hippocampus were removed to verify brain-derived neurotrophic factor (BDNF), cytokines (IL-1β, IL-6 and IL-10), myeloperoxidase activity, nitrite nitrate concentration, and lipid and protein carbonylation and catalase activity. Septic rats presented cognitive decline and an increase in mortality following CLP. Only CBD alone improved the cognitive impairment, which was accompanied by restoration of BDNF, reduced neuroinflammation, and oxidative stress, mainly in the hippocampus. This study shows that CLP induces an increase in brain damage and CBD has neuroprotective effects on memory impairment and neurotrophins, as well as against neuroinflammation and oxidative stress, and is mediated by PPARγ activation.

Decoding the language of fear: Unveiling objective and subjective indicators in rodent models through a systematic review and meta-analysis

While rodent models are vital for studying mental disorders, the underestimation of construct validity of fear indicators has led to limitations in translating to effective clinical treatments. Addressing this gap, we systematically reviewed 5054 articles from the 1960 s, understanding underlying theoretical advancement, and selected 68 articles with at least two fear indicators for a three-level meta-analysis. We hypothesized correlations between different indicators would elucidate similar functions, while magnitude differences could reveal distinct neural or behavioral mechanisms. Our findings reveal a shift towards using freezing behavior as the primary fear indicator in rodent models, and strong, moderate, and weak correlations between freezing and conditioned suppression ratios, 22-kHz ultrasonic vocalizations, and autonomic nervous system responses, respectively. Using freezing as a reference, moderator analysis shows treatment types and fear stages significantly influenced differences in magnitudes between two indicators. Our analysis supports a two-system model of fear in rodents, where objective and subjective fears could operate on a threshold-based mechanism.

Phosphodiesterase 4 inhibition after retrieval switches the memory fate favoring extinction instead of reconsolidation

Phosphodiesterase 4 (PDE4), an enzyme expressed in the dorsal hippocampus (DH), hydrolyzes the cAMP, limiting the PKA-induced CREB phosphorylation (pCREB) and BDNF expression. Depending on the brain region, PKA and pCREB mediate reconsolidation or extinction, whereas BDNF is mainly related to extinction facilitation. The mechanisms underpinning the switch between reconsolidation and extinction are relatively unknown. Here, we tested the hypothesis that PDE4 might control these processes. We showed in Wistar rats submitted to contextual fear conditioning that PDE4 inhibition with roflumilast (ROF) within the DH, after a short retrieval, did not change freezing behavior after one day (TestA1). After 10 days, the ROF-treated group significantly reduced the expression of freezing behavior. This effect depended on retrieval, Test A1 exposure, and reinstated after a remainder foot shock, suggesting an extinction facilitation. The ROF effect depended on PKA after retrieval or, protein synthesis after Test A1. After retrieval, ROF treatment did not change the pCREB/CREB ratio in the DH. It enhanced proBDNF expression without changing pre-proBDNF or mature BDNF in the DH after Test A1. The results suggest that the inhibition of PDE4 in the DH after a short retrieval changes the memory sensibility from reconsolidation to extinction via regulating proBDNF expression.

Involvement of cannabinoid receptors and neuroinflammation in early sepsis: Implications for posttraumatic stress disorder

Sepsis is associated with several comorbidities in survivors, such as posttraumatic stress disorder (PTSD). This study investigated whether rats that survive sepsis develop the generalization of fear memory as a model of PTSD. Responses to interventions that target the endothelin-1 (ET-1)/cannabinoid system and glial activation in the initial stages of sepsis were evaluated. As a control, we evaluated hyperalgesia before fear conditioning. Sepsis was induced by cecal ligation and puncture (CLP) in Wistar rats. CLP-induced sepsis with one or three punctures resulted in fear generalization in the survivors 13 and 20 days after the CLP procedure, a process that was not associated with hyperalgesia. Septic animals were intracerebroventricularly treated with vehicle, the endothelin receptor A (ETA) antagonist BQ123, the cannabinoid CB1 and CB2 receptor antagonists AM251 and AM630, respectively, and the glial blocker minocycline 4 h after CLP. The blockade of either CB1 or ETA receptors increased the survival rate, but only the former reversed fear memory generalization. The endothelinergic system blockade is important for improving survival but not for fear memory. Treatment with the CB2 receptor antagonist or minocycline also reversed the generalization of fear memory but did not increase the survival rate that was associated with CLP. Minocycline treatment also reduced tumor necrosis factor-α levels in the hippocampus suggesting that neuroinflammation is important for the generalization of fear memory induced by CLP. The influence of CLP on the generalization of fear memory was not related to Arc protein expression, a regulator of synaptic plasticity, in the dorsal hippocampus.

Phytotherapy of abnormality of fear memory: A narrative review of mechanisms

It is generally believed that in post-traumatic stress disorder (PTSD), the high expression of fear memory is mainly determined by amygdala hyperactivity and hippocampus hypoactivity. In this review, we firstly updated the mechanisms of fear memory, and then searched the experimental evidence of phytotherapy for fear memory in the past five years. Based on the summary of those experimental studies, we further discussed the future research strategies of plant medicines, including the study of the mechanism of specific brain regions, the optimal time for the prevention and treatment of fear memory-related diseases such as PTSD, and the development of new drugs with active components of plant medicines. Accordingly, plant medicines play a clear role in improving fear memory abnormalities and have the drug development potential in the treatment of fear-related disorders.

Long-Term Treatment with Cannabidiol-Enriched Cannabis Extract Induces Synaptic Changes in the Adolescent Rat Hippocampus

The endocannabinoid system (eCS) is widely distributed in mammalian tissues and it is classically formed by cannabinoid receptors, endogenous bioactive lipids and its synthesis and degradation enzymes. Due to the modulatory role of eCS in synaptic activity in the Central Nervous System (CNS), phytocannabinoids have been increasingly used for the treatment of neurological disorders, even though little is known in terms of the long-term effect of these treatments on CNS development, mainly in the timeframe that comprises childhood and adolescence. Furthermore, an increased number of clinical trials using full-spectrum Cannabis extracts has been seen, rather than the isolated form of phytocannabinoids, when exploring the therapeutical benefits of the Cannabis plant. Thus, this study aims to evaluate the effect of cannabidiol (CBD)-enriched Cannabis extract on synaptic components in the hippocampus of rats from adolescence to early adulthood (postnatal day 45 to 60). Oral treatment of healthy male Wistar rats with a CBD-enriched Cannabis extract (3 mg/kg/day CBD) during 15 days did not affect food intake and water balance. There was also no negative impact on locomotor behaviour and cognitive performance. However, the hippocampal protein levels of GluA1 and GFAP were reduced in animals treated with the extract, whilst PSD95 levels were increased, which suggests rearrangement of glutamatergic synapses and modulation of astrocytic features. Microglial complexity was reduced in CA1 and CA3 regions, but no alterations in their phagocytic activity have been identified by Iba-1 and LAMP2 co-localization. Collectively, our data suggest that CBD-enriched Cannabis treatment may be safe and well-tolerated in healthy subjects, besides acting as a neuroprotective agent against hippocampal alterations related to the pathogenesis of excitatory and astrogliosis-mediated disorders in CNS.

Systemic Chronic Treatment with Cannabidiol in Carioca High- and Low-Conditioned Freezing Rats in the Neuropathic Pain Model: Evaluation of Pain Sensitivity

Studies have shown high comorbidity of anxiety disorder and chronic pain; generalized anxiety disorder (GAD) and neuropathic pain are among these pathologies. Cannabidiol (CBD) has been considered a promising treatment for these conditions. This study investigated whether chronic systemic treatment with CBD alters pain in high- (CHF) and low-freezing (CLF) Carioca rats (GAD model) and control rats (CTL) submitted to chronic neuropathic pain. The rats were evaluated in the sensory aspects (von Frey, acetone, and hot plate tests) before the chronic constriction injury of the ischiatic nerve (CCI) or not (SHAM) and on days 13 and 23 after surgery. Chronic treatment with CBD (5 mg/kg daily) was used for ten days, starting the 14th day after surgery. The open field test on the 22nd also evaluated locomotion and anxiety-like behavior. CBD treatment had an anti-allodynic effect on the mechanical and thermal threshold in all lineages; however, these effects were lower in the CHF and CLF lineages. Considering emotional evaluation, we observed an anxiolytic effect in CTL+CCI and CHF+CCI after CBD treatment and increased mobility in CLF+SHAM rats. These results suggest that the CBD mechanical anti-allodynic and emotional effects can depend on anxiety level.

Social buffering reduces fear expression in Wistar rats when tested in pairs, but not when retested alone

Social buffering is a phenomenon in which the stress response of an individual can be reduced by the presence of another individual. However, little is known about the effect of social buffering on aversive after memory extinction, especially when animals are tested alone afterwards. The aim of this study was to verify the social buffering effect in rats during the extinction session of the contextual fear conditioning model and the fear response when animals are tested alone in the following day. Animals were divided into subjects and associates, with the subjects undergoing the fear conditioning protocol and the associates paired with the subjects during the fear extinction session. Across five different experiments, we tested moderate and high intensity contextual fear conditioning protocols, as well four variations of pairs: (i) two conditioned subjects, (ii) a conditioned subject and a non-conditioned associate, (iii) a conditioned subject and an associate who observed the conditioning of the partner and (iv) two conditioned subjects, with one treated with diazepam. The social buffering effect was found efficient to reduce the fear memory expression during the fear extinction session. In the moderate intensity protocol, the reduction in freezing time occurred only in subjects accompanied by non-conditioned associates and observer associates. In the high intensity protocol, the social buffering effect occurred in subjects accompanied by either conditioned or non-conditioned associates, although the effect was more evident in the presence of non-conditioned subjects. Treatment of the conditioned associates with diazepam did not improve the social buffering effect. Moreover, social buffering effects were not correlated with self-grooming or prosocial behaviors, which indicates that the presence of another animal might decrease freezing by promotion of exploratory activity. Finally, the social buffering effect was not observed in the extinction test, either because the extinction was too effective in the moderate intensity protocol or because the extinction was equally ineffective in the high intensity protocol. Our results suggest that social buffering does not improve fear extinction consolidation.

On making (and turning adaptive to) maladaptive aversive memories in laboratory rodents

Fear conditioning and avoidance tasks usually elicit adaptive aversive memories. Traumatic memories are more intense, generalized, inflexible, and resistant to attenuation via extinction- and reconsolidation-based strategies. Inducing and assessing these dysfunctional, maladaptive features in the laboratory are crucial to interrogating posttraumatic stress disorder's neurobiology and exploring innovative treatments. Here we analyze over 350 studies addressing this question in adult rats and mice. There is a growing interest in modeling several qualitative and quantitative memory changes by exposing already stressed animals to freezing- and avoidance-related tests or using a relatively high aversive training magnitude. Other options combine aversive/fearful tasks with post-acquisition or post-retrieval administration of one or more drugs provoking neurochemical or epigenetic alterations reported in the trauma aftermath. It is potentially instructive to integrate these procedures and incorporate the measurement of autonomic and endocrine parameters. Factors to consider when defining the organismic and procedural variables, partially neglected aspects (sex-dependent differences and recent vs. remote data comparison) and suggestions for future research (identifying reliable individual risk and treatment-response predictors) are discussed.

Oral lipid-based formulations alter delivery of cannabidiol to different anatomical regions in the brain

Delivery to the brain is a challenging task due to its protection by the blood-brain barrier (BBB). Lipids and fatty acids are reported to affect the permeability of the BBB, although this has not been reported following oral administration. Cannabidiol (CBD) has high therapeutic potential in the brain, therefore, this work investigated CBD delivery to anatomical brain regions following oral administration in lipid-based and lipid-free vehicles. All formulations resulted in a short brain T_max (1 h) and brain-plasma ratios ≥ 3.5, with retention up to 18 h post administration. The highest CBD delivery was observed in the olfactory bulb and striatum, and the medulla pons and cerebellum the lowest. The lipid-free vehicle led to the highest levels of CBD in the whole brain. However, when each anatomical region was assessed individually, the long chain triglyceride-rich rapeseed oil formulation commonly showed optimal performance. The medium chain triglyceride-rich coconut oil formulation did not result in the highest CBD concentration in any brain region. Overall, differences in CBD delivery to the whole brain and various brain regions were observed following administration in different formulations, indicating that the oral formulation selection may be important for optimal delivery to specific regions of the brain.

Effects of delta-9 tetrahydrocannabinol on fear memory labilization and reconsolidation: A putative role of GluN2B-NMDA receptor within the dorsal hippocampus

Cannabis preparations could be an effective reconsolidation-based treatment for post-traumatic stress disorder. However, the effects of Δ⁹-tetrahydrocannabinol (THC) in fear memory labilization, a critical condition for retrieval-induced reconsolidation, are undetermined. We sought to investigate the effect of a conventional and an ultra-low dose of THC in memory labilization of adult male Wistar rats submitted to contextual fear conditioning. Pretreatment with THC 0.002, but not THC 0.3 mg/kg, i. p., before memory retrieval, did not change memory expression during the retrieval but impaired reconsolidation. No treatment changed freezing expression in an unpaired context. Before retrieval, THC 0.3, but not THC 0.002, decreased GluN2A-NMDA expression and the GluN2A/GluN2B ratio in the dorsal hippocampus (DH) 24 h later. No changes were observed immediately after retrieval. Pretreatment with THC 0.3 abolished the reconsolidation-impairing effect of anisomycin injected into the DH, suggesting an impairment in memory labilization. This effect was associated with an increased freezing expression in the unpaired context and was not observed with the THC ultra-low dose. The GluN2B-NMDA antagonism increased fear generalization in the anisomycin-treated group but restored its reconsolidation-impairing effect and reduced fear generalization when animals were pretreated with THC 0.3. GluN2A-NMDA antagonism or inhibition of the ubiquitin-proteasome system in the DH did not interfere with the effects of THC 0.3. Our findings indicate that THC causes a bidirectional effect on fear memory labilization that depends on hippocampal GluN2B-NMDA receptors' involvement in fear memory generalization.

Cannabidiol attenuates fear memory expression in female rats via hippocampal 5-HT1A but not CB1 or CB2 receptors

Growing evidence from male rodent and human studies suggests that cannabidiol (CBD) modulates the expression of aversive memories and anxiety-related responses. The limited data on whether and how CBD influences these aspects in females could have therapeutic implications given the increased susceptibility of women to anxiety- and stress-related disorders relative to men. Female studies are also essential to examine inherent aspects that potentially contribute to differences in responsiveness to CBD. Here we addressed these questions in adult female rats. Contextually fear-conditioned animals acutely treated with CBD (1.0-10 mg/kg) were tested 45 min later. In subsequent experiments, we investigated the estrous cycle effects and the contribution of dorsal hippocampus (DH) serotonin 1A (5-HT1A) and cannabinoid types 1 (CB1) and 2 (CB2) receptors to CBD-induced effects on memory retrieval/expression. The effects of pre-retrieval systemic or intra-DH CBD administration on subsequent fear extinction were also assessed. Lastly, we evaluated the open arms avoidance and stretched-attend postures in females exposed to the elevated plus-maze after systemic CBD treatment. CBD 3.0 and 10 mg/kg administered before conditioned context exposure reduced females' freezing. This action remained unchanged across the estrous cycle and involved DH 5-HT1A receptors activation. Pre-retrieval CBD impaired memory reconsolidation and lowered fear during early extinction. CBD applied directly to the DH was sufficient to reproduce the effects of systemic CBD treatment. CBD 3.0 and 10 mg/kg reduced anxiety-related responses scored in the elevated plus-maze. Our findings demonstrate that CBD attenuates the behavioral manifestation of learned fear and anxiety in female rats.

Effect of Cannabis on Memory Consolidation, Learning and Retrieval and Its Current Legal Status in India: A Review

Cannabis is one of the oldest crops grown, traditionally held religious attachments in various cultures for its medicinal use much before its introduction to Western medicine. Multiple preclinical and clinical investigations have explored the beneficial effects of cannabis in various neurocognitive and neurodegenerative diseases affecting the cognitive domains. Tetrahydrocannabinol (THC), the major psychoactive component, is responsible for cognition-related deficits, while cannabidiol (CBD), a non-psychoactive phytocannabinoid, has been shown to elicit neuroprotective activity. In the present integrative review, the authors focus on the effects of cannabis on the different cognitive domains, including learning, consolidation, and retrieval. The present study is the first attempt in which significant focus has been imparted on all three aspects of cognition, thus linking to its usage. Furthermore, the investigators have also depicted the current legal position of cannabis in India and the requirement for reforms.

The NLRP3 Inflammasome in Stress Response: Another Target for the Promiscuous Cannabidiol

Many psychiatric patients do not respond to conventional therapy. There is a vast effort to investigate possible mechanisms involved in treatment resistance, trying to provide better treatment options, and several data points toward a possible involvement of inflammatory mechanisms. Microglia, glial, and resident immune cells are involved in complex responses in the brain, orchestrating homeostatic functions, such as synaptic pruning and maintaining neuronal activity. In contrast, microglia play a major role in neuroinflammation, neurodegeneration, and cell death. Increasing evidence implicate microglia dysfunction in neuropsychiatric disorders. The mechanisms are still unclear, but one pathway in microglia has received increased attention in the last 8 years, i.e., the NLRP3 inflammasome pathway. Stress response and inflammation, including microglia activation, can be attenuated by Cannabidiol (CBD). CBD has antidepressant, anti-stress, antipsychotic, anti-inflammatory, and other properties. CBD effects are mediated by direct or indirect modulation of many receptors, enzymes, and other targets. This review will highlight some findings for neuroinflammation and microglia involvement in stress-related psychiatric disorders, particularly addressing the NLRP3 inflammasome pathway. Moreover, we will discuss evidence and mechanisms for CBD effects in psychiatric disorders and animal models and address its potential effects on stress response via neuroinflammation and NLRP3 inflammasome modulation.

Epigenomic and Other Evidence for Cannabis-Induced Aging Contextualized in a Synthetic Epidemiologic Overview of Cannabinoid-Related Teratogenesis and Cannabinoid-Related Carcinogenesis

BACKGROUND

Twelve separate streams of empirical data make a strong case for cannabis-induced accelerated aging including hormonal, mitochondriopathic, cardiovascular, hepatotoxic, immunological, genotoxic, epigenotoxic, disruption of chromosomal physiology, congenital anomalies, cancers including inheritable tumorigenesis, telomerase inhibition and elevated mortality.

METHODS

Results from a recently published longitudinal epigenomic screen were analyzed with regard to the results of recent large epidemiological studies of the causal impacts of cannabis. We also integrate theoretical syntheses with prior studies into these combined epigenomic and epidemiological results.

RESULTS

Cannabis dependence not only recapitulates many of the key features of aging, but is characterized by both age-defining and age-generating illnesses including immunomodulation, hepatic inflammation, many psychiatric syndromes with a neuroinflammatory basis, genotoxicity and epigenotoxicity. DNA breaks, chromosomal breakage-fusion-bridge morphologies and likely cycles, and altered intergenerational DNA methylation and disruption of both the histone and tubulin codes in the context of increased clinical congenital anomalies, cancers and heritable tumors imply widespread disruption of the genome and epigenome. Modern epigenomic clocks indicate that, in cannabis-dependent patients, cannabis advances cellular DNA methylation age by 25-30% at age 30 years. Data have implications not only for somatic but also stem cell and germ line tissues including post-fertilization zygotes. This effect is likely increases with the square of chronological age.

CONCLUSION

Recent epigenomic studies of cannabis exposure provide many explanations for the broad spectrum of cannabis-related teratogenicity and carcinogenicity and appear to account for many epidemiologically observed findings. Further research is indicated on the role of cannabinoids in the aging process both developmentally and longitudinally, from stem cell to germ cell to blastocystoids to embryoid bodies and beyond.

Cannabidiol impairs fear memory reconsolidation in female rats through dorsal hippocampus CB1 but not CB2 receptor interaction

Women present increased susceptibility to anxiety- and stress-related disorders compared to men. A potentially promising pharmacological-based strategy to regulate abnormal aversive memories disrupts their reconsolidation stage after reactivation and destabilization. Male rodent findings indicate that cannabidiol (CBD), a relatively safe and effective treatment for several mental health conditions, can impair the reconsolidation of aversive memories. However, whether and how CBD influences it in females is still unknown. The present study addressed this question in contextually fear-conditioned female rats. We report that systemically administered CBD impaired their reconsolidation, reducing freezing expression for over a week. This action was restricted to a time when the reconsolidation presumably lasted (< six hours post-retrieval) and depended on memory reactivation/destabilization. Moreover, the impairing effects of CBD on memory reconsolidation relied on the activation of cannabinoid type-1 but not type-2 receptors located in the CA1 subregion of the dorsal hippocampus. CBD applied directly to this brain area was sufficient to reproduce the effects of systemic CBD treatment. Contextual fear memories attenuated by CBD did not show reinstatement, an extinction-related feature. By demonstrating that destabilized fear memories are sensitive to CBD and how it hinders mechanisms in the DH CA1 that may restabilize them in female rats, the present findings concur that reconsolidation blockers are viable and could be effective in disrupting abnormally persistent and distressing aversive memories such as those related to posttraumatic stress disorder.

Use of Cannabidiol (CBD) oil in the treatment of PTSD: Study design and rationale for a placebo-controlled randomized clinical trial

BACKGROUND

The burden of illness for PTSD is staggering and confers significant interference in work, social functioning, as well as increased risk for other physical and mental health problems. Recently, there's been considerable attention paid to the potential therapeutic use of cannabidiol (CBD) products in the treatment of a variety of physical and mental health problems. The endocannabinoid system (ECS) is a logical therapeutic target for combating PTSD and other fear-based disorders given that cannabinoid receptors and other molecular mediators crucial for ECS signaling are richly expressed in a variety of brain regions that govern the regulation of learned fear and defensive behavior.

METHODS

This is an 8-week single-site Phase II randomized double-blind placebo-controlled fixed dose clinical trial. Participants recruited throughout the United States (N = 150) meeting DSM-5 criteria for posttraumatic stress disorder are randomly assigned to one of three treatment arms: (a) 300 mg CBD Isolate; (b) 300 mg CBD Broad Spectrum; and (c) Placebo oil. The primary outcome is PTSD symptom severity as indexed by the PTSD Checklist for DSM-5 (PCL-5) assessed at post treatment (Week 9) and follow-up (Week 13). Secondary outcomes including patient-rated depression, overall disability, anxiety, quality of life, and alcohol use are assessed weekly throughout the trial. Safety and CBD adherence are assessed daily throughout the trial.

CONCLUSION

This is the first placebo-controlled clinical trial investigating (a) CBD for the treatment of PTSD; and (b) the first study to test the relative efficacy of CBD Isolate vs CBD Broad Spectrum. Trial registration ClinicalTrials.gov registered (12/12/2019), trial identifier NCT04197102.

PROTOCOL VERSION

issued 08/04/2022, protocol amendment number #2019-05-0123.

The Efficacy of Psychedelic-Assisted Therapy in Managing Post-traumatic Stress Disorder (PTSD): A New Frontier?

Post-traumatic stress disorder (PTSD) is a significant public health concern for which existing therapies are only marginally effective. Indisputably, the primary line of treatment for PTSD is psychotherapy, according to current treatment guidelines. However, PTSD continues to be a chronic condition even after psychotherapy, with high psychiatric and medical illness rates. There is a dire need to search for new compounds and approaches for managing PTSD. The usage of psychedelic substances is a potential new method. This article reviews the efficacy of psychedelic-assisted therapy in treating PTSD and improving patient outcomes. It will examine current research on the topic and evaluate the benefits and drawbacks of different therapies. The current evidence for the use of four different types of psychedelics (3,4-methylenedioxymethamphetamine, ketamine, classical psychedelics, and cannabis) in the treatment of PTSD will be reviewed. It will also include an overview of the therapeutic justification, context of use, and level of evidence available for each drug. Several questions are formulated that could be studied in future research in order to gain a better understanding of the topic.

Evidence on the impairing effects of Ayahuasca on fear memory reconsolidation

RATIONALE

To uncover whether psychedelic drugs attenuate fear memory responses would advance the development of better psychedelic-based treatments for posttraumatic stress disorder (PTSD). Ayahuasca (AYA), a psychedelic brew containing indolamine N, N-dimethyltryptamine (DMT) and β-carbolines, facilitates fear extinction and improves neural plasticity. Upon retrieval, fear memory undergoes labilization and reconsolidation; however, the effects of AYA on this memory stabilization phase are unknown.

OBJECTIVES

We aimed to investigate the effects of AYA treatment on fear memory reconsolidation.

METHODS

Fear-conditioned Wistar rats received AYA (60, 120, or 240 mg/kg) or H₂O orally via gavage o.g. 20 min before, immediately, or 3 h after a short retrieval session. Analysis of AYA through liquid chromatography-tandem mass spectrometry was used to determine the content of DMT and β-carbolines in AYA.

RESULTS

AYA impaired fear memory reconsolidation when given 20 min before or 3 h after memory retrieval, with the dose of 60 mg/kg being effective at both moments. This dose of AYA was devoid of anxiolytic effect. Importantly, during retrieval, AYA did not change fear expression. The lack of retrieval abolished the reconsolidation impairing effect of AYA. The effects of AYA treatment 20 min before or 3 h after memory retrieval lasted at least 22 days, suggesting no spontaneous recovery of fear memory. Fear memory impairments induced by AYA treatment, at both moments, do not show reinstatement.

CONCLUSIONS

Our findings support the view that a low dose of AYA treatment impairs early and late stages of memory reconsolidation instead of facilitating fear extinction.

Effects of Cannabis on PTSD Recovery: Review of the Literature and Clinical Insights

Purpose of Review

Individuals with posttraumatic stress disorder (PTSD) may use cannabis to reduce symptoms yet are also at risk for developing problematic use. This review outlines theories, summarizes recent empirical studies, and discusses clinical implications of cannabis use and PTSD recovery.

Recent Findings

Although naturalistic studies and open trials find a relationship between cannabinoids and PTSD symptom reduction, methodological limitations preclude definitive conclusions. The only randomized controlled trial to date found cannabis had no greater effect on PTSD symptoms than placebo.

Summary

Rigorous studies of the long-term impact of cannabis use on PTSD recovery are needed. Clinicians and researchers must weigh the potential therapeutic effect against the costs and risks associated with long-term cannabis use. Clinicians should consider all available PTSD treatment options, along with client level factors such as the function of cannabis use, motivation to change use, and the potential impact of cannabis on treatment engagement when making clinical recommendations.

Cannabidiol Prevents Spontaneous Fear Recovery after Extinction and Ameliorates Stress-Induced Extinction Resistance

Cannabidiol, the main non-psychotropic constituent of cannabis, has potential as a treatment for anxiety-related disorders since it reduces learned fear expression and enhances fear extinction. The return of fear over time after successful extinction and stress-induced extinction resistance are potential barriers to the treatment of these disorders with extinction-based psychological therapy. In two experiments using rats subjected to auditory fear conditioning, we determined the effects of systemic cannabidiol treatment on (1) delayed extinction and later spontaneous fear recovery, and (2) extinction resistance caused by immediate extinction (the immediate extinction deficit (IED)). In Experiment 1, cannabidiol was given before delayed extinction occurring 24 h after conditioning, with extinction recall and spontaneous fear recovery tested drug-free 1 and 21 days after extinction, respectively. We found that cannabidiol had no effect on extinction recall but it prevented spontaneous fear recovery. In Experiment 2, the IED procedure was first validated, with immediate extinction occurring 30 min after conditioning. We confirmed that immediate extinction impaired extinction recall, compared to delayed extinction. Next, cannabidiol was given before immediate or no extinction, with extinction recall tested drug-free the next day. We found that cannabidiol rescued the IED, which did not involve effects on fear memory consolidation. In summary, cannabidiol prevented spontaneous fear recovery after delayed extinction and ameliorated extinction resistance caused by immediate extinction. Although the pharmacological mechanisms underlying these effects remain to be determined, our results add to evidence indicating that cannabidiol might prove useful as an adjunct for potentiating the psychological treatment of anxiety-related disorders.

The Cannabis Constituent Cannabigerol Does Not Disrupt Fear Memory Processes or Stress-Induced Anxiety in Mice

Introduction: Medicinal cannabis has proliferated around the world and there is increasing interest in the therapeutic potential of individual plant-derived cannabinoids (phytocannabinoids). Preclinical evidence suggests the phytocannabinoid cannabigerol (CBG) could be useful in treating brain disorders, including stress and anxiety-related disorders. In this study, we aimed to explore whether CBG disrupts various contextually conditioned fear memory processes and trauma-induced anxiety-related behavior in a mouse model of post-traumatic stress disorder (PTSD). Materials and Methods: All mice underwent contextual fear conditioning. CBG was administered between 1 and 60 mg/kg intraperitoneally (i.p.). We first assessed the effects of repeated CBG exposure on long-term fear memories. We also examined whether acute CBG affected various fear memory processes, namely expression, acquisition, consolidation, and reconsolidation of conditioned fear. Finally, the effect of acute CBG administration on stress-induced anxiety in the light/dark test was assessed. Results: Repeated CBG exposure did not affect long-term conditioned fear that was observed 24 days after the conditioning session. Moreover, acute CBG administration did not influence the acquisition, consolidation, reconsolidation, or expression of contextually conditioned fear. Acute CBG treatment also did not affect stress-induced anxiety-related behaviors in the light/dark test. Conclusions: CBG was ineffective in disrupting long-term fear memories, various conditioned fear memory processes, or stress-induced anxiety-related behavior in mice. These preclinical data suggest CBG may have limited scope in the treatment of PTSD and stress-related anxiety.

Modulation of Endocannabinoid System Components in Depression: Pre-Clinical and Clinical Evidence

Depression is characterized by continuous low mood and loss of interest or pleasure in enjoyable activities. First-line medications for mood disorders mostly target the monoaminergic system; however, many patients do not find relief with these medications, and those who do suffer from negative side effects and a discouragingly low rate of remission. Studies suggest that the endocannabinoid system (ECS) may be involved in the etiology of depression and that targeting the ECS has the potential to alleviate depression. ECS components (such as receptors, endocannabinoid ligands, and degrading enzymes) are key neuromodulators in motivation and cognition as well as in the regulation of stress and emotions. Studies in depressed patients and in animal models for depression have reported deficits in ECS components, which is motivating researchers to identify potential diagnostic and therapeutic biomarkers within the ECS. By understanding the effects of cannabinoids on ECS components in depression, we enhance our understanding of which brain targets they hit, what biological processes they alter, and eventually how to use this information to design better therapeutic options. In this article, we discuss the literature on the effects of cannabinoids on ECS components of specific depression-like behaviors and phenotypes in rodents and then describe the findings in depressed patients. A better understanding of the effects of cannabinoids on ECS components in depression may direct future research efforts to enhance diagnosis and treatment.

Effects of cannabidiol on symptoms induced by the recall of traumatic events in patients with posttraumatic stress disorder

Studies with cannabidiol (CBD) suggest that this compound has anxiolytic properties and may mediate the reconsolidation and extinction of aversive memories. The objective of this study was to test whether the administration of CBD 300 mg before the recall of traumatic events attenuated symptoms usually induced by recall in subjects diagnosed with posttraumatic stress disorder (PTSD) and if its potential effects interfere with the reconsolidation of aversive memories. The double-blind trial included 33 participants of both sexes, aged between 18 and 60 years, diagnosed with PTSD according to the SCID-5 and randomly allocated to two groups treated with CBD (n = 17) and placebo (n = 16). In the first experimental section, participants were matched by sex, age, body mass index (BMI), and PTSD symptoms as assessed with the Posttraumatic Stress Disorder Checklist (PCL-5). On the same day, participants prepared the behavior test, recording accounts of their traumas in digital audio for a minute and a half and then imagining the trauma for 30 s. After 7 days, participants received CBD (300 mg) or placebo and performed the behavioral test, listening to the trauma account and imagining themselves in that situation. Before and after the behavioral test, subjective changes in mood and anxiety were recorded (Visual and Analogical Mood Scale - VAMS and STAI-state), along with physiological correlates of anxiety blood pressure (BP), heart rate (HR), and salivary cortisol (SC). Seven days later, participants underwent the same procedures as the previous session, but without the pharmacological intervention, to assess the effect on reconsolidation of traumatic memories. We found that CBD significantly attenuated the increase in the VAMS scale cognitive impairment factor scores, under the CBD's effect, with this effect remaining 1 week after drug administration. No significant differences between the effects of CBD and placebo on anxiety, alertness, and discomfort induced by the recall of the traumatic event during the pharmacological intervention and in the subsequent week, in the absence of it. There were no significant differences between the CBD and placebo groups regarding physiological data (BP, HR, and SC). The attenuation of cognitive impairments during trauma recall under the effect of CBD may have interfered with the reconsolidation of traumatic memories concerning its association with cognitive impairments.

Geotemporospatial and causal inferential epidemiological overview and survey of USA cannabis, cannabidiol and cannabinoid genotoxicity expressed in cancer incidence 2003-2017: part 1 - continuous bivariate analysis

BACKGROUND

The genotoxic and cancerogenic impacts of population-wide cannabinoid exposure remains an open but highly salient question. The present report examines these issues from a continuous bivariate perspective with subsequent reports continuing categorical and detailed analyses.

METHODS

Age-standardized state census incidence of 28 cancer types (including "All (non-skin) Cancer") was sourced using SEER*Stat software from Centres for Disease Control and National Cancer Institute across US states 2001-2017. It was joined with drug exposure data from the nationally representative National Survey of Drug Use and Health conducted annually by the Substance Abuse and Mental Health Services Administration 2003-2017, response rate 74.1%. Cannabinoid data was from Federal seizure data. Income and ethnicity data sourced from the US Census Bureau. Data was processed in R.

RESULTS

Nineteen thousand eight hundred seventy-seven age-standardized cancer rates were returned. Based on these rates and state populations this equated to 51,623,922 cancer cases over an aggregated population 2003-2017 of 124,896,418,350. Regression lines were charted for cancer-substance exposures for cigarettes, alcohol use disorder (AUD), cannabis, THC, cannabidiol, cannabichromene, cannabinol and cannabigerol. In this substance series positive trends were found for 14, 9, 6, 9, 12, 6, 9 and 7 cancers; with largest minimum E-Values (mEV) of 1.76 × 109, 4.67 × 108, 2.74 × 104, 4.72, 2.34 × 1018, 2.74 × 1017, 1.90 × 107, 5.05 × 109; and total sum of exponents of mEV of 34, 32, 13, 0, 103, 58, 25, 31 indicating that cannabidiol followed by cannabichromene are the most strongly implicated in environmental carcinogenesis. Breast cancer was associated with tobacco and all cannabinoids (from mEV = 3.53 × 109); "All Cancer" (non-skin) linked with cannabidiol (mEV = 1.43 × 1011); pediatric AML linked with cannabis (mEV = 19.61); testicular cancer linked with THC (mEV = 1.33). Cancers demonstrating elevated mEV in association with THC were: thyroid, liver, pancreas, AML, breast, oropharynx, CML, testis and kidney. Cancers demonstrating elevated mEV in relation to cannabidiol: prostate, bladder, ovary, all cancers, colorectum, Hodgkins, brain, Non-Hodgkins lymphoma, esophagus, breast and stomach.

CONCLUSION

Data suggest that cannabinoids including THC and cannabidiol are important community carcinogens exceeding the effects of tobacco or alcohol. Testicular, (prostatic) and ovarian tumours indicate mutagenic corruption of the germline in both sexes; pediatric tumourigenesis confirms transgenerational oncogenesis; quantitative criteria implying causality are fulfilled.

Geospatiotemporal and causal inference study of cannabis and other drugs as risk factors for female breast cancer USA 2003-2017

Breast cancer (BC) is the commonest human cancer and its incidence (BC incidence, BCI) is rising worldwide. Whilst both tobacco and alcohol have been linked to BCI genotoxic cannabinoids have not been investigated. Age-adjusted state-based BCI 2003-2017 was taken from the Surveillance Epidemiology and End Results database of the Centers for Disease Control. Drug use from the National Survey of Drug Use and Health, response rate 74.1%. Median age, median household income and ethnicity were from US census. Inverse probability weighted (ipw) multivariable regression conducted in R. In bivariate analysis BCI was shown to be significantly linked with rising cannabis exposure {β-est. = 3.93 [95% confidence interval 2.99, 4.87], P = 1.10 × 10-15}. At 8 years lag cigarettes:cannabis [β-est. = 2660 (2150.4, 3169.3), P = 4.60 × 10-22] and cannabis:alcoholism [β-est. = 7010 (5461.6, 8558.4), P = 1.80 × 10-17] were significant in ipw-panel regression. Terms including cannabidiol [CBD; β-est. = 16.16 (0.39, 31.93), P = 0.446] and cannabigerol [CBG; β-est. = 6.23 (2.06, 10.39), P = 0.0034] were significant in spatiotemporal models lagged 1:2 years, respectively. Cannabis-liberal paradigms had higher BCI [67.50 ± 0.26 v. 65.19 ± 0.21/100 000 (mean ± SEM), P = 1.87 × 10-11; β-est. = 2.31 (1.65, 2.96), P = 9.09 × 10-12]. 55/58 expected values >1.25 and 13/58 >100. Abortion was independently and causally significant in space-time models. Data show that exposure to cannabis and the cannabinoids Δ9-tetrahydrocannabinol, CBD, CBG and alcoholism fulfil quantitative causal criteria for BCI across space and time. Findings are robust to adjustment for age and several known sociodemographic, socio-economic and hormonal risk factors and establish cannabinoids as an additional risk factor class for breast carcinogenesis. BCI is higher under cannabis-liberal legal paradigms.

Medial prefrontal cortex mechanisms of cannabidiol-induced aversive memory reconsolidation impairments

Growing evidence indicates that cannabidiol (CBD), a substance present in the Cannabis sativa plant, has potential therapeutic value to regulate abnormal emotional memories associated with post-traumatic stress and drug use disorders. CBD can attenuate their valence after retrieval (i.e., during reconsolidation) or potentiate their suppression by extinction. Pharmacological research has now focused on elucidating how it acts. Systemic antagonism of cannabinoid type-1 (CB1) receptors has often prevented the abovementioned effects of CBD. However, it is unknown in which brain regions CBD stimulates CB1 receptors and how it interferes with local activity-related plasticity to produce these effects. The present study addressed these questions considering the reconsolidation of contextual fear memories in rats. We focused on the medial prefrontal cortex (mPFC), which comprises the anterior cingulate (AC), prelimbic (PL), and infralimbic (IL) subregions, as local activity or plasticity has been associated with the process to-be-investigated. Animals that received post-retrieval systemic CBD treatment presented relatively fewer cells expressing Zif268/Egr1 protein, a proxy for synaptic plasticity related to reconsolidation, in the AC and PL. At the same time, there were no significant differences in the IL. Pretreatment with the CB1 receptor antagonist/inverse agonist AM251 into the AC, PL, or IL prevented the impairing effects of systemic CBD treatment on reconsolidation. CBD also caused reconsolidation impairments when injected directly into the AC or PL but not the IL. Together, these findings show complementary mechanisms through which CBD may hinder the reconsolidation of destabilized aversive memories along the dorsoventral axis of the mPFC.

Hippocampal Cb2 receptors: an untold story

The field of cannabinoid research has been receiving ever-growing interest. Ongoing debates worldwide about the legislation of medical cannabis further motivates research into cannabinoid function within the central nervous system (CNS). To date, two well-characterized cannabinoid receptors exist. While most research has investigated Cb₁ receptors (Cb₁Rs), Cb₂ receptors (Cb₂Rs) in the brain have started to attract considerable interest in recent years. With indisputable evidence showing the wide-distribution of Cb₂Rs in the brain of different species, they are no longer considered just peripheral receptors. However, in contrast to Cb₁Rs, the functionality of central Cb₂Rs remains largely unexplored. Here we review recent studies on hippocampal Cb₂Rs. While conflicting results about their function have been reported, we have made significant progress in understanding the involvement of Cb₂Rs in modulating cellular properties and network excitability. Moreover, Cb₂Rs have been shown to be expressed in different subregions of the hippocampus, challenging our prior understanding of the endocannabinoid system. Although more insight into their functional roles is necessary, we propose that targeting hippocampal Cb₂Rs may offer novel therapies for diseases related to memory and adult neurogenesis deficits.

Interactions of Noradrenergic, Glucocorticoid and Endocannabinoid Systems Intensify and Generalize Fear Memory Traces

Systemic administration of drugs that activate the noradrenergic or glucocorticoid system potentiates aversive memory consolidation and reconsolidation. The opposite happens with the stimulation of endocannabinoid signaling under certain conditions. An unbalance of these interacting neurotransmitters can lead to the formation and maintenance of traumatic memories, whose strength and specificity attributes are often maladaptive. Here we aimed to investigate whether originally low-intensity and precise contextual fear memories would turn similar to traumatic ones in rats systemically administered with adrenaline, corticosterone, and/or the cannabinoid type-1 receptor antagonist/inverse agonist AM251 during consolidation or reconsolidation. The high dose of each pharmacological agent evaluated significantly increased freezing times at test in the conditioning context one and nine days later when given alone post-acquisition or post-retrieval. Their respective low dose produced no relative changes when given separately, but co-treatment of adrenaline with corticosterone or AM251 and the three drugs combined, but not corticosterone with AM251, produced results equivalent to those mentioned initially. Neither the high nor the low dose of adrenaline, corticosterone, or AM251 altered freezing times at test in a novel, neutral context two and ten days later. In contrast, animals receiving the association of their low dose exhibited significantly higher freezing times than controls. Together, the results indicate that newly acquired and destabilized threat memory traces become more intense and generalized after a combined interference acting synergistically and mimicking that reported in patients presenting stress-related psychiatric conditions.

Clinical Outcome Data of First Cohort of Chronic Pain Patients Treated With Cannabis-Based Sublingual Oils in the United Kingdom: Analysis From the UK Medical Cannabis Registry

Cannabis-based medicinal products (CBMPs) are an emerging therapeutic option in the management of primary chronic pain, using the role of the endocannabinoid system in modulating central and peripheral pain processes. Despite promising preclinical data, there is a paucity of high-quality evidence to support the use of CBMPs for chronic pain. This study aimed to investigate the health-related quality-of-life outcomes of patients with chronic pain who were prescribed CBMP oil preparations (Adven, Curaleaf International, Guernsey, UK). This study is a case series of patients from the UK Medical Cannabis Registry, who were treated with CBMP oils for an indication of chronic pain. The primary outcomes were the changes in Brief Pain Inventory short form, Short-Form McGill Pain Questionnaire-2, Visual Analog Scale Pain, General Anxiety Disorder-7, Sleep Quality Scale, and EQ-5D-5L, at 1, 3, and 6 months. One hundred ten patients were included. Significant improvements in Sleep Quality Scale, EQ-5D-5L pain and discomfort subscale, and Brief Pain Inventory Interference Subscale (P < .05) at 1, 3, and 6 months were demonstrated. There were no notable differences between cannabis-naïve and previous cannabis users in quality-of-life outcomes. The adverse event incidence was 30.0%, with most (n = 58; 92.1%) adverse events being mild or moderate in intensity. Treatment of chronic pain with Adven CBMP oils was associated with an improvement in pain-specific outcomes, health-related quality of life, and self-reported sleep quality. Relative safety was demonstrated over medium-term prescribed use. While these findings must be treated with caution considering the limitations of study design, they can inform future clinical trials.

Cannabidiol has a unique effect on global brain activity: a pharmacological, functional MRI study in awake mice

Background

The phytocannabinoid cannabidiol (CBD) exhibits anxiolytic activity and has been promoted as a potential treatment for post-traumatic stress disorders. How does CBD interact with the brain to alter behavior? We hypothesized that CBD would produce a dose-dependent reduction in brain activity and functional coupling in neural circuitry associated with fear and defense.

Methods

During the scanning session awake mice were given vehicle or CBD (3, 10, or 30 mg/kg I.P.) and imaged for 10 min post treatment. Mice were also treated with the 10 mg/kg dose of CBD and imaged 1 h later for resting state BOLD functional connectivity (rsFC). Imaging data were registered to a 3D MRI mouse atlas providing site-specific information on 138 different brain areas. Blood samples were collected for CBD measurements.

Results

CBD produced a dose-dependent polarization of activation along the rostral-caudal axis of the brain. The olfactory bulb and prefrontal cortex showed an increase in positive BOLD whereas the brainstem and cerebellum showed a decrease in BOLD signal. This negative BOLD affected many areas connected to the ascending reticular activating system (ARAS). The ARAS was decoupled to much of the brain but was hyperconnected to the olfactory system and prefrontal cortex.

Conclusion

The CBD-induced decrease in ARAS activity is consistent with an emerging literature suggesting that CBD reduces autonomic arousal under conditions of emotional and physical stress.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-021-02891-6.

Glial Cells and Their Contribution to the Mechanisms of Action of Cannabidiol in Neuropsychiatric Disorders

Cannabidiol (CBD) is a phytocannabinoid with a broad-range of therapeutic potential in several conditions, including neurological (epilepsy, neurodegenerative diseases, traumatic and ischemic brain injuries) and psychiatric disorders (schizophrenia, addiction, major depressive disorder, and anxiety). The pharmacological mechanisms responsible for these effects are still unclear, and more than 60 potential molecular targets have been described. Regarding neuropsychiatric disorders, most studies investigating these mechanisms have focused on neuronal cells. However, glial cells (astrocytes, oligodendrocytes, microglia) also play a crucial role in keeping the homeostasis of the central nervous system. Changes in glial functions have been associated with neuropathological conditions, including those for which CBD is proposed to be useful. Mostly in vitro studies have indicated that CBD modulate the activation of proinflammatory pathways, energy metabolism, calcium homeostasis, and the proliferative rate of glial cells. Likewise, some of the molecular targets proposed for CBD actions are f expressed in glial cells, including pharmacological receptors such as CB1, CB2, PPAR-γ, and 5-HT1A. In the present review, we discuss the currently available evidence suggesting that part of the CBD effects are mediated by interference with glial cell function. We also propose additional studies that need to be performed to unveil the contribution of glial cells to CBD effects in neuropsychiatric disorders.

Cannabidiol: A Potential New Alternative for the Treatment of Anxiety, Depression, and Psychotic Disorders

The potential therapeutic use of some Cannabis sativa plant compounds has been attracting great interest, especially for managing neuropsychiatric disorders due to the relative lack of efficacy of the current treatments. Numerous studies have been carried out using the main phytocannabinoids, tetrahydrocannabinol (THC) and cannabidiol (CBD). CBD displays an interesting pharmacological profile without the potential for becoming a drug of abuse, unlike THC. In this review, we focused on the anxiolytic, antidepressant, and antipsychotic effects of CBD found in animal and human studies. In rodents, results suggest that the effects of CBD depend on the dose, the strain, the administration time course (acute vs. chronic), and the route of administration. In addition, certain key targets have been related with these CBD pharmacological actions, including cannabinoid receptors (CB₁r and CB₂r), 5-HT_1A receptor and neurogenesis factors. Preliminary clinical trials also support the efficacy of CBD as an anxiolytic, antipsychotic, and antidepressant, and more importantly, a positive risk-benefit profile. These promising results support the development of large-scale studies to further evaluate CBD as a potential new drug for the treatment of these psychiatric disorders.

Emotional Impairments and Neuroinflammation are Induced in Male Mice Invulnerable to Repeated Social Defeat Stress

Prolonged stress triggers neuroinflammation, which plays a significant role in the development of depression; however, stressed people do not always suffer from depression because of individual differences in stress vulnerability. Negative cognitive bias (NCB) toward pessimistic judgment often underlies depressive episodes. However, a relationship between stress vulnerability, neuroinflammation, and NCB remains elusive. In addition, an animal model with all the traits would be a powerful tool for studying the etiology of depression and its therapeutic approaches. Accordingly, this study evaluated the effect of stress vulnerability on neuroinflammation and depression-related behaviors, including NCB in males, using a modified version of repeated social defeat stress (mRSDS) paradigm, a validated animal model of psychosocial stress. Exposure to mRSDS, consisting of 5 min of social defeat by unfamiliar CD-1 aggressor mice for five consecutive days, caused NCB, which co-occurred with depressive- and anxiety-like behaviors, and neuroinflammation in male BALB/c mice. Treatment with minocycline, an antibiotic with anti-inflammatory property, blocked mRSDS-induced depressive-like behaviors and neuroinflammation, but not NCB, indicating the limited effect of an anti-inflammatory intervention. In addition, marked differences were found in neuroinflammatory profiles and hippocampal gene expression patterns between resilient and unstressed mice, as well as between susceptible and resilient mice. Therefore, mice resilient to mRSDS are indeed not intact. Our findings provide insights into the unique features of the mRSDS model in male BALB/c mice, which could be used to investigate the etiological mechanisms underlying depression as well as bridge the gap in the relationship between stress vulnerability, neuroinflammation, and NCB in males.

The effects of acute cannabidiol on cerebral blood flow and its relationship to memory: An arterial spin labelling magnetic resonance imaging study

BACKGROUND

Cannabidiol (CBD) is being investigated as a potential treatment for several medical indications, many of which are characterised by altered memory processing. However, the mechanisms underlying these effects are unclear.

AIMS

Our primary aim was to investigate how CBD influences cerebral blood flow (CBF) in regions involved in memory processing. Our secondary aim was to determine if the effects of CBD on CBF were associated with differences in working and episodic memory task performance.

METHODS

We used a randomised, crossover, double-blind design in which 15 healthy participants were administered 600 mg oral CBD or placebo on separate days. We measured regional CBF at rest using arterial spin labelling 3 h after drug ingestion. We assessed working memory with the digit span (forward, backward) and n-back (0-back, 1-back, 2-back) tasks, and we used a prose recall task (immediate and delayed) to assess episodic memory.

RESULTS

CBD increased CBF in the hippocampus (mean (95% confidence intervals) = 15.00 (5.78-24.21) mL/100 g/min, t₁₄ = 3.489, Cohen's d = 0.75, p = 0.004). There were no differences in memory task performance, but there was a significant correlation whereby greater CBD-induced increases in orbitofrontal CBF were associated with reduced reaction time on the 2-back working memory task ( r= -0.73, p = 0.005).

CONCLUSIONS

These findings suggest that CBD increases CBF to key regions involved in memory processing, particularly the hippocampus. These results identify potential mechanisms of CBD for a range of conditions associated with altered memory processing, including Alzheimer's disease, schizophrenia, post-traumatic stress disorder and cannabis-use disorders.

Reviewing the Potential of Psychedelics for the Treatment of PTSD

There are few medications with demonstrated efficacy for the treatment of posttraumatic stress disorder (PTSD). Treatment guidelines have unequivocally designated psychotherapy as a first line treatment for PTSD. Yet, even after psychotherapy, PTSD often remains a chronic illness, with high rates of psychiatric and medical comorbidity. Meanwhile, the search for and development of drugs with new mechanisms of action has stalled. Therefore, there is an urgent need to explore not just novel compounds but novel approaches for the treatment of PTSD. A promising new approach involves the use of psychedelic drugs. Within the past few years, 2 psychedelics have received breakthrough designations for psychiatric indications from the US Food and Drug Administration, and several psychedelics are currently being investigated for the treatment of PTSD. This review discusses 4 types of compounds: 3,4-methylenedioxymethamphetamine, ketamine, classical psychedelics (e.g., psilocybin and lysergic acid diethylamide), and cannabinoids. We describe the therapeutic rationale, the setting in which they are being administered, and their current state of evidence in the treatment of PTSD. Each compound provides unique qualities for the treatment of PTSD, from their use to rapidly target symptoms to their use as adjuncts to facilitate psychotherapeutic treatments. Several questions are formulated that outline an agenda for future research.

Barriers to the wider adoption of medicinal Cannabis

The use of Cannabis-based preparations for medicinal use has waxed and waned in the multi-millennial history of human co-existence with the plant and its cultivation. Recorded use of preparations from Cannabis is effectively as old as recorded history with examples from China, India and Ancient Egypt. Prohibition and restriction of availability allowed a number of alternatives to take the place of Cannabis preparations. However, there has been a worldwide resurgence in medicinal Cannabis advocacy from the public. Media interest has been piqued by particular evocative cases. Altogether, therefore, there is pressure on healthcare professionals to prescribe and dispense Cannabis-based preparations. This review enunciates some of the barriers which are slowing the wider adoption of medicinal Cannabis.

Persistence of the extinction of fear memory requires late-phase cAMP/PKA signaling in the infralimbic cortex

Fear extinction is a form of new learning that inhibits expression of the original fear memory without erasing the conditioned stimulus-unconditioned stimulus association. Much is known about the mechanisms that underlie the acquisition of extinction, but the way in which fear extinction is maintained has been scarcely explored. Evidence suggests that protein kinase A (PKA) in the frontal cortex might be related to the persistence of extinction. Phosphodiesterase-4 (PDE4) specifically hydrolyzes cyclic adenosine monophosphate (cAMP). The present study evaluated the effect of the selective PDE4 inhibitor roflumilast (ROF; 0.01, 0.03, and 0.1 mg/kg given i.p.) on acquisition and consolidation of the extinction of fear memory in male Wistar rats in a contextual fear conditioning paradigm. When administered before acquisition, 0.1 mg/kg ROF disrupted short-term (1 day) extinction recall. In contrast, 0.03 mg/kg ROF administration in the late consolidation phase (3 h after extinction learning) but not in the early phase immediately after learning improved long-term extinction recall at 11 days, suggesting potentiation of the persistence of extinction. This effect of ROF requires the first (day 1) exposure to the context. A similar effect was observed when 9 ng ROF or 30 µM 8-bromoadenosine 3',5'-cAMP (PKA activator) was directly infused in the infralimbic cortex (IL), a brain region necessary for memory extinction. The PKA activity-dependent ROF-induced effect in the IL was correlated with an increase in its brain-derived neurotrophic factor (BDNF) protein expression, while blockade of PKA with 10 µM H89 in the IL abolished the ROF-induced increase in BDNF expression and prevented the effect of ROF on extinction recall. These effects were not associated with changes in anxiety-like behavior or general exploratory behavior. Altogether, these findings suggest that cAMP-PKA activity in the IL during the late consolidation phase after extinction learning underlies the persistence of extinction.