Localization of the CB1 cannabinoid receptor in the rat brain. An immunohistochemical study

Laminar Distribution of Cannabinoid Receptor 1 in the Prefrontal Cortex of Nonhuman Primates

Cannabis is an annual herb of the genus Cannabis, with a history of medical use going back thousands of years. However, its abuse causes many side-effects, including confusion of consciousness, alienation, and mental disorders such as schizophrenia and depression. Research conducted on rodents suggests that there are two types of cannabinoid receptors-cannabinoid receptor 1 (CB1R) and cannabinoid receptor 2 (CB2R). CB1R is found mostly in the central nervous system, particularly in the prefrontal cortex (PFC), and alterations in its expression in the PFC have been strongly linked to mental disorders. Within the layers of the PFC, Brodmann area 46 is associated with the processing of complex cognitive information. However, it remains unclear whether CB1R is expressed in the PFC 46 area of non-human primate. In this work, we applied western blotting along with immunofluorescent histochemical staining to investigate the distribution pattern of CB1R in the PFC of nonhuman primate, Our findings reveal that CB1R is highly expressed in the monkey PFC, especially in area 46. Furthermore, CB1R exhibits a layered distribution pattern within area 46 of the PFC, with the inner granular layer displaying the highest expression levels. Additionally, CB1R+PV+ cells are widely distributed in lay II-VI of area 46, with layer IV showing notable prevalence. In conclusion, CB1R is distributed in the PV interneurons in area 46 of the prefrontal cortex, particularly in layer IV, suggesting that cannabis may modulate PFC activities via regulating interneuron in the PFC. And cannabis-induced side effects may be caused by abnormal expression of CB1R.

Paradoxical kinesia may no longer be a paradox waiting for 100 years to be unraveled

Parkinson's disease (PD) is a progressive neurodegenerative disorder mainly characterized by bradykinesia and akinesia. Interestingly, these motor disabilities can depend on the patient emotional state. Disabled PD patients remain able to produce normal motor responses in the context of urgent or externally driven situations or even when exposed to appetitive cues such as music. To describe this phenomenon Souques coined the term "paradoxical kinesia" a century ago. Since then, the mechanisms underlying paradoxical kinesia are still unknown due to a paucity of valid animal models that replicate this phenomenon. To overcome this limitation, we established two animal models of paradoxical kinesia. Using these models, we investigated the neural mechanisms of paradoxical kinesia, with the results pointing to the inferior colliculus (IC) as a key structure. Intracollicular electrical deep brain stimulation, glutamatergic and GABAergic mechanisms may be involved in the elaboration of paradoxical kinesia. Since paradoxical kinesia might work by activation of some alternative pathway bypassing basal ganglia, we suggest the IC as a candidate to be part of this pathway.

Neuroinflammation in the Central Nervous System: Exploring the Evolving Influence of Endocannabinoid System

Neuroinflammation is a complex biological process that typically originates as a protective response in the brain. This inflammatory process is triggered by the release of pro-inflammatory substances like cytokines, prostaglandins, and reactive oxygen and nitrogen species from stimulated endothelial and glial cells, including those with pro-inflammatory functions, in the outer regions. While neuronal inflammation is common in various central nervous system disorders, the specific inflammatory pathways linked with different immune-mediated cell types and the various factors influencing the blood-brain barrier significantly contribute to disease-specific characteristics. The endocannabinoid system consists of cannabinoid receptors, endogenous cannabinoids, and enzymes responsible for synthesizing and metabolizing endocannabinoids. The primary cannabinoid receptor is CB1, predominantly found in specific brain regions such as the brainstem, cerebellum, hippocampus, and cortex. The presence of CB2 receptors in certain brain components, like cultured cerebellar granular cells, Purkinje fibers, and microglia, as well as in the areas like the cerebral cortex, hippocampus, and cerebellum is also evidenced by immunoblotting assays, radioligand binding, and autoradiography studies. Both CB1 and CB2 cannabinoid receptors exhibit noteworthy physiological responses and possess diverse neuromodulatory capabilities. This review primarily aims to outline the distribution of CB1 and CB2 receptors across different brain regions and explore their potential roles in regulating neuroinflammatory processes.

Synthesis and Preclinical Evaluation of Fluorinated 5-Azaindoles as CB2 PET Radioligands

Several classes of cannabinoid receptor type 2 radioligands have been evaluated for imaging of neuroinflammation, with successful clinical translation yet to take place. Here we describe the synthesis of fluorinated 5-azaindoles and pharmacological characterization and in vivo evaluation of 18F-radiolabeled analogues. [18F]2 (hCB2 Ki = 96.5 nM) and [18F]9 (hCB2 Ki = 7.7 nM) were prepared using Cu-mediated 18F-fluorination with non-decay-corrected radiochemical yields of 15 ± 6% and 18 ± 2% over 85 and 80 min, respectively, with high radiochemical purities (>97%) and molar activities (140-416 GBq/μmol). In PET imaging studies in rats, both [18F]2 and [18F]9 demonstrated specific binding in CB2-rich spleen after pretreatment with CB2-specific GW405833. Moreover, [18F]9 exhibited higher brain uptake at later time points in a murine model of neuroinflammation compared with a healthy control group. The results suggest further evaluation of azaindole based CB2 radioligands is warranted in other neuroinflammation models.

Cannabinoids Reduce Melanoma Cell Viability and Do Not Interfere with Commonly Used Targeted Therapy in Metastatic Melanoma In Vivo and In Vitro

Background: Cannabinoids are mainly used for recreational purposes, but also made their way into oncology, since these substances can be taken to increase appetite in tumour cachexia. Since there are some hints in the literature that cannabinoids might have some anti-cancerous effects, the aim of this study was to study if and how cannabinoids mediate pro-apoptotic effects in metastatic melanoma in vivo and in vitro and its value besides conventional targeted therapy in vivo. Methods: Several melanoma cell lines were treated with different concentrations of cannabinoids, and anti-cancerous efficacy was assessed by proliferation and apoptosis assays. Subsequent pathway analysis was performed using apoptosis, proliferation, flow cytometry and confocal microscopy data. The efficacy of cannabinoids in combination with trametinib was studied in NSG mice in vivo. Results: Cannabinoids reduced cell viability in multiple melanoma cell lines in a dose-dependent way. The effect was mediated by CB1, TRPV1 and PPARα receptors, whereby pharmacological blockade of all three receptors protected from cannabinoid-induced apoptosis. Cannabinoids initiated apoptosis by mitochondrial cytochrome c release with consecutive activation of different caspases. Essentially, cannabinoids significantly decreased tumour growth in vivo and were as potent as the MEK inhibitor trametinib. Conclusions: We could demonstrate that cannabinoids reduce cell viability in several melanoma cell lines, initiate apoptosis via the intrinsic apoptotic pathway by cytochrome c release and caspase activation and do not interfere with commonly used targeted therapy.

Astroglial CB1 receptors, energy metabolism, and gliotransmission: an integrated signaling system?

Astrocytes are key players in brain homeostasis and function. During the last years, several studies have cemented this notion by showing that these cells respond to neuronal signals and, via the release of molecules that modulate and support synaptic activity (gliotransmission) participates in the functions of the so-called tripartite synapse. Thus, besides their established control of brain metabolism, astrocytes can also actively control synaptic activity and behavior. Among the signaling pathways that shape the functions of astrocyte, the cannabinoid type-1 (CB1) receptor is emerging as a critical player in the control of both gliotransmission and the metabolic cooperation between astrocytes and neurons. In the present short review, we describe known and newly discovered properties of the astroglial CB1 receptors and their role in modulating brain function and behavior. Based on this evidence, we finally discuss how the functions and mode of actions of astrocyte CB1 receptors might represent a clear example of the inextricable relationship between energy metabolism and gliotransmission. These tight interactions will need to be taken into account for future research in astrocyte functions and call for a reinforcement of the theoretical and experimental bridges between studies on metabolic and synaptic functions of astrocytes.

Endocannabinoid 2-Arachidonoylglycerol Levels in the Anterior Cingulate Cortex, Caudate Putamen, Nucleus Accumbens, and Piriform Cortex Were Upregulated by Chronic Restraint Stress

Endocannabinoid 2-arachidonoylglycerol (2-AG) has been implicated in habituation to stress, and its augmentation reduces stress-induced anxiety-like behavior. Chronic restraint stress (CRS) changes the 2-AG levels in some gross brain areas, such as the forebrain. However, the detailed spatial distribution of 2-AG and its changes by CRS in stress processing-related anatomical structures such as the anterior cingulate cortex (ACC), caudate putamen (CP), nucleus accumbens (NAc), and piriform cortex (PIR) are still unclear. In this study, mice were restrained for 30 min in a 50 mL-centrifuge tube for eight consecutive days, followed by imaging of the coronal brain sections of control and stressed mice using desorption electrospray ionization mass spectrometry imaging (DESI-MSI). The results showed that from the forebrain to the cerebellum, 2-AG levels were highest in the hypothalamus and lowest in the hippocampal region. 2-AG levels were significantly (p < 0.05) upregulated and 2-AG precursors levels were significantly (p < 0.05) downregulated in the ACC, CP, NAc, and PIR of stressed mice compared with control mice. This study provided direct evidence of 2-AG expression and changes, suggesting that 2-AG levels are increased in the ACC CP, NAc, and PIR when individuals are under chronic stress.

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.

Effects of Prenatal Cannabinoids Exposure upon Placenta and Development of Respiratory Neural Circuits

Cannabis use has risen dangerously during pregnancy in the face of incipient therapeutic use and a growing perception of safety. The main psychoactive compound of the Cannabis sativa plant is the phytocannabinoid delta-9-tetrahydrocannabinol (A-9 THC), and its status as a teratogen is controversial. THC and its endogenous analogues, anandamide (AEA) and 2-AG, exert their actions through specific receptors (eCBr) that activate intracellular signaling pathways. CB1r and CB2r, also called classic cannabinoid receptors, together with their endogenous ligands and the enzymes that synthesize and degrade them, constitute the endocannabinoid system. This system is distributed ubiquitously in various central and peripheral tissues. Although the endocannabinoid system's most studied role is controlling the release of neurotransmitters in the central nervous system, the study of long-term exposure to cannabinoids on fetal development is not well known and is vital for understanding environmental or pathological embryo-fetal or postnatal conditions. Prenatal exposure to cannabinoids in animal models has induced changes in placental and embryo-fetal organs. Particularly, cannabinoids could influence both neural and nonneural tissues and induce embryo-fetal pathological conditions in critical processes such as neural respiratory control. This review aims at the acute and chronic effects of prenatal exposure to cannabinoids on placental function and the embryo-fetal neurodevelopment of the respiratory pattern. The information provided here will serve as a theoretical framework to critically evaluate the teratogen effects of the consumption of cannabis during pregnancy.

Endocannabinoid signaling in astrocytes

The study of the astrocytic contribution to brain functions has been growing in popularity in the neuroscience field. In the last years, and especially since the demonstration of the involvement of astrocytes in synaptic functions, the astrocyte field has revealed multiple functions of these cells that seemed inconceivable not long ago. In parallel, cannabinoid investigation has also identified different ways by which cannabinoids are able to interact with these cells, modify their functions, alter their communication with neurons and impact behavior. In this review, we will describe the expression of different endocannabinoid system members in astrocytes. Moreover, we will relate the latest findings regarding cannabinoid modulation of some of the most relevant astroglial functions, namely calcium (Ca²⁺ ) dynamics, gliotransmission, metabolism, and inflammation.

Cannabinoids—Perspectives for Individual Treatment in Selected Patients: Analysis of the Case Series

Cannabinoids can be successfully used in the treatment of many symptoms and diseases; however, most often they are not the drugs of first choice. They can be added to the primary therapy, which can improve its effectiveness, or be introduced as the basic treatment when the conventional methods have failed. Small clinical trials and case reports prove the benefits of applying medicinal cannabis in various indications; however, clinical trials in larger groups of patients are scarce and often controversial. Due to limited scientific evidence, it is essential to conduct further experimental trials. Understanding the role of endocannabinoids, as well as the composition of cannabis containing both phytocannabinoids and terpenes plays an important role in their clinical use. The clinical effects of cannabinoids depend, among other things, on the activity of the endocannabinoid system, the proportion of phytocannabinoids, such as Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD), and the dosage used. The article discusses the role of phytocannabinoids and the potential of using them in different clinical cases in patients suffering from chronic pain, opioid dependence, depression and migraine, who did not respond to the conventional therapeutic methods. In each of the presented cases, the implementation of cannabinoids altered the course of the disease and resulted in symptom relief. Every decision to introduce cannabinoids to the treatment should be made individually with careful attention paid to details. Additionally, it is worth taking care of good clinical communication and education so that the implemented therapy is safe, effective and properly perceived by the patient.

Cannabidiol enhancement of exposure therapy in treatment refractory patients with social anxiety disorder and panic disorder with agoraphobia: A randomised controlled trial

Preclinical research suggests that enhancing CB1 receptor agonism may improve fear extinction. In order to translate this knowledge into a clinical application we examined whether cannabidiol (CBD), a hydrolysis inhibitor of the endogenous CB1 receptor agonist anandamide (AEA), would enhance the effects of exposure therapy in treatment refractory patients with anxiety disorders. Patients with panic disorder with agoraphobia or social anxiety disorder were recruited for a double-blind parallel randomised controlled trial at three mental health care centres in the Netherlands. Eight therapist-assisted exposure in vivo sessions (weekly, outpatient) were augmented with 300 mg oral CBD (n = 39) or placebo (n = 41). The Fear Questionnaire (FQ) was assessed at baseline, mid- and post-treatment, and at 3 and 6 months follow-up. Primary analyses were on an intent-to-treat basis. No differences were found in treatment outcome over time between CBD and placebo on FQ scores, neither across (β = 0.32, 95% CI [-0.60; 1.25]) nor within diagnosis groups (β = -0.11, 95% CI [-1.62; 1.40]). In contrast to our hypotheses, CBD augmentation did not enhance early treatment response, within-session fear extinction or extinction learning. Incidence of adverse effects was equal in the CBD (n = 4, 10.3%) and placebo condition (n = 6, 15.4%). In this first clinical trial examining CBD as an adjunctive therapy in anxiety disorders, CBD did not improve treatment outcome. Future clinical trials may investigate different dosage regimens.

The CannTeen study: verbal episodic memory, spatial working memory, and response inhibition in adolescent and adult cannabis users and age-matched controls

BACKGROUND

Preclinical and human studies suggest that adolescent cannabis use may be associated with worse cognitive outcomes than adult cannabis use. We investigated the associations between chronic cannabis use and cognitive function in adolescent and adult cannabis users and controls. We hypothesised user-status would be negatively associated with cognitive function and this relationship would be stronger in adolescents than adults.

METHODS

As part of the 'CannTeen' project, this cross-sectional study assessed cognitive performance in adolescent cannabis users (n = 76; 16-17-year-olds), adolescent controls (n = 63), adult cannabis users (n = 71; 26-29-year-olds) and adult controls (n = 64). Users used cannabis 1-7 days/week. Adolescent and adult cannabis users were matched on cannabis use frequency (4 days/week) and time since last use (2.5 days). Verbal episodic memory (VEM) was assessed using the prose recall task, spatial working memory (SWM) was assessed using the spatial n-back task, and response inhibition was assessed with the stop-signal task. Primary outcome variables were: delayed recall, 3-back discriminability, and stop signal reaction time, respectively.

RESULTS

Users had worse VEM than controls (F(1,268) = 7.423, p = 0.007). There were no significant differences between user-groups on SWM or response inhibition. Null differences were supported by Bayesian analyses. No significant interactions between age-group and user-group were found for VEM, SWM, or response inhibition.

CONCLUSIONS

Consistent with previous research, there was an association between chronic cannabis use and poorer VEM, but chronic cannabis use was not associated with SWM or response inhibition. We did not find evidence for heightened adolescent vulnerability to cannabis-related cognitive impairment.

Endocannabinoid signaling in oligodendroglia

In the central nervous system, oligodendrocytes synthesize the myelin, a specialized membrane to wrap axons in a discontinuous way allowing a rapid saltatory nerve impulse conduction. Oligodendrocytes express a number of growth factors and neurotransmitters receptors that allow them to sense the environment and interact with neurons and other glial cells. Depending on the cell cycle stage, oligodendrocytes may respond to these signals by regulating their survival, proliferation, migration, and differentiation. Among these signals are the endocannabinoids, lipidic molecules synthesized from phospholipids in the plasma membrane in response to cell activation. Here, we discuss the evidence showing that oligodendrocytes express a full endocannabinoid signaling machinery involved in physiological oligodendrocyte functions that can be therapeutically exploited to promote remyelination in central nervous system pathologies.

Overview of Cannabis including Kampo Medicine and Therapy for Treatment of Dementia: A Review

Cannabis sativa L. is an annual herb oldest cultivated plants as a source of fiber since about 5000 B.C. On the other hand, the cannabis flower and seed are listed in Shennong's classic Materia Medica approximately 2000 years ago. The formulas prescribed with cannabis in Kampo medicine have been summarized. Cannabidiol (CBD) and tetrahydrocannabinol (THC) are the major neurological and psychiatric cannabinoids, and develop to drugs. It becomes evident that the therapeutic CBD and/or THC are the important candidate of anti-dementia drugs having different mechanism for Alzheimer's patients. Two receptors and endocannabinoids are also discussed for underlying mechanism of action. In order to promote the breeding of cannabis plant containing higher concentration of target cannabinoid the biosynthetic enzymes were isolated, cloning and the tertiary structure of THCA synthase determined by x-ray analysis resulting in the possibility of molecular breeding for cannabinoids.

Endocannabinoid system contributions to sex-specific adolescent neurodevelopment

With an increasing number of countries and states adopting legislation permitting the use of cannabis for medical purposes, there is a growing interest among health and research professionals into the system through which cannabinoids principally act, the endocannabinoid system (ECS). Much of the seminal research into the ECS dates back only 30 years and, although there has been tremendous development within the field during this time, many questions remain. More recently, investigations have emerged examining the contributions of the ECS to normative development and the effect of altering this system during important critical periods. One such period is adolescence, a unique period during which brain and behaviours are maturing and reorganizing in preparation for adulthood, including shifts in endocannabinoid biology. The purpose of this review is to discuss findings to date regarding the maturation of the ECS during adolescence and the consequences of manipulations of the ECS during this period to normative neurodevelopmental processes, as well as highlight sex differences in ECS function, important technical considerations, and future directions. Because most of what we know is derived from preclinical studies on rodents, we provide relevant background of this model and some commentary on the translational relevance of the research in this area.

Cannabidiol and the corticoraphe circuit in post-traumatic stress disorder

Post-Traumatic Stress Disorder (PTSD), characterized by re-experiencing, avoidance, negative affect, and impaired memory processing, may develop after traumatic events. PTSD is complicated by impaired plasticity and medial prefrontal cortex (mPFC) activity, hyperactivity of the amygdala, and impaired fear extinction. Cannabidiol (CBD) is a promising candidate for treatment due to its multimodal action that enhances plasticity and calms hyperexcitability. CBD’s mechanism in the mPFC of PTSD patients has been explored extensively, but literature on the mechanism in the dorsal raphe nucleus (DRN) is lacking. Following the PRISMA guidelines, we examined current literature regarding CBD in PTSD and overlapping symptomologies to propose a mechanism by which CBD treats PTSD via corticoraphe circuit. Acute CBD inhibits excess 5-HT release from DRN to amygdala and releases anandamide (AEA) onto amygdala inputs. By first reducing amygdala and DRN hyperactivity, CBD begins to ameliorate activity disparity between mPFC and amygdala. Chronic CBD recruits the mPFC, creating harmonious corticoraphe signaling. DRN releases enough 5-HT to ameliorate mPFC hypoactivity, while the mPFC continuously excites DRN 5-HT neurons via glutamate. Meanwhile, AEA regulates corticoraphe activity to stabilize signaling. AEA prevents DRN GABAergic interneurons from inhibiting 5-HT release so the DRN can assist the mPFC in overcoming its hypoactivity. DRN-mediated restoration of mPFC activity underlies CBD’s mechanism on fear extinction and learning of stress coping.

•

CBD reduces PTSD symptoms via the DRN and corticoraphe circuit.

•

Acute effects of CBD reduce DRN-amygdala excitatory signaling to lessen the activity disparity between amygdala and mPFC.

•

Chronic CBD officially resolves mPFC hypoactivity by facilitating 5-HT release from DRN to mPFC.

•

CBD-facilitated endocannabinoid signaling stabilizes DRN activity and restores mPFC inhibitory control.

•

Chronically administered CBD acts via the corticoraphe circuit to favor fear extinction over fear memory reconsolidation.

Activation of astroglial CB1R mediates cerebral ischemic tolerance induced by electroacupuncture

There are no effective treatments for stroke. The activation of endogenous protective mechanisms is a promising therapeutic approach, which evokes the intrinsic ability of the brain to protect itself. Accumulated evidence strongly suggests that electroacupuncture (EA) pretreatment induces rapid tolerance to cerebral ischemia. With regard to mechanisms underlying ischemic tolerance induced by EA, many molecules and signaling pathways are involved, such as the endocannabinoid system, although the exact mechanisms have not been fully elucidated. In the current study, we employed mutant mice, neuropharmacology, microdialysis, and virus transfection techniques in a middle cerebral artery occlusion (MCAO) model to explore the cell-specific and brain region-specific mechanisms of EA-induced neuroprotection. EA pretreatment resulted in increased ambient endocannabinoid (eCB) levels and subsequent activation of ischemic penumbral astroglial cannabinoid type 1 receptors (CB₁R) which led to moderate upregulation of extracellular glutamate that protected neurons from cerebral ischemic injury. These findings provide a novel cellular mechanism of EA and a potential therapeutic target for ischemic stroke.

Cannabidiol effectively reverses mechanical and thermal allodynia, hyperalgesia, and anxious behaviors in a neuropathic pain model: Possible role of CB1 and TRPV1 receptors

The incidence of chronic pain is high in the general population and it is closely related to anxiety disorders, which promote negative effects on the quality of life. The cannabinoid system has essential participation in the pain sensitivity circuit. In this perspective, cannabidiol (CBD) is considered a promising strategy for treating neuropathic pain. Our study aimed to evaluate the effects of sub-chronic systemic treatment with CBD (0.3, 3, 10, or 30 mg/kg, i.p.) in male in rats submitted to chronic constriction injury of the sciatic nerve (CCI) or not (SHAM) and assessed in nociceptive tests (von Frey, acetone, and hot plate, three days CBD's treatment) and in the open field test (OFT, two days CBD's treatment). We performed a screening immunoreactivity of CB1 and TRPV1 receptors in cortical and limbic regions tissues, which were collected after 1.5 h of behavioral tests on the 24th experimental day. This study presents a dose-response curve to understand better the effects of low doses (3 mg/kg) on CBD's antiallodynic and anxiolytic effects. Also, low doses of CBD were able to (1) reverse mechanical and thermal allodynia (cold) and hyperalgesia, (2) reverse anxious behaviors (reduction of the % of grooming and freezing time, and increase of the % of center time in the OFT) induced by chronic pain. The peripheral neuropathy promoted the increase in the expression of CB1 and TRPV1 receptors in the anterior cingulate cortex (ACC), anterior insular cortex (AIC), basolateral amygdala (BLA), dorsal hippocampus (DH), and ventral hippocampus (VH). CBD potentiated this effect in the ACC, AIC, BLA, DH, and VH regions. These results provide substantial evidence of the role of the ACC-AIC-BLA corticolimbic circuit, and BLA-VH for pain regulation. These results can be clinically relevant since they contribute to the evidence of CBD's beneficial effects on treating chronic pain and associated comorbidities such as anxiety.

Cannabinoids Regulate Sensory Processing in Early Olfactory and Visual Neural Circuits

Our sensory systems such as the olfactory and visual systems are the target of neuromodulatory regulation. This neuromodulation starts at the level of sensory receptors and extends into cortical processing. A relatively new group of neuromodulators includes cannabinoids. These form a group of chemical substances that are found in the cannabis plant. Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD) are the main cannabinoids. THC acts in the brain and nervous system like the chemical substances that our body produces, the endogenous cannabinoids or endocannabinoids, also nicknamed the brain's own cannabis. While the function of the endocannabinoid system is understood fairly well in limbic structures such as the hippocampus and the amygdala, this signaling system is less well understood in the olfactory pathway and the visual system. Here, we describe and compare endocannabinoids as signaling molecules in the early processing centers of the olfactory and visual system, the olfactory bulb, and the retina, and the relevance of the endocannabinoid system for synaptic plasticity.

Cannabinoids and sleep-wake cycle: The potential role of serotonin

Cannabis sativa (Marijuana) has a long history as a medicinal plant and Δ9-tetrahydrocannabinol (Δ9-THC) is the most active component in this plant. Cannabinoids are interesting compounds with various modulatory effects on physiological processes and cognitive functions. The use of cannabinoids is a double-edged sword, because they induce both adverse and therapeutic properties. One of the most important roles of cannabinoids is modulating sleep-wake cycle. Sleep, its cycle, and its mechanism are highly unknown. Also, the effects of cannabinoids on sleep-wake cycle are so inconsistent. Thus, understanding the role of cannabinoids in modulating sleep-wake cycle is a critical scientific goal. Cannabinoids interact with many neurotransmitter systems. In this review article, we chose serotonin due to its important role in regulating sleep-wake cycle. We found that the interaction between cannabinoids and serotonergic signaling especially in the dorsal raphe is extensive, unknown, and controversial.

CB1R-dependent regulation of astrocyte physiology and astrocyte-neuron interactions

The endocannabinoid system (ECS) is involved in a variety of brain functions, mainly through the activation of the type-1 cannabinoid receptors (CB1R). CB1R are highly expressed throughout the brain at different structural, cellular and subcellular locations and its activity and expression levels have a direct impact in synaptic activity and behavior. In the last few decades, astrocytes have arisen as active players of brain physiology through their participation in the tripartite synapse and through their metabolic interaction with neurons. Here, we discuss some of the mechanisms by which astroglial CB1R at different subcellular locations, regulate astrocyte calcium signals and have an impact on gliotransmission and metabolic regulation. In addition, we discuss evidence pointing at astrocytes as potential important sources of endocannabinoid synthesis and release. Thus, we summarize recent findings that add further complexity and establish that the ECS is a fundamental effector of astrocyte functions in the brain. This article is part of the special issue on 'Cannabinoids'.

Changes in sleep-wake cycle after microinjection of agonist and antagonist of endocannabinoid receptors at the medial septum of rats

The role of medial septum in the genesis of slow-wave sleep and the inhibition of rapid eye movement sleep has been established using neurotoxic lesion and chemical stimulation of the medial septum. Intracerebroventricular injection of endocannabinoids (anandamide) decreases wake and increases slow-wave and rapid eye movement sleep in rats. Central cannabinoid (CB1) receptors are localized in the rat medial septum; however, the role of cannabinoid receptors at the medial septum on the regulation of sleep-wakefulness in rats lacks evidence. In this study, we have examined the changes in sleep architecture of 21 male Wistar rats, divided into three groups. Initially, 6 rats were used for dose standardization. Subsequently, one group (n = 6) was microinjected with CB1 receptor agonist, R-(+)-WIN 55,212-2 mesylate salt, the second group (n = 6) received microinjection of CB1 receptor antagonist LY 320,135, and the third group (n = 5) was microinjected with the vehicle, DMSO at the medial septum using stereotaxy. The sleep-wake cycle was recorded using electroencephalogram, electro-oculogram, and electromyogram. Microinjection of CB1 receptor agonist at the medial septum decreased slow-wave sleep and increased total sleep time. The increase in total sleep time was due to an increased percentage of rapid eye movement sleep. After the third and fourth hour of CB1 receptor antagonist microinjection at the medial septum, slow-wave sleep decreased when compared to vehicle injection, while rapid eye movement sleep decreased compared to baseline. We conclude that the endocannabinoid system at the septal nucleus acts through CB1 receptors to increase rapid eye movement sleep in rats.

Distribution of the Cannabinoid Receptor Type 1 in the Brain of the Genetically Audiogenic Seizure-Prone Hamster GASH/Sal

The endocannabinoid system modulates epileptic seizures by regulating neuronal excitability. It has become clear that agonist activation of central type I cannabinoid receptors (CB1R) reduces epileptogenesis in pre-clinical animal models of epilepsy. The audiogenic seizure-prone hamster GASH/Sal is a reliable experimental model of generalized tonic-clonic seizures in response to intense sound stimulation. However, no studies hitherto had investigated CB1R in the GASH/Sal. Although the distribution of CB1R has been extensively studied in mammalian brains, their distribution in the Syrian golden hamster brain also remains unknown. The objective of this research is to determine by immunohistochemistry the differential distribution of CB1R in the brains of GASH/Sal animals under seizure-free conditions, by comparing the results with wild-type Syrian hamsters as controls. CB1R in the GASH/Sal showed a wide distribution in many nuclei of the central nervous system. These patterns of CB1R-immunolabeling are practically identical between the GASH/Sal model and control animals, varying in the intensity of immunostaining in certain regions, being slightly weaker in the GASH/Sal than in the control, mainly in brain regions associated with epileptic networks. The RT-qPCR analysis confirms these results. In summary, our study provides an anatomical basis for further investigating CB1R in acute and kindling audiogenic seizure protocols in the GASH/Sal model as well as exploring CB1R activation via exogenously administered cannabinoid compounds.

Effects of Cannabis Consumption on Sleep

Despite the fact that medical properties of Cannabis have been recognized for more than 5000 years, the use of Cannabis for medical purposes have recently reemerged and became more accessible. Cannabis is usually employed as a self-medication for the treatment of insomnia disorder. However, the effects of Cannabis on sleep depend on multiple factors such as metabolomic composition of the plant, dosage and route of administration. In the present chapter, we reviewed the main effect Cannabis on sleep. We focused on the effect of "crude or whole plant" Cannabis consumption (i.e., smoked, oral or vaporized) both in humans and experimental animal models.The data reviewed establish that Cannabis modifies sleep. Furthermore, a recent experimental study in animals suggests that vaporization (which is a recommended route for medical purposes) of Cannabis with high THC and negligible CBD, promotes NREM sleep. However, it is imperative to perform new clinical studies in order to confirm if the administration of Cannabis could be a beneficial therapy for the treatment of sleep disorders.

Endocannabinoid-serotonin systems interaction in health and disease

Endocannabinoid (eCB) and serotonin (5-HT) neuromodulatory systems work both independently and together to finely orchestrate neuronal activity throughout the brain to strongly sculpt behavioral functions. Surprising parallelism between the behavioral effects of 5-HT and eCB activity has been widely reported, including the regulation of emotional states, stress homeostasis, cognitive functions, food intake and sleep. The distribution pattern of the 5-HT system and the eCB molecular elements in the brain display a strong overlap and several studies report a functional interplay and even a tight interdependence between eCB/5-HT signaling. In this review, we examine the available evidence of the interaction between the eCB and 5-HT systems. We first introduce the eCB system, then we describe the eCB/5-HT crosstalk at the neuronal and synaptic levels. Finally, we explore the potential eCB/5-HT interaction at the behavioral level with the implication for psychiatric and neurological disorders. The precise elucidation of how this neuromodulatory interaction dynamically regulates biological functions may lead to the development of more targeted therapeutic strategies for the treatment of depressive and anxiety disorders, psychosis and epilepsy.

Modulation of Noradrenergic and Serotonergic Systems by Cannabinoids: Electrophysiological, Neurochemical and Behavioral Evidence

The main noradrenergic and serotonergic nuclei in the central nervous system (CNS) are the locus coeruleus (LC) and the dorsal raphe nucleus (DRN). These brain areas, located in the brainstem, play a pivotal role in the control of various functions and behaviors that are altered by cannabinoids (i.e., pain, arousal, mood, anxiety, or sleep-wake cycle). Anatomical, neurochemical, and functional data suggest that cannabinoids regulate both central noradrenergic and serotonergic neurotransmission. Thus, strong evidence has shown that the firing activity of LC and DRN monoamine neurons or the synthesis/release of noradrenaline (NA) and serotonin (5-HT) in the projection areas are all affected by cannabinoid administration. Herein, we propose that interaction between the endocannabinoid system and the noradrenergic-serotonergic systems could account for some of the anxiolytic, antidepressant, and antinociceptive effects of cannabinoids or the disruption of attention/sleep induced by these drugs.

On the Role of Central Type-1 Cannabinoid Receptor Gene Regulation in Food Intake and Eating Behaviors

Different neuromodulatory systems are involved in long-term energy balance and body weight and, among these, evidence shows that the endocannabinoid system, in particular the activation of type-1 cannabinoid receptor, plays a key role. We here review current literature focusing on the role of the gene encoding type-1 cannabinoid receptors in the CNS and on the modulation of its expression by food intake and specific eating behaviors. We point out the importance to further investigate how environmental cues might have a role in the development of obesity as well as eating disorders through the transcriptional regulation of this gene in order to prevent or to treat these pathologies.

Cannabinoid Receptors: An Update on Cell Signaling, Pathophysiological Roles and Therapeutic Opportunities in Neurological, Cardiovascular, and Inflammatory Diseases

The identification of the human cannabinoid receptors and their roles in health and disease, has been one of the most significant biochemical and pharmacological advancements to have occurred in the past few decades. In spite of the major strides made in furthering endocannabinoid research, therapeutic exploitation of the endocannabinoid system has often been a challenging task. An impaired endocannabinoid tone often manifests as changes in expression and/or functions of type 1 and/or type 2 cannabinoid receptors. It becomes important to understand how alterations in cannabinoid receptor cellular signaling can lead to disruptions in major physiological and biological functions, as they are often associated with the pathogenesis of several neurological, cardiovascular, metabolic, and inflammatory diseases. This review focusses mostly on the pathophysiological roles of type 1 and type 2 cannabinoid receptors, and it attempts to integrate both cellular and physiological functions of the cannabinoid receptors. Apart from an updated review of pre-clinical and clinical studies, the adequacy/inadequacy of cannabinoid-based therapeutics in various pathological conditions is also highlighted. Finally, alternative strategies to modulate endocannabinoid tone, and future directions are also emphasized.

Neural and behavioral correlates associated with adolescent marijuana use

Purpose of Review

Marijuana (MJ) is one of the most commonly used drugs among adolescents. Exposure to MJ during adolescence can lead to alterations in brain development, and, subsequently to the behavioral correlates regulated by the affected brain regions. In this review, we discuss findings from preclinical and human studies examining the relationship between adolescent MJ use and the neurobiological and behavioral correlates associated with it.

Recent Findings

Current findings indicate that adolescent MJ use is associated with alterations in brain structure and function, especially in regions that express high levels of the cannabinoid 1 receptor such as the prefrontal cortex, hippocampus, cerebellum and limbic regions. These alterations are correlated with changes in affective, cognitive and reward-seeking behavior. Furthermore, evidence suggests that exposure to MJ during adolescence can have long-lasting and pronounced neural and behavioral effects into adulthood.

Summary

The wide ranging neural and behavioral correlates associated with MJ use during adolescence highlight the need for further studies to better understand the potential risk factors and/or neurotoxic effects of adolescent MJ use.

An investigation of the relationship between glutamate and resting state connectivity in chronic cannabis users

Human and animal studies have shown that heavy cannabis (CB) use interacts with glutamatergic signaling. Additionally, recent studies have suggested that glutamate (Glu) may drive resting state functional connectivity (RSfc). The aims of the current preliminary study were to: 1) determine whether dorsal anterior cingulate cortex (dACC) Glu is related to RSfc between the dACC and two nodes of the reward network, the nucleus accumbens (NAc) and hippocampus (Hp); and 2) determine whether CB use interacts with the relationship between dACC Glu and RSfc. A group of 23 chronic CB users and 23 healthy controls participated in this multimodal MRI study. Glu levels were assessed in the dACC using magnetic resonance spectroscopy (MRS). Linear regression models were used to determine whether dACC Glu and CB use predicts RSfc between the dACC and the NAc and Hp. While the effect size is small, the results showed that the connectivity between the dACC and right NAc was predicted by the interaction between dACC Glu levels and monthly CB use. Additionally, while there is some suggestion that dACC Glu is correlated with dACC-hippocampal connectivity, unlike for dACC/NAc connectivity the relationship between them does not appear to be affected by CB use. These preliminary findings are significant in that they demonstrate the need for future studies with larger sample sizes to better characterize the relationship between resting state connectivity and neurochemistry as well as to characterize how CB use interacts with that relationship.

Receptors and Channels Possibly Mediating the Effects of Phytocannabinoids on Seizures and Epilepsy

Epilepsy contributes to approximately 1% of the global disease burden. By affecting especially young children as well as older persons of all social and racial variety, epilepsy is a present disorder worldwide. Currently, only 65% of epileptic patients can be successfully treated with antiepileptic drugs. For this reason, alternative medicine receives more attention. Cannabis has been cultivated for over 6000 years to treat pain and insomnia and used since the 19th century to suppress epileptic seizures. The two best described phytocannabinoids, (−)-trans-Δ⁹-tetrahydrocannabinol (THC) and cannabidiol (CBD) are claimed to have positive effects on different neurological as well as neurodegenerative diseases, including epilepsy. There are different cannabinoids which act through different types of receptors and channels, including the cannabinoid receptor 1 and 2 (CB₁, CB₂), G protein-coupled receptor 55 (GPR55) and 18 (GPR18), opioid receptor µ and δ, transient receptor potential vanilloid type 1 (TRPV1) and 2 (TRPV2), type A γ-aminobutyric acid receptor (GABA_AR) and voltage-gated sodium channels (VGSC). The mechanisms and importance of the interaction between phytocannabinoids and their different sites of action regarding epileptic seizures and their clinical value are described in this review.

Functional role for preoptic CB1 receptors in breathing and thermal control

The anteroventral preoptic region (AVPO) of the hypothalamus is involved in both temperature and breathing regulation. This area densely express cannabinoid receptors type 1 (CB1) that modulate both excitatory and inhibitory synaptic transmission. However, it is still unknown if the endocannabinoid system located in the AVPO participates in breathing control and thermoregulation. Therefore, we tested the participation of CB1 in the AVPO in the modulation of ventilation and thermal control during normoxia and hypoxia. To this end, body temperature (Tb) of Wistar rats was monitored by datallogers and ventilation (V_E) by whole body plethysmography before and after intra-AVPO microinjection of AM-251 (CB1 antagonist, 50 and 100 pmol) followed by 60 min of hypoxia exposure (7% O₂). Intra-AVPO microinjection of the higher dose of AM-251 increased V_E but did not change Tb under resting conditions. Exposure of rats to 7% of inspired oxygen evoked typical hypoxia-induced anapyrexia and hyperventilation after vehicle microinjection. The higher dose of the cannabinoid antagonist increased the hypoxia-induced hyperventilation, in the same magnitude as observed under normoxic condition, whereas the drop in Tb elicited by hypoxia was attenuated. Therefore, the present results demonstrate that the endocannabinoid system acting on CB1 receptors in the AVPO exerts a tonic inhibitory modulation on breathing but seem not be involved in thermoregulation during resting conditions. In addition, activation of CB1 receptors in the AVPO stimulate thermal response during hypoxia, reducing energetically expensive responses, such as the hypoxic hyperventilation.

Cannabinoids, Chemical Senses, and Regulation of Feeding Behavior

The herb Cannabis sativa has been traditionally used in many cultures and all over the world for thousands of years as medicine and recreation. However, because it was brought to the Western world in the late 19th century, its use has been a source of controversy with respect to its physiological effects as well as the generation of specific behaviors. In this regard, the CB1 receptor represents the most relevant target molecule of cannabinoid components on nervous system and whole-body energy homeostasis. Thus, the promotion of CB1 signaling can increase appetite and stimulate feeding, whereas blockade of CB1 suppresses hunger and induces hypophagia. Taste and flavor are sensory experiences involving the oral perception of food-derived chemicals and drive a primal sense of acceptable or unacceptable for what is sampled. Therefore, research within the last decades focused on deciphering the effect of cannabinoids on the chemical senses involved in food perception and consequently in the pattern of feeding. In this review, we summarize the data on the effect of cannabinoids on chemical senses and their influences on food intake control and feeding behavior.

Monoacylglycerol lipase alpha inhibition alters prefrontal cortex excitability and blunts the consequences of traumatic stress in rat

Neural activity within the ventromedial prefrontal cortex (vmPFC) is a critical determinant of stressor-induced anxiety. Pharmacological activation of the vmPFC during stress protects against stress-induced social anxiety suggesting that altering the excitatory/inhibitory (E/I) tone in the vmPFC may promote stress resilience. E/I balance is maintained, in part, by endogenous cannabinoid (eCB) signaling with the calcium dependent retrograde release of 2-arachidonoylglycerol (2-AG) suppressing presynaptic neurotransmitter release. We hypothesized that raising 2-AG levels, via inhibition of its degradation enzyme monoacylglycerol lipase (MAGL) with KML29, would shift vmPFC E/I balance and promote resilience. In acute slice experiments, bath application of KML29 (100 nM) augmented evoked excitatory neurotransmission as evidenced by a left-shift in fEPSP I/O curve, and decreased sIPSC amplitude. In whole-cell recordings, KML29 increased resting membrane potential but reduced the after depolarization, bursting rate, membrane time constant and slow after hyperpolarization. Intra-vmPFC administration of KML29 (200ng/0.5μL/hemisphere) prior to inescapable stress (IS) exposure (25, 5s tail shocks) prevented stress induced anxiety as measured by juvenile social exploration 24 h after stressor exposure. Conversely, systemic administration of KML29 (40 mg/kg, i.p.) 2 h before IS exacerbated stress induced anxiety. MAGL inhibition in the vmPFC may promote resilience by augmenting the output of neurons that project to brainstem and limbic structures that mediate stress responses.

Cannabis Use and Consequences

As an increasing number of states legalize cannabis use for recreational and/or medical purposes, it is increasingly important to understand the neural and cognitive consequences of recreational cannabis use in adolescent consumers. Adolescence is marked by ongoing neuromaturational processes, making this a particularly vulnerable period, particularly regarding exposure to drugs, including cannabis. This review highlights evidence from studies documenting the neural impact of cannabis use in adolescence and explores mediating factors related to cannabis use.

Cannabidiol and Cannabinoid Compounds as Potential Strategies for Treating Parkinson's Disease and L-DOPA-Induced Dyskinesia

Parkinson's disease (PD) and L-DOPA-induced dyskinesia (LID) are motor disorders with significant impact on the patient's quality of life. Unfortunately, pharmacological treatments that improve these disorders without causing severe side effects are not yet available. Delay in initiating L-DOPA is no longer recommended as LID development is a function of disease duration rather than cumulative L-DOPA exposure. Manipulation of the endocannabinoid system could be a promising therapy to control PD and LID symptoms. In this way, phytocannabinoids and synthetic cannabinoids, such as cannabidiol (CBD), the principal non-psychotomimetic constituent of the Cannabis sativa plant, have received considerable attention in the last decade. In this review, we present clinical and preclinical evidence suggesting CBD and other cannabinoids have therapeutic effects in PD and LID. Here, we discuss CBD pharmacology, as well as its neuroprotective effects and those of other cannabinoids. Finally, we discuss the modulation of several pro- or anti-inflammatory factors as possible mechanisms responsible for the therapeutic/neuroprotective potential of Cannabis-derived/cannabinoid synthetic compounds in motor disorders.

Cannabidiol attenuates aggressive behavior induced by social isolation in mice: Involvement of 5-HT1A and CB1 receptors

Long-term single housing increases aggressive behavior in mice, a condition named isolation-induced aggression or territorial aggression, which can be attenuated by anxiolytic, antidepressant, and antipsychotic drugs. Preclinical and clinical findings indicate that cannabidiol (CBD), a non-psychotomimetic compound from Cannabis sativa, has anxiolytic, antidepressant, and antipsychotic properties. Few studies, however, have investigated the effects of CBD on aggressive behaviors. Here, we investigated whether CBD (5, 15, 30, and 60 mg/kg; i.p.) could attenuate social isolation-induced aggressive behavior in the resident-intruder test. Male Swiss mice (7-8 weeks) were single-housed for 10 days (resident mice) to induce aggressive behaviors, while conspecific mice of same sex and age (intruder mice) were group-housed. During the test, the intruder was placed into the resident's home-cage and aggressive behaviors initiated by the resident, including the latency for the first attack, number of attacks, and total duration of aggressive encounters, were recorded. The involvement of 5-HT1A and CB1 receptors (CB1R) in the effects of CBD was also investigated. All tested CBD doses induced anti-aggressive effects, indicated by a decrease in the number of attacks. CBD, at intermediary doses (15 and 30 mg/kg), also increased latency to attack the intruder and decreased the duration of aggressive encounters. No CBD dose interfered with locomotor behavior. CBD anti-aggressive effects were attenuated by the 5-HT1A receptor antagonist WAY100635 (0.3 mg/kg) and the CB1 antagonist AM251 (1 mg/kg), suggesting that CBD decreases social isolation-induced aggressive behaviors through a mechanism associated with the activation of 5-HT1A and CB1 receptors. Also, CBD decreased c-Fos protein expression, a neuronal activity marker, in the lateral periaqueductal gray (lPAG) in social-isolated mice exposed to the resident-intruder test, indicating a potential involvement of this brain region in the drug effects. Taken together, our findings suggest that CBD may be therapeutically useful to treat aggressive behaviors that are usually associated with psychiatric disorders.

Cannabinoid receptor-mediated modulation of inhibitory inputs to mitral cells in the main olfactory bulb

The endocannabinoid (eCB) signaling system has been functionally implicated in many brain regions. Our understanding of the role of cannabinoid receptor type 1 (CB1) in olfactory processing remains limited. Cannabinoid signaling is involved in regulating glomerular activity in the main olfactory bulb (MOB). However, the cannabinoid-related circuitry of inputs to mitral cells in the MOB has not been fully determined. Using anatomical and functional approaches we have explored this question. CB1 was present in periglomerular processes of a GAD65-positive subpopulation of interneurons but not in mitral cells. We detected eCBs in the mouse MOB as well as the expression of CB1 and other genes associated with cannabinoid signaling in the MOB. Patch-clamp electrophysiology demonstrated that CB1 agonists activated mitral cells and evoked an inward current, while CB1 antagonists reduced firing and evoked an outward current. CB1 effects on mitral cells were absent in subglomerular slices in which the olfactory nerve layer and glomerular layer were removed, suggesting the glomerular layer as the site of CB1 action. We previously observed that GABAergic periglomerular cells show the inverse response pattern to CB1 activation compared with mitral cells, suggesting that CB1 indirectly regulates mitral cell activity as a result of cellular activation of glomerular GABAergic processes . This hypothesis was supported by the finding that cannabinoids modulated synaptic transmission to mitral cells. We conclude that CB1 directly regulates GABAergic processes in the glomerular layer to control GABA release and, in turn, regulates mitral cell activity with potential effects on olfactory threshold and behavior.NEW & NOTEWORTHY Cannabinoid signaling with cannabinoid receptor type 1 (CB1) is involved in the regulation of glomerular activity in the main olfactory bulb (MOB). We detected endocannabinoids in the mouse MOB. CB1 was present in periglomerular processes of a GAD65-positive subpopulation of interneurons. CB1 agonists activated mitral cells. CB1 directly regulates GABAergic processes to control GABA release and, in turn, regulates mitral cell activity with potential effects on olfactory threshold and behavior.

Retrograde activation of CB1R by muscarinic receptors protects against central organophosphorus toxicity

The acute toxicity of organophosphorus-based compounds is primarily a result of acetylcholinesterase inhibition in the central and peripheral nervous systems. The resulting cholinergic crisis manifests as seizure, paralysis, respiratory failure and neurotoxicity. Though overstimulation of muscarinic receptors is the mechanistic basis of central organophosphorus (OP) toxicities, short-term changes in synapse physiology that precede OP-induced seizures have not been investigated in detail. To study acute effects of OP exposure on synaptic function, field excitatory postsynaptic potentials (fEPSPs) were recorded from Schaffer collateral synapses in the mouse hippocampus CA1 stratum radiatum during perfusion with various OP compounds. Administration of the OPs paraoxon, soman or VX rapidly and stably depressed fEPSPs via a presynaptic mechanism, while the non-OP proconvulsant tetramethylenedisulfotetramine had no effect on fEPSP amplitudes. OP-induced presynaptic long-term depression manifested prior to interictal spiking, occurred independent of recurrent firing, and did not require NMDA receptor currents, suggesting that it was not mediated by activity-dependent calcium uptake. Pharmacological dissection revealed that the presynaptic endocannabinoid type 1 receptor (CB1R) as well as postsynaptic M₁ and M₃ muscarinic acetylcholine receptors were necessary for OP-LTD. Administration of CB1R antagonists significantly reduced survival in mice after a soman challenge, revealing an acute protective role for endogenous CB1R signaling during OP exposure. Collectively these data demonstrate that the endocannabinoid system alters glutamatergic synaptic function during the acute response to OP acetylcholinesterase inhibitors.

The Modulating Role of Sex and Anabolic-Androgenic Steroid Hormones in Cannabinoid Sensitivity

Cannabis is the most commonly used illicit drug worldwide. Although its use is associated with multiple adverse health effects, including the risk of developing addiction, recreational and medical cannabis use is being increasing legalized. In addition, use of synthetic cannabinoid drugs is gaining considerable popularity and is associated with mass poisonings and occasional deaths. Delineating factors involved in cannabis use and addiction therefore becomes increasingly important. Similarly to other drugs of abuse, the prevalence of cannabis use and addiction differs remarkably between males and females, suggesting that sex plays a role in regulating cannabinoid sensitivity. Although it remains unclear how sex may affect the initiation and maintenance of cannabis use in humans, animal studies strongly suggest that endogenous sex hormones modulate cannabinoid sensitivity. In addition, synthetic anabolic-androgenic steroids alter substance use and further support the importance of sex steroids in controlling drug sensitivity. The recent discovery that pregnenolone, the precursor of all steroid hormones, controls cannabinoid receptor activation corroborates the link between steroid hormones and the endocannabinoid system. This article reviews the literature regarding the influence of endogenous and synthetic steroid hormones on the endocannabinoid system and cannabinoid action.

Migraine, Cyclic Vomiting Syndrome, and Other Gastrointestinal Disorders

PURPOSE OF REVIEW

Cyclic vomiting syndrome (CVS) is a chronic functional gastrointestinal disorder characterized by episodic nausea and vomiting and is diagnosed using Rome IV criteria. CVS is being recognized more frequently in adults with a prevalence of 2%. It is associated with several functional disorders like autonomic dysfunction, anxiety, and depression, but the strongest association is with migraine. We will elucidate the close relationship between migraine and CVS and briefly discuss its association with other gastrointestinal disorders.

RECENT FINDINGS

We highlight similarities in pathophysiology, clinical presentation, and response to medications between CVS and migraine (tricyclic antidepressants, triptans, antiepileptics). We also discuss novel therapies like CGRP inhibitors which are effective in migraine and have potential for adaptation in patients with CVS. Using migraine as a template should enable investigators to elucidate the mechanisms underlying this disorder, develop novel therapies, and direct future research in CVS.

Prefrontal endocannabinoids, stress controllability and resilience: A hypothesis

Stressor exposure is a predisposing risk factor for many psychiatric conditions such as PTSD and depression. However, stressors do not influence all individuals equally and in response to an identical stressor some individuals may be vulnerable while others are resilient. While various biological and behavioral factors contribute to vulnerability versus resilience, an individual's degree of control over the stressor is among the most potent. Even with only one experience with control over stress, behavioral control has been shown to have acute and long-lasting stress-mitigating effects. This suggests that control both blunts the response to acute stress and prepares the subject to be resilient to future stressors. In this review, we first summarize the evidence which suggests the ventromedial prefrontal cortex (vmPFC) is a critical component of stressor controllability circuits and a locus of neuroplasticity supporting the acute and long-lasting consequences of control. We next review the central endocannabinoid (eCB) system as a possible mediator of short and long-term synaptic transmission in the vmPFC, and offer a hypothesis whereby eCBs regulate vmPFC circuits engaged when a subject has control over stress and may contribute to the encoding of acute stress coping into long lasting stressor resilience.

Endocannabinoid CB1 receptors are involved in antiepileptogenic effect of low frequency electrical stimulation during perforant path kindling in rats

INTRODUCTION

Administration of low-frequency electrical stimulation (LFS) at the kindling site has an antiepileptogenic effect. In the present study, we investigated the role of cannabinoid receptors type 1 (CB1) in mediating the inhibitory effects of LFS on the development of perforant path kindled seizures.

METHODS

For seizure generation, rats were kindled by electrical stimulation of perforant path in semi-rapid kindling manner (12 stimulations per day at 10 min intervals at afterdischarge threshold intensity).To determine the effect of LFS (0.1 ms pulse duration at 1 Hz, 800 pulses) on seizure generation, LFS was applied to the perforant path 5 min after the last kindling stimulation daily. AM281, a CB1 receptor antagonist, was microinjected into the lateral ventricle immediately after the last kindling stimulation (before LFS application) at the doses of 0.5 and 2 μg/μl during kindling procedure. The expression of cannabinoid receptors in the dentate gyrus was also investigated using immunohistochemistry.

RESULTS

Application of LFS had inhibitory effect on development of kindled seizures (kindling rate). Microinjection of AM281 (0.5 μg/μl) immediately after the last kindling stimulation (before LFS application) reduced the inhibitory effect of LFS on the kindling rate and suppressed the effects of LFS on potentiation (increasing the magnitude) of both population spike amplitude and population excitatory postsynaptic potential slope during kindling acquisition. AM281 pretreatment also prevented the effects of LFS on kindling-induced increase in early and late paired pulse depression. The higher dose of AM281 (2 μg/μl) failed to exert the effects observed with its lower dose (0.5 μg/μl). In addition, there was a decreased CB1 receptors immunostaining in kindled animals compared to control. However, application of LFS following kindling stimulations led to overexpression of CB1 receptors in the dentate gyrus.

CONCLUSION

Obtained results showed that activation of overexpressed cannabinoid CB1 receptors by endogenous cannabinoids may have a role in mediating the inhibitory effect of LFS on perforant path kindled seizures.

The Neuroglial Dialog Between Cannabinoids and Hemichannels

The formation of gap junctions was initially thought to be the central role of connexins, however, recent evidence had brought to light the high relevance of unopposed hemichannels as an independent mechanism for the selective release of biomolecules during physiological and pathological conditions. In the healthy brain, the physiological opening of astrocyte hemichannels modulates basal excitatory synaptic transmission. At the other end, the release of potentially neurotoxic compounds through astroglial hemichannels and pannexons has been insinuated as one of the functional alterations that negatively affect the progression of multiple brain diseases. Recent insights in this matter have suggested encannabinoids (eCBs) as molecules that could regulate the opening of these channels during diverse conditions. In this review, we discuss and hypothesize the possible interplay between the eCB system and the hemichannel/pannexon-mediated signaling in the inflamed brain and during event of synaptic plasticity. Most findings indicate that eCBs seem to counteract the activation of major neuroinflammatory pathways that lead to glia-mediated production of TNF-α and IL-1β, both well-known triggers of astroglial hemichannel opening. In contrast to the latter, in the normal brain, eCBs apparently elicit the Ca²⁺-activation of astrocyte hemichannels, which could have significant consequences on eCB-dependent synaptic plasticity.

Endocannabinoid System and Migraine Pain: An Update

The trigeminovascular system (TS) activation and the vasoactive release from trigeminal endings, in proximity of the meningeal vessels, are considered two of the main effector mechanisms of migraine attacks. Several other structures and mediators are involved, however, both upstream and alongside the TS. Among these, the endocannabinoid system (ES) has recently attracted considerable attention. Experimental and clinical data suggest indeed a link between dysregulation of this signaling complex and migraine headache. Clinical observations, in particular, show that the levels of anandamide (AEA)—one of the two primary endocannabinoid lipids—are reduced in cerebrospinal fluid and plasma of patients with chronic migraine (CM), and that this reduction is associated with pain facilitation in the spinal cord. AEA is produced on demand during inflammatory conditions and exerts most of its effects by acting on cannabinoid (CB) receptors. AEA is rapidly degraded by fatty acid amide hydrolase (FAAH) enzyme and its levels can be modulated in the peripheral and central nervous system (CNS) by FAAH inhibitors. Inhibition of AEA degradation via FAAH is a promising therapeutic target for migraine pain, since it is presumably associated to an increased availability of the endocannabinoid, specifically at the site where its formation is stimulated (e.g., trigeminal ganglion and/or meninges), thus prolonging its action.