Effects of long-term exposure to delta9-THC on expression of cannabinoid receptor (CB1) mRNA in different rat brain regions

Endocannabinoid administration affects taste preference and the expression of cannabinoid and opioid receptors in the amygdala of early lactating cows

The aim of the study was to investigate the influence of intraperitoneal N-arachidonoylethanolamide (AEA) on taste preference for feed and water, tongue taste receptor signalling (TAS1R2, GNAT3), and endocannabinoid (CNR1, CNR2, GPR55) and opioid (OPRD1, OPRK1, OPRM1, OPRL1) receptors in the amygdala and nucleus accumbens in periparturient cows. We conducted taste preference tests using unaltered, umami-tasting, and sweet-tasting water and feed, before and after calving. After calving, eight cows received AEA injections (3 µg/(kg bodyweight × day), 25 days), whereas eight control (CON) cows received saline injections. Tissue was sampled 30 days after calving. Before calving, both cow groups preferred sweet-tasting feed and umami-tasting water. After calving, only the AEA-treated group preferred sweet-tasting feed, whereas the CON group showed no clear taste preference. In the amygdala, the mRNA expression of CNR1, OPRD1 (left hemisphere) and OPRK1 (right hemisphere) was lower in AEA animals than in CON animals, whereas no differences were found in the nucleus accumbens and tongue taste receptor expression. In conclusion, AEA administration enhanced existing taste preferences and reduced the expression of specific endocannabinoid and opioid receptors in the amygdala. The results support endocannabinoid-opioid interactions in the control of taste-dependent feed preference in early lactating cows.

Investigating the "two-hit hypothesis": Effects of prenatal maternal immune activation and adolescent cannabis use on neurodevelopment in mice

Prenatal exposure to maternal immune activation (MIA) and chronic adolescent cannabis use are both risk factors for neuropsychiatric disorders. However, exposure to a single risk factor may not result in major mental illness, indicating that multiple exposures may be required for illness onset. Here, we examine whether combined exposure to prenatal MIA and adolescent delta-9-tetrahydrocannabinol (THC), the main psychoactive component of cannabis, lead to enduring neuroanatomical and behavioural changes in adulthood. Mice were prenatally exposed to viral mimetic, poly I:C (5 mg/kg), or vehicle at gestational day (GD) 9, and postnatally exposed to chronic THC (5 mg/kg, intraperitoneal) or vehicle during adolescence (postnatal day [PND]28-45). Longitudinal magnetic resonance imaging (MRI) was performed pre-treatment, PND 25, post-treatment, PND 50, and in adulthood, PND85, followed by behavioural tests for anxiety-like, social, and sensorimotor gating. Post-mortem assessment of cannabinoid (CB)1 and 2 receptor expressing cells was performed in altered regions identified by MRI (anterior cingulate and somatosensory cortices, striatum, and hippocampus). Subtle deviations in neurodevelopmental trajectory and subthreshold anxiety-like behaviours were observed in mice exposed to both risk factors. Sex-dependent effects were observed in patterns of shared brain-behaviour covariation, indicative of potential sex differences in response to MIA and THC. Density of CB1 and CB2 receptor positive cells was significantly decreased in all mice exposed to MIA, THC, or both. These findings suggest that there may be a cumulative effect of risk factor exposure on gross neuroanatomical development, and that the endocannabinoid system may be sensitive to both prenatal MIA, adolescent THC, or the combination.

Chronic Δ9-tetrahydrocannabinol impact on plasticity, and differential activation requirement for CB1-dependent long-term depression in ventral tegmental area GABA neurons in adult versus young mice

The ventral tegmental area (VTA) mediates incentive salience and reward prediction error through dopamine (DA) neurons that are regulated by local VTA GABA neurons. In young mice, VTA GABA cells exhibit a form of synaptic plasticity known as long-term depression (LTD) that is dependent on cannabinoid 1 (CB1) receptors preceded by metabotropic glutamate receptor 5 (mGluR5) signaling to induce endocannabinoid production. This LTD was eliminated following chronic (7-10 consecutive days) exposure to the marijuana derived cannabinoid Δ9 -tetrahydrocannabinol (THC). We now examine the mechanism behind THC-induced elimination of LTD in adolescents as well as plasticity induction ability in adult versus young male and female mice using whole-cell electrophysiology experiments of VTA GABA cells. Chronic THC injections in adolescents resulted in a loss of CB1 agonist-mediated depression, illustrating chronic THC likely desensitizes or removes synaptic CB1. We noted that seven days withdrawal from chronic THC restored LTD and CB1 agonist-induced depression, suggesting reversibility of THC-induced changes. Adult mice continue to express functional mGluR5 and CB1, but require a doubling of the synaptic stimulation compared to young mice to induce LTD, suggesting a quantitative difference in CB1-dependent plasticity between young and adult mice. One potential rationale for this difference is changes in AMPA and NMDA glutamate receptors. Indeed, AMPA/NMDA ratios were increased in in adults compared to young mice. Lastly, we performed quantitative reverse-transcription PCR and identified that CB1, DAGLα, and GluA1 levels increased following chronic THC exposure. Collectively, our data demonstrate the first age-dependent GABA neuron plasticity in the VTA, which could have implications for decreased THC dependence capacity in adults, as well as the mechanism behind chronic THC-induced synaptic alterations in young mice.

Daily THC and withdrawal increase dopamine D1-D2 receptor heteromer to mediate anhedonia and anxiogenic-like behavior through a dynorphin and kappa opioid receptor mechanism

Background

Frequent cannabis use is associated with a higher risk of developing cannabis use disorder and other adverse consequences. However, rodent models studying the underlying mechanisms of the reinforcing and withdrawal effects of the primary constituent of cannabis, Δ⁹-tetrahydrocannabinol (THC), have been limited.

Methods

This study investigated the effects of daily THC (1 mg/kg, intraperitoneal, 9 days) and spontaneous withdrawal (7 days) on hedonic and aversion-like behaviors in male rats. In parallel, underlying neuroadaptive changes in dopaminergic, opioidergic, and cannabinoid signaling in the nucleus accumbens were evaluated, along with a candidate peptide designed to reverse altered signaling.

Results

Chronic THC administration induced anhedonic- and anxiogenic-like behaviors not attributable to altered locomotor activity. These effects persisted after drug cessation. In the nucleus accumbens, THC treatment and withdrawal catalyzed increased cannabinoid CB₁ receptor activity without modifying receptor expression. Dopamine D₁-D₂ receptor heteromer expression rose steeply with THC, accompanied by increased calcium-linked signaling, activation of BDNF/TrkB (brain-derived neurotrophic factor/tropomyosin receptor kinase B) pathway, dynorphin expression, and kappa opioid receptor signaling. Disruption of the D₁-D₂ heteromer by an interfering peptide during withdrawal reversed the anxiogenic-like and anhedonic-like behaviors as well as the neurochemical changes.

Conclusions

Chronic THC increases nucleus accumbens dopamine D₁-D₂ receptor heteromer expression and function, which results in increased dynorphin expression and kappa opioid receptor activation. These changes plausibly reduce dopamine release to trigger anxiogenic- and anhedonic-like behaviors after daily THC administration that persist for at least 7 days after drug cessation. These findings conceivably provide a therapeutic strategy to alleviate negative symptoms associated with cannabis use and withdrawal.

Molecular Alterations of the Endocannabinoid System in Psychiatric Disorders

The therapeutic benefits of the current medications for patients with psychiatric disorders contrast with a great variety of adverse effects. The endocannabinoid system (ECS) components have gained high interest as potential new targets for treating psychiatry diseases because of their neuromodulator role, which is essential to understanding the regulation of many brain functions. This article reviewed the molecular alterations in ECS occurring in different psychiatric conditions. The methods used to identify alterations in the ECS were also described. We used a translational approach. The animal models reproducing some behavioral and/or neurochemical aspects of psychiatric disorders and the molecular alterations in clinical studies in post-mortem brain tissue or peripheral tissues were analyzed. This article reviewed the most relevant ECS changes in prevalent psychiatric diseases such as mood disorders, schizophrenia, autism, attentional deficit, eating disorders (ED), and addiction. The review concludes that clinical research studies are urgently needed for two different purposes: (1) To identify alterations of the ECS components potentially useful as new biomarkers relating to a specific disease or condition, and (2) to design new therapeutic targets based on the specific alterations found to improve the pharmacological treatment in psychiatry.

Phytocannabinoids - An Overview of the Analytical Methodologies for Detection and Quantification of Therapeutically and Recreationally Relevant Cannabis Compounds

The legalization of the cultivation of low Δ9-tetrahydrocannabinol (Δ9-THC) and high cannabidiol (CBD) Cannabis Sativa plants is gaining momentum around the world due to increasing demand for CBD-containing products. In many countries where CBD oils, extracts and CBD-infused foods and beverages are being sold in health shops and supermarkets, appropriate testing of these products is a legal requirement. Normally this involves determining the total Δ9-THC and CBD and their precursor tetrahydrocannabinolic acids (THCA) and cannabidiolic acid (CBDA). As our knowledge of the other relevant cannabinoids expands, it is likely so too will the demand for them as additives in many consumer products ensuring a necessity for quantification methods and protocols for their identification. This paper discusses therapeutically relevant cannabinoids found in Cannabis plant, the applicability and efficiency of existing extraction and analytical techniques as well as the legal requirements for these analyses.

Cannabis use, abuse, and withdrawal: Cannabinergic mechanisms, clinical, and preclinical findings

Cannabis sativa is the most widely used illicit drug in the world. Its main psychoactive component is delta‐9‐tetrahydrocannabinol (THC), one of over 100 phytocannabinoid compounds produced by the cannabis plant. THC is the primary compound that drives cannabis abuse potential and is also used and prescribed medically for therapeutic qualities. Despite its therapeutic potential, a significant subpopulation of frequent cannabis or THC users will develop a drug use syndrome termed cannabis use disorder. Individuals suffering from cannabis use disorder exhibit many of the hallmarks of classical addictions including cravings, tolerance, and withdrawal symptoms. Currently, there are no efficacious treatments for cannabis use disorder or withdrawal symptoms. This makes both clinical and preclinical research on the neurobiological mechanisms of these syndromes ever more pertinent. Indeed, basic research using animal models has provided valuable evidence of the neural molecular and cellular actions of cannabis that mediate its behavioral effects. One of the main components being central action on the cannabinoid type‐one receptor and downstream intracellular signaling related to the endogenous cannabinoid system. Back‐translational studies have provided insight linking preclinical basic and behavioral biology research to better understand symptoms observed at the clinical level. This narrative review aims to summarize major research elucidating the molecular, cellular, and behavioral manifestations of cannabis/THC use that play a role in cannabis use disorder and withdrawal.

Fatty acid amide hydrolase is lower in young cannabis users

We have recently shown that levels of fatty acid amide hydrolase (FAAH), the enzyme that metabolizes the endocannabinoid anandamide, are lower in the brains of adult cannabis users (CUs) (34 ± 11 years of age), tested during early abstinence. Here, we examine replication of the lower FAAH levels in a separate, younger cohort (23 ± 5 years of age). Eighteen healthy volunteers (HVs) and fourteen CUs underwent a positron emission tomography scan using the FAAH radioligand [¹¹ C]CURB. Regional [¹¹ C]CURB binding was calculated using an irreversible two-tissue compartment model with a metabolite-corrected arterial plasma input function. The FAAH C385A genetic polymorphism (rs324420) was included as a covariate. All CUs underwent a urine screen to confirm recent cannabis use and had serum cannabinoids measured. One CU screened negative for cannabinoids via serum and was removed from analysis. All HVs reported less than five lifetime cannabis exposures more than a month prior to study initiation. There was a significant effect of group (F_1,26 = 4.31; P = .048) when two A/A (rs324420) HVs were removed from analysis to match the genotype of the CU group (n = 16 HVs, n = 13 CUs). Overall, [¹¹ C]CURB λk₃ was 12% lower in CU compared with HV. Exploratory correlations showed that lower brain [¹¹ C]CURB binding was related to greater use of cannabis throughout the past year. We confirmed our previous report and extended these findings by detecting lower [¹¹ C]CURB binding in a younger cohort with less cumulative cannabis exposure.

The role of cannabinoid 1 receptor in the nucleus accumbens on tramadol induced conditioning and reinstatement

AIMS

Previous investigations demonstrated that tramadol, as a painkiller, similar to morphine induces tolerance and dependence. Furthermore, the cannabinoid receptor 1 (CB1R) located in the nucleus accumbens (NAc) plays a critical role in morphine-induced conditioning. Therefore, the main objective of this study was to evaluate the role of NAc CB1R in tramadol induced conditioning and reinstatement.

MAIN METHODS

In the present experiment, the effect of NAc CB1 receptors on tramadol induced conditioning was tested by microinjecting of arachidonylcyclopropylamide (ACPA, CB1R agonist) and AM 251 (CB1R inverse agonist) in the NAc during tramadol-induced conditioning in the adult male Wistar rats. In addition, the role of NAc CB1R in the reinstatement was also evaluated by injecting ACPA and AM 251 after a 10-days extinction period.

KEY FINDINGS

The obtained data revealed that the administration of tramadol (1,2, and 4 mg/kg, ip) dose-dependently produced conditioned place preference (CPP). Moreover, intra-NAc administration of ACPA (0.25, 0.5, and 1 μg/rat) dose-dependently induced conditioning, while the administration of AM-251 (30, 60, and 120 ng/rat) induced a significant aversion. In addition, the administration of a non-effective dose of AM251 during tramadol conditioning inhibited conditioning induced by tramadol. On the other hand, the administration of ACPA after extinction induced a significant reinstatement. Notably, the locomotor activity did not change among groups.

SIGNIFICANCE

Previous studies have shown that tramadol-induced CPP occurs through μ-opioid receptors. The data obtained in the current study indicated that CB1R located in the NAc is involved in mediating conditioning induced by tramadol. Besides, CB1R also plays a vital role in the reinstatement of tramadol-conditioned animals. It might be due to the effect of opioids on enhancing the level of CB1R.

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.

Cannabinoids, Endocannabinoids and Sleep

Sleep is a vital function of the nervous system that contributes to brain and bodily homeostasis, energy levels, cognitive ability, and other key functions of a variety of organisms. Dysfunctional sleep induces neural problems and is a key part of almost all human psychiatric disorders including substance abuse disorders. The hypnotic effects of cannabis have long been known and there is increasing use of phytocannabinoids and other formulations as sleep aids. Thus, it is crucial to gain a better understanding of the neurobiological basis of cannabis drug effects on sleep, as well as the role of the endogenous cannabinoid system in sleep physiology. In this review article, we summarize the current state of knowledge concerning sleep-related endogenous cannabinoid function derived from research on humans and rodent models. We also review information on acute and chronic cannabinoid drug effects on sleep in these organisms, and molecular mechanisms that may contribute to these effects. We point out the potential benefits of acute cannabinoids for sleep improvement, but also the potential sleep-disruptive effects of withdrawal following chronic cannabinoid drug use. Prescriptions for future research in this burgeoning field are also provided.

Cannabinoid Hyperemesis Syndrome: A Review of Potential Mechanisms

Introduction: Cannabinoids have long been known for their ability to treat nausea and vomiting. Recent reports, however, have highlighted the paradoxical proemetic effects of cannabinoids. Cannabinoid hyperemesis syndrome (CHS) is characterized by cyclical episodes of nausea and vomiting, accompanied by abdominal pain following prolonged, high-dose cannabis use, which is alleviated by hot baths and showers. Little is known about the cause of this syndrome. Discussion: Cannabinoids produce a biphasic effect on nausea and vomiting, with low doses having an antiemetic effect and high doses producing emesis. Presentation and treatment of CHS are similar to cyclical vomiting syndrome as well as chemotherapy-related anticipatory nausea and vomiting, suggesting that these phenomena may share mechanisms. The prevalence of CHS is not known because of the symptomatic overlap with other disorders and the lack of knowledge of the syndrome by the public and physicians. Treatment with typical antiemetic drugs is ineffective for CHS, but anxiolytic and sedative drugs, along with hot showers, seem to be consistently effective at reducing symptoms. The only known way to permanently end CHS, however, is abstinence from cannabinoids. Case studies and limited pre-clinical data on CHS indicate that prolonged high doses of the main psychotropic compound in cannabis, Δ9-tetrahydrocannabinol (THC), result in changes to the endocannabinoid system by acting on the cannabinoid 1 (CB1) receptor. These endocannabinoid system changes can dysregulate stress and anxiety responses, thermoregulation, the transient receptor potential vanilloid system, and several neurotransmitters systems, and are thus potential candidates for mediating the pathophysiology of CHS. Conclusions: Excessive cannabinoid administration disrupts the normal functioning of the endocannabinoid system, which may cause CHS. More clinical and pre-clinical research is needed to fully understand the underlying pathophysiology of this disorder and the negative consequences of prolonged high-dose cannabis use.

Investigating the cumulative effects of Δ9-tetrahydrocannabinol and repetitive mild traumatic brain injury on adolescent rats

The prevalence of mild traumatic brain injury is highest amongst the adolescent population and can lead to complications including neuroinflammation and excitotoxicity. Also pervasive in adolescents is recreational cannabis use. Δ9-Tetrahydrocannabinol, the main psychoactive component of cannabis, is known to have anti-inflammatory properties and serves as a neuroprotective agent against excitotoxicity. Thus, we investigated the effects of Δ9-tetrahydrocannabinol on recovery when administered either prior to or following repeated mild brain injuries. Male and female Sprague-Dawley rats were randomly assigned to receive Δ9-tetrahydrocannabinol or vehicle either prior to or following the repeated injuries. Rats were then tested on a behavioural test battery designed to measure post-concussive symptomology. The hippocampus, nucleus accumbens and prefrontal cortex were extracted from all animals to examine mRNA expression changes (Bdnf, Cnr1, Comt, GR, Iba-1 and Vegf-2R). We hypothesized that, in both experiments, Δ9-tetrahydrocannabinol administration would provide neuroprotection against mild injury outcomes and confer therapeutic benefit. Δ9-Tetrahydrocannabinol administration following repeated mild traumatic brain injury was beneficial to three of the six behavioural outcomes affected by injury (reducing anxiety and depressive-like behaviours while also mitigating injury-induced deficits in short-term working memory). Δ9-Tetrahydrocannabinol administration following injury also showed beneficial effects on the expression of Cnr1, Comt and Vegf-2R in the hippocampus, nucleus accumbens and prefrontal cortex. There were no notable benefits of Δ9-tetrahydrocannabinol when administered prior to injury, suggesting that Δ9-tetrahydrocannabinol may have potential therapeutic benefit on post-concussive symptomology when administered post-injury, but not pre-injury.

The cannabinoid agonist WIN-2 affects acquisition but not consolidation of a spatial information in training and retraining processes: Relation with transcriptional regulation of the endocannabinoid system?

The endocannabinoid system is capable of modulating multiple physiological brain functions including learning and memory. Moreover, there is evidence that the processes of acquisition and consolidation have distinct biological basis. We used the cannabinoid agonist WIN 55,212-2 (WIN-2) to investigate whether chronic CB1 activation affects acquisition and consolidation differently by evaluating gene expression in the hippocampus (HIP) and prefrontal cortex (PFC). Swiss mice were treated with WIN-2 (2 mg/kg) and submitted to the Morris water maze to evaluate different aspects of memory. We observed short-term memory impairment in acquisition of the spatial task while consolidation remained unchanged. In the PFC, animals that received WIN-2 prior to the task exhibited increased expression of the 2-AG synthesis enzyme diacylglycerol lipase and decreased levels of the degradation enzyme monoacylglycerol lipase, while mice that were treated after the task for the evaluation of consolidation exhibited the opposite profile. With respect to genes related to AEA metabolism, no correlation between the molecular and behavioral data could be established. In this sense, the cognitive impairment in the acquisition promoted by WIN-2 treatment may be related to a possible increase in the concentration of 2-AG in the PFC. Overall, this study confirms the relevance of the endocannabinoid system in the modulation of cognitive processes. A better understanding of the mechanisms underlying endocannabinoids roles in cognition could provide guidance for the development of treatments to reduce the cognitive deficits caused by drug abuse.

Systemic Blockade of the CB1 Receptor Augments Hippocampal Gene Expression Involved in Synaptic Plasticity but Perturbs Hippocampus-Dependent Learning Task

Chronic and acute agonism as well as acute antagonism of CB₁ receptors reveal modulation of learning and memory during stable performance of a delayed-nonmatch-to-sample (DNMS) memory task. However, it remains unclear how chronic blockade of the CB₁ receptor alters acquisition of the behavioral task. We examined the effects of chronic rimonabant exposure during DNMS task acquisition to determine if blockade of the CB₁ receptor with the antagonist rimonabant enhanced acquisition of operant task. Long-Evans rats, trained in the DNMS task before imposition of the trial delay, were surgically implanted with osmotic mini pumps to administer rimonabant (1.0 mg/kg/day) or vehicle (dimethyl sulfoxide/Tween-80/Saline). Following surgical recovery, DNMS training was resumed with the imposition of gradually longer delays (1-30 sec). The number of days required to achieve stable performance with either increasing length of delay or reversal of task contingency was compared between vehicle and rimonabant-treated rats. Following the completion of DNMS training, animals were euthanized, and both hippocampi were harvested for gene expression assay analysis. Rimonabant treatment animals required more time to achieve stable DNMS performance than vehicle-treated controls. Quantitative real-time polymerase chain reaction analysis revealed that the expressions of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor subunit, brain-derived neurotrophic factor, and synapsin 1 (Syn1) were significantly increased. These results are consistent with rimonabant increasing mRNAs for proteins associated with hippocampal synapse remodeling, but that those alterations did not necessarily accelerate the acquisition of an operant behavioral task that required learning new contingencies.

Long lasting effects of chronic WIN55,212-2 treatment on mesostriatal dopaminergic and cannabinoid systems in the rat brain

Cannabinoid administration modulates dopamine transmission via an indirect, multisynaptic mechanism that includes the activation of cannabinoid type-1 receptor (CB1R). The present study evaluated in rodents, the effects of acute and chronic (20 days) WIN55,212-2 administration, a non-selective CB1R agonist, on dopamine uptake and synthesis in the mesolimbic and nigrostriatal dopaminergic pathways and associate them to its effects on the endocannabinoid system. The effect of spontaneous withdrawal, after different abstinence periods (7 days, 20 days), was also assessed. Acute and chronic administration of WIN55,212-2 decreased dopamine transporter (DAT) binding and mRNA levels, as well as tyrosine hydroxylase (TH) mRNA expression in the substantia nigra (SN) and ventral tegmental area (VTA). In the striatum, chronic WIN55,212-2 administration led to decreased protein expression of DAT and TH, whereas no alterations were observed after acute administration, suggesting a diminished dopamine uptake and synthesis after chronic agonist treatment. Furthermore, after chronic agonist treatment, we observed reduced CB1R binding and mRNA levels in SN and striatum, providing evidence for a possible regulatory role of the endocannabinoid system on dopaminergic function. Seven days after WIN55,212-2 cessation, we observed a rebound increase in mRNA, binding and total protein levels of DAT and TH in VTA, SN and striatum proposing the existence of a biphasic expression pattern, which was also observed in CB1R binding levels. Within the 20-day period of abstinence, TH mRNA and protein levels and CB1R binding levels remain increased. The above results indicate that chronic CB1R agonist treatment induces long-lasting control of the mesostriatal dopaminergic activity.

Cannabinoid Receptor 1 Gene by Cannabis Use Interaction on CB1 Receptor Density

Background: Because delta-9-tetrahydrocannabinol (THC), the primary psychoactive ingredient in cannabis, binds to cannabinoid 1 (CB1) receptors, levels of CB1 protein could serve as a potential biomarker for response to THC. To date, available techniques to characterize CB1 expression and function in vivo are limited. In this study, we developed an assay to quantify CB1 in lymphocytes to determine how it relates to cannabis use in 58 daily cannabis users compared with 47 nonusers. Furthermore, we tested whether CB1 levels are associated with mutations in a single nucleotide polymorphism known to regulate CB1 functioning (i.e., rs2023239).

Methods: Total protein concentration was analyzed through the Pierce BCA Protein assay kit. CB1 protein was quantified through CNR1 enzyme-linked immunosorbent assay (ELISA) kit from MyBioSource. CB1 concentration and total protein concentration were quantified and used to calculate a ratio of CB1 to total protein.

Results: Inherent levels of peripheral lymphocyte CB1 were sufficient for quantification through ELISA without protein amplification. We found a group×genotype interaction such that users with the G allele had greater CB1 concentration than users with the A/A genotype, and a trend-level difference between genotypes in nonusers.

Conclusions: This study demonstrates a minimally invasive technique of CB1 quantification that holds promise for the use of CB1 protein concentration, along with rs2023239 genotype, as a potential biomarker for susceptibility to cannabis use. These results suggest a gene (rs2023239 G)×environment (cannabis use) effect on CB1 density.

THC Treatment Alters Glutamate Receptor Gene Expression in Human Stem Cell-Derived Neurons

Given the cognitive and behavioral effects following in utero Δ9-tetrahydrocannabinol (THC) exposure that have been reported in humans and rodents, it is critical to understand the precise consequences of THC on developing human neurons. Here, we utilize excitatory neurons derived from human-induced pluripotent stem cells (hiPSCs), and report that in vitro THC exposure reduced expression of glutamate receptor subunit genes (GRIA1, GRIA2, GRIN2A, and GRIN2B). By expanding these studies across hiPSC-derived neurons from individuals with a variety of genotypes, we believe that a hiPSC-based model will facilitate studies of the interaction of THC exposure and the genetic risk factors underlying neuropsychiatric disease vulnerability.

CB1 and CB2 Receptor Pharmacology

The CB1 and CB2 cannabinoid receptors (CB1R, CB2R) are members of the G protein-coupled receptor (GPCR) family that were identified over 20 years ago. CB1Rs and CB2Rs mediate the effects of Δ9-tetrahydrocannabinol (Δ9-THC), the principal psychoactive constituent of marijuana, and subsequently identified endogenous cannabinoids (endocannabinoids) anandamide and 2-arachidonoyl glycerol. CB1Rs and CB2Rs have both similarities and differences in their pharmacology. Both receptors recognize multiple classes of agonist and antagonist compounds and produce an array of distinct downstream effects. Natural polymorphisms and alternative splice variants may also contribute to their pharmacological diversity. As our knowledge of the distinct differences grows, we may be able to target select receptor conformations and their corresponding pharmacological responses. This chapter will discuss their pharmacological characterization, distribution, phylogeny, and signaling pathways. In addition, the effects of extended agonist exposure and how that affects signaling and expression patterns of the receptors are considered.

CB-1R and GLP-1R gene expressions and oxidative stress in the liver of diabetic rats treated with sitagliptin

BACKGROUND

Type 2 diabetes is a major health problem affecting millions of people. Controlled eating and regular physical activity are important for the management of type 2 diabetes. Dipeptidyl peptidase-4 enzyme (DPP-4) inhibitor sitagliptin is a potent agent for the treatment of type-2 diabetes. The aim of this study was to examine the effects of sitagliptin on the liver of rats with streptozotocin (STZ)-induced diabetes, in terms of (i) the expression levels of the cannabinoid 1 receptor (CB-1R) and glucagon-like peptide 1 receptor (GLP-1R), (ii) alterations in the number and localization of these peptides, and (iii) changes in histological and oxidative damage.

METHODS

Thirty-two neonatal (two-day-old) rats, which were divided into four groups, were treated with saline (control), sitagliptin (control; 1.5mg/kg/day for 15 days starting from day 5 of the experimental period), STZ (diabetes; 100mg/kg single dose), STZ+sitagliptin (diabetes+sitagliptin). After 20 days, hepatic tissues were obtained from rats.

RESULTS

The expressions of GLP-1R and CB-1R mRNA increased approximately 1.89- and 2.94-fold, respectively, in the diabetes+sitagliptin group as compared to the diabetic group. Additionally the number of GLP-1R immunopositive cells decreased and CB-1R immunopositive cells increased in comparison to the diabetic group; however, this was not statistically significant. Glutathione levels increased, but malondialdehyde and protein carbonyl levels decreased in the diabetes+sitagliptin group more than the diabetic group.

CONCLUSION

Our findings indicate that sitagliptin treatment regulates GLP-1R and CB-1R gene expressions, which are associated with appetite regulation in diabetic rat, and may decrease oxidative stress and liver tissue damage.

Mice Expressing a "Hyper-Sensitive" Form of the Cannabinoid Receptor 1 (CB1) Are Neither Obese Nor Diabetic

Multiple lines of evidence implicate the endocannabinoid signaling system in the modulation of metabolic disease. Genetic or pharmacological inactivation of CB1 in rodents leads to reduced body weight, resistance to diet-induced obesity, decreased intake of highly palatable food, and increased energy expenditure. Cannabinoid agonists stimulate feeding in rodents and increased levels of endocannabinoids can disrupt lipid metabolism. Therefore, the hypothesis that sustained endocannabinoid signaling can lead to obesity and diabetes was examined in this study using S426A/S430A mutant mice expressing a desensitization-resistant CB1 receptor. These mice display exaggerated and prolonged responses to acute administration of phytocannabinoids, synthetic cannabinoids, and endocannabinoids. As a consequence these mice represent a novel model for determining the effect of enhanced endocannabinoid signaling on metabolic disease. S426A/S430A mutants consumed equivalent amounts of both high fat (45%) and low fat (10%) chow control diet compared to wild-type littermate controls. S426A/S430A mutants and wild-type mice fed either high or low fat control diet displayed similar fasting blood glucose levels and normal glucose clearance following a 2 g/kg glucose challenge. Furthermore, S426A/S430A mutants and wild-type mice consumed similar amounts of chow following an overnight fast. While both THC and JZL195 significantly increased food intake two hours after injection, this increase was similar between the S426A/S430A mutant and wildtype control mice Our results indicate that S426A/S430A mutant mice expressing the desensitization-resistant form of CB1 do not exhibit differences in body weight, food intake, glucose homeostasis, or re-feeding following a fast.

Broad impact of deleting endogenous cannabinoid hydrolyzing enzymes and the CB1 cannabinoid receptor on the endogenous cannabinoid-related lipidome in eight regions of the mouse brain

BACKGROUND AND PURPOSE

The enzymes fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MAGL) hydrolyze endogenous cannabinoids (eCBs), N-arachidonoyl ethanolamine (AEA) and 2-arachidonoyl glycerol (2-AG), respectively. These enzymes also metabolize eCB analogs such as lipoamines and 2-acyl glycerols, most of which are not ligands at CB1. To test the hypothesis that deleting eCB hydrolyzing enzymes and CB1 shifts lipid metabolism more broadly and impacts more families of eCB structural analogs, targeted lipidomics analyses were performed on FAAH KO, MAGL KO, and CB1 KO mice and compared to WT controls in 8 brain regions.

EXPERIMENTAL APPROACH

Methanolic extracts of discrete brain regions (brainstem, cerebellum, cortex, hippocampus, hypothalamus, midbrain, striatum and thalamus) were partially purified on C-18 solid-phase extraction columns. Over 70 lipids per sample were then analyzed with HPLC/MS/MS.

KEY RESULTS

AEA and 2-AG were unaffected throughout the brain in CB1 KO mice; however, there was an increase in the arachidonic acid (AA) metabolite, PGE2 in the majority of brain areas. By contrast, PGE2 and AA levels were significantly reduced throughout the brain in the MAGL KO corresponding to significant increases in 2-AG. No changes in AA or PGE2 were seen throughout in the FAAH KO brain, despite significant increases in AEA, suggesting AA liberated by FAAH does not contribute to steady state levels of AA or PGE2. Changes in the lipidome were not confined to the AA derivatives and showed regional variation in each of the eCB KO models.

CONCLUSIONS AND IMPLICATIONS

AEA and 2-AG hydrolyzing enzymes and the CB1 receptor link the eCB system to broader lipid signaling networks in contrasting ways, potentially altering neurotransmission and behavior independently of cannabinoid receptor signaling.

Endocannabinoid Signaling Regulates Sleep Stability

The hypnogenic properties of cannabis have been recognized for centuries, but endogenous cannabinoid (endocannabinoid) regulation of vigilance states is poorly characterized. We report findings from a series of experiments in mice measuring sleep with polysomnography after various systemic pharmacological manipulations of the endocannabinoid system. Rapid, unbiased scoring of vigilance states was achieved using an automated algorithm that we devised and validated. Increasing endocannabinoid tone with a selective inhibitor of monoacyglycerol lipase (JZL184) or fatty acid amide hydrolase (AM3506) produced a transient increase in non-rapid eye movement (NREM) sleep due to an augmentation of the length of NREM bouts (NREM stability). Similarly, direct activation of type 1 cannabinoid (CB1) receptors with CP47,497 increased NREM stability, but both CP47,497 and JZL184 had a secondary effect that reduced NREM sleep time and stability. This secondary response to these drugs was similar to the early effect of CB1 blockade with the antagonist/inverse agonist AM281, which fragmented NREM sleep. The magnitude of the effects produced by JZL184 and AM281 were dependent on the time of day this drug was administered. While activation of CB1 resulted in only a slight reduction in gamma power, CB1 blockade had dramatic effects on broadband power in the EEG, particularly at low frequencies. However, CB1 blockade did not significantly reduce the rebound in NREM sleep following total sleep deprivation. These results support the hypothesis that endocannabinoid signaling through CB1 is necessary for NREM stability but it is not necessary for sleep homeostasis.

Cannabinoids and Epilepsy

Cannabis has been used for centuries to treat seizures. Recent anecdotal reports, accumulating animal model data, and mechanistic insights have raised interest in cannabis-based antiepileptic therapies. In this study, we review current understanding of the endocannabinoid system, characterize the pro- and anticonvulsive effects of cannabinoids [e.g., Δ9-tetrahydrocannabinol and cannabidiol (CBD)], and highlight scientific evidence from pre-clinical and clinical trials of cannabinoids in epilepsy. These studies suggest that CBD avoids the psychoactive effects of the endocannabinoid system to provide a well-tolerated, promising therapeutic for the treatment of seizures, while whole-plant cannabis can both contribute to and reduce seizures. Finally, we discuss results from a new multicenter, open-label study using CBD in a population with treatment-resistant epilepsy. In all, we seek to evaluate our current understanding of cannabinoids in epilepsy and guide future basic science and clinical studies.

Hormonal status and age differentially affect tolerance to the disruptive effects of delta-9-tetrahydrocannabinol (Δ(9)-THC) on learning in female rats

The effects of hormone status and age on the development of tolerance to Δ(9)-THC were assessed in sham-operated (intact) or ovariectomized (OVX) female rats that received either intraperitoneal saline or 5.6 mg/kg of Δ(9)-THC daily from postnatal day (PD) 75-180 (early adulthood onward) or PD 35-140 (adolescence onward). During this time, the four groups for each age (i.e., intact/saline, intact/THC, OVX/saline, and OVX/THC) were trained in a learning and performance procedure and dose-effect curves were established for Δ(9)-THC (0.56-56 mg/kg) and the cannabinoid type-1 receptor (CB1R) antagonist rimonabant (0.32-10 mg/kg). Despite the persistence of small rate-decreasing and error-increasing effects in intact and OVX females from both ages during chronic Δ(9)-THC, all of the Δ(9)-THC groups developed tolerance. However, the magnitude of tolerance, as well as the effect of hormone status, varied with the age at which chronic Δ(9)-THC was initiated. There was no evidence of dependence in any of the groups. Hippocampal protein expression of CB1R, AHA1 (a co-chaperone of CB1R) and HSP90β (a molecular chaperone modulated by AHA-1) was affected more by OVX than chronic Δ(9)-THC; striatal protein expression was not consistently affected by either manipulation. Hippocampal brain-derived neurotrophic factor expression varied with age, hormone status, and chronic treatment. Thus, hormonal status differentially affects the development of tolerance to the disruptive effects of delta-9-tetrahydrocannabinol (Δ(9)-THC) on learning and performance behavior in adolescent, but not adult, female rats. These factors and their interactions also differentially affect cannabinoid signaling proteins in the hippocampus and striatum, and ultimately, neural plasticity.

The influence of cannabinoids on learning and memory processes of the dorsal striatum

Extensive evidence indicates that the mammalian endocannabinoid system plays an integral role in learning and memory. Our understanding of how cannabinoids influence memory comes predominantly from studies examining cognitive and emotional memory systems mediated by the hippocampus and amygdala, respectively. However, recent evidence suggests that cannabinoids also affect habit or stimulus-response (S-R) memory mediated by the dorsal striatum. Studies implementing a variety of maze tasks in rats indicate that systemic or intra-dorsolateral striatum infusions of cannabinoid receptor agonists or antagonists impair habit memory. In mice, cannabinoid 1 (CB1) receptor knockdown can enhance or impair habit formation, whereas Δ(9)THC tolerance enhances habit formation. Studies in human cannabis users also suggest an enhancement of S-R/habit memory. A tentative conclusion based on the available data is that acute disruption of the endocannabinoid system with either agonists or antagonists impairs, whereas chronic cannabinoid exposure enhances, dorsal striatum-dependent S-R/habit memory. CB1 receptors are required for multiple forms of striatal synaptic plasticity implicated in memory, including short-term and long-term depression. Interactions with the hippocampus-dependent memory system may also have a role in some of the observed effects of cannabinoids on habit memory. The impairing effect often observed with acute cannabinoid administration argues for cannabinoid-based treatments for human psychopathologies associated with a dysfunctional habit memory system (e.g. post-traumatic stress disorder and drug addiction/relapse). In addition, the enhancing effect of repeated cannabinoid exposure on habit memory suggests a novel neurobehavioral mechanism for marijuana addiction involving the dorsal striatum-dependent memory system.

Seizing an opportunity for the endocannabinoid system

Exogenous cannabinoids can limit seizures and neurodegeneration, and their actions are largely mimicked by endogenous cannabinoids (endocannabinoids). Endocannabinoids are mobilized by epileptiform activity and in turn influence this activity by inhibiting synaptic transmission; both excitatory and some inhibitory synapses can be suppressed, leading to potentially complex outcomes. Moreover, the endocannabinoid system is not a fixed entity, and its strength can be enhanced or reduced. Endocannabinoids and their receptors are altered by epileptic seizures in ways that can reduce the efficacy of both exogenous and endogenous cannabinoids in sometimes unexpected ways.

Peripheral and intra-dorsolateral striatum injections of the cannabinoid receptor agonist WIN 55,212-2 impair consolidation of stimulus-response memory

The endocannabinoid system plays a major role in modulating memory. In the present study, we examined whether cannabinoid agonists influence the consolidation of stimulus-response/habit memory, a form of memory dependent upon the dorsolateral striatum (DLS). In Experiment 1, rats were trained in a cued platform water maze task in which animals were released from different start points and in order to escape had to find a cued platform which was moved to various spatial locations across trials. Immediately following training, rats received an i.p. injection of the cannabinoid receptor agonist WIN 55,212-2 (1 or 3mg/kg) or a vehicle solution. In Experiment 2, rats were trained in a forced-response version of the water plus-maze task in which a consistent body-turn response was reinforced across trials. Immediately following training, rats received an i.p. injection of WIN 55,212-2 (3 mg/kg) or vehicle. In Experiment 3, rats were trained in the cued platform task and after training received bilateral intra-DLS WIN 55,212-2 (100 ng/.5 μL or 200 ng/.5 μL) or vehicle. In Experiments 1-3, the higher doses of WIN 55,212-2 were associated with significant memory impairments, relative to vehicle-treated controls. The results indicate that peripheral or intra-DLS administration of a cannabinoid receptor agonist impairs consolidation of DLS-dependent memory. The findings are discussed within the context of previous research encompassing cannabinoids and DLS-dependent learning and memory processes, and the possibility that cannabinoids may be used to treat some habit-like human psychopathologies (e.g. posttraumatic stress disorder) is considered.

Care and feeding of the endocannabinoid system: a systematic review of potential clinical interventions that upregulate the endocannabinoid system

Background

The “classic” endocannabinoid (eCB) system includes the cannabinoid receptors CB₁ and CB₂, the eCB ligands anandamide (AEA) and 2-arachidonoylglycerol (2-AG), and their metabolic enzymes. An emerging literature documents the “eCB deficiency syndrome” as an etiology in migraine, fibromyalgia, irritable bowel syndrome, psychological disorders, and other conditions. We performed a systematic review of clinical interventions that enhance the eCB system—ways to upregulate cannabinoid receptors, increase ligand synthesis, or inhibit ligand degradation.

Methodology/Principal Findings

We searched PubMed for clinical trials, observational studies, and preclinical research. Data synthesis was qualitative. Exclusion criteria limited the results to 184 in vitro studies, 102 in vivo animal studies, and 36 human studies. Evidence indicates that several classes of pharmaceuticals upregulate the eCB system, including analgesics (acetaminophen, non-steroidal anti-inflammatory drugs, opioids, glucocorticoids), antidepressants, antipsychotics, anxiolytics, and anticonvulsants. Clinical interventions characterized as “complementary and alternative medicine” also upregulate the eCB system: massage and manipulation, acupuncture, dietary supplements, and herbal medicines. Lifestyle modification (diet, weight control, exercise, and the use of psychoactive substances—alcohol, tobacco, coffee, cannabis) also modulate the eCB system.

Conclusions/Significance

Few clinical trials have assessed interventions that upregulate the eCB system. Many preclinical studies point to other potential approaches; human trials are needed to explore these promising interventions.

Does the neuroprotective role of anandamide display diurnal variations?

The endocannabinoid system is a component of the neuroprotective mechanisms that an organism displays after traumatic brain injury (TBI). A diurnal variation in several components of this system has been reported. This variation may influence the recovery and survival rate after TBI. We have previously reported that the recovery and survival rate of rats is higher if TBI occurs at 1:00 than at 13:00. This could be explained by a diurnal variation of the endocannabinoid system. Here, we describe the effects of anandamide administration in rats prior to the induction of TBI at two different times of the day: 1:00 and 13:00. We found that anandamide reduced the neurological damage at both times. Nevertheless, its effects on bleeding, survival, food intake, and body weight were dependent on the time of TBI. In addition, we analyzed the diurnal variation of the expression of the cannabinoid receptors CB1R and CB2R in the cerebral cortex of both control rats and rats subjected to TBI. We found that CB1R protein was expressed more during the day, whereas its mRNA level was higher during the night. We did not find a diurnal variation for the CB2R. In addition, we also found that TBI increased CB1R and CB2R in the contralateral hemisphere and disrupted the CB1R diurnal cycle.

Microglial activation underlies cerebellar deficits produced by repeated cannabis exposure

Chronic cannabis exposure can lead to cerebellar dysfunction in humans, but the neurobiological mechanisms involved remain incompletely understood. Here, we found that in mice, subchronic administration of the psychoactive component of cannabis, delta9-tetrahydrocannabinol (THC), activated cerebellar microglia and increased the expression of neuroinflammatory markers, including IL-1β. This neuroinflammatory phenotype correlated with deficits in cerebellar conditioned learning and fine motor coordination. The neuroinflammatory phenotype was readily detectable in the cerebellum of mice with global loss of the CB1 cannabinoid receptor (CB1R, Cb1(-/-) mice) and in mice lacking CB1R in the cerebellar parallel fibers, suggesting that CB1R downregulation in the cerebellar molecular layer plays a key role in THC-induced cerebellar deficits. Expression of CB2 cannabinoid receptor (CB2R) and Il1b mRNA was increased under neuroinflammatory conditions in activated CD11b-positive microglial cells. Furthermore, administration of the immunosuppressant minocycline or an inhibitor of IL-1β receptor signaling prevented the deficits in cerebellar function in Cb1(-/-) and THC-withdrawn mice. Our results suggest that cerebellar microglial activation plays a crucial role in the cerebellar deficits induced by repeated cannabis exposure.

The dynamic nature of type 1 cannabinoid receptor (CB(1) ) gene transcription

The type 1 cannabinoid receptor (CB(1) ) is an integral component of the endocannabinoid system that modulates several functions in the CNS and periphery. The majority of our knowledge of the endocannabinoid system involves ligand-receptor binding, mechanisms of signal transduction, and protein-protein interactions. In contrast, comparatively little is known about regulation of CB(1) gene expression. The levels and anatomical distribution of CB(1) mRNA and protein are developmental stage-specific and are dysregulated in several pathological conditions. Moreover, exposure to a variety of drugs, including cannabinoids themselves, alters CB(1) gene expression and mRNA levels. As such, alterations in CB(1) gene expression are likely to affect the optimal response to cannabinoid-based therapies, which are being developed to treat a growing number of conditions. Here, we will examine the regulation of CB(1) mRNA levels and the therapeutic potential inherent in manipulating expression of this gene.

LINKED ARTICLES

This article is part of a themed section on Cannabinoids. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2012.167.issue-8.

Withdrawal from THC during adolescence: sex differences in locomotor activity and anxiety

Research suggests that the use and abuse of marijuana can be especially harmful if it occurs during adolescence, a period of vast developmental changes throughout the brain. Due to the localization of cannabinoid receptors within the limbic system and the established effects of cannabinoids on emotional states and anxiety levels of rats and humans, we studied the sex- and dose-related effects of Δ⁹-tetrahydrocannabinol (THC, the main psychoactive component in marijuana) on behavior and anxiety during spontaneous withdrawal. Male and female Sprague Dawley rats were administered 2, 7.5 or 15 mg/kg THC or vehicle from postnatal day 35-41 (approximating mid-adolescence in humans). Locomotor activity and anxiety-related behaviors were measured during drug administration and abstinence. THC caused significant dose-dependent locomotor depression during drug administration. Locomotor depression initially abated upon drug cessation, but re-emerged by the end of the abstinence period and was greater in female than male rats. We found sensitization to the locomotor-depressing effects of THC in middle- and high-dose rats and the subsequent development of tolerance in high-dose rats. The high dose of THC increased anxiety-like behaviors while the low dose decreased anxiety-like behaviors during drug administration, with females more sensitive to the anxiogenic effects of THC than males. During abstinence, females were again especially sensitive to the anxiogenic effects of THC. This study demonstrates sexually-dimorphic effects of THC on anxiety-related behaviors and locomotor activity during and after THC administration during adolescence. This information may be useful in the development of therapeutic approaches for the treatment of marijuana withdrawal in adolescents.

Corticosterone mediates reciprocal changes in CB 1 and TRPV1 receptors in primary sensory neurons in the chronically stressed rat

BACKGROUND & AIMS

Chronic stress is associated with visceral hyperalgesia in functional gastrointestinal disorders. We investigated whether corticosterone plays a role in chronic psychological stress-induced visceral hyperalgesia.

METHODS

Male rats were subjected to 1-hour water avoidance (WA) stress or subcutaneous corticosterone injection daily for 10 consecutive days in the presence or absence of corticoid-receptor antagonist RU-486 and cannabinoid-receptor agonist WIN55,212-2. The visceromotor response to colorectal distension was measured. Receptor protein levels were measured and whole-cell patch-clamp recordings were used to assess transient receptor potential vanilloid type 1 (TRPV1) currents in L6-S2 dorsal root ganglion (DRG) neurons. Mass spectrometry was used to measure endocannabinoid anandamide content.

RESULTS

Chronic WA stress was associated with visceral hyperalgesia in response to colorectal distension, increased stool output and reciprocal changes in cannabinoid receptor 1 (CB1) (decreased) and TRPV1 (increased) receptor expression and function. Treatment of WA stressed rats with RU-486 prevented these changes. Control rats treated with serial injections of corticosterone in situ showed a significant increase in serum corticosterone associated with visceral hyperalgesia, enhanced anandamide content, increased TRPV1, and decreased CB1 receptor protein levels, which were prevented by co-treatment with RU-486. Exposure of isolated control L6-S2 DRGs in vitro to corticosterone reproduced the changes in CB1 and TRPV1 receptors observed in situ, which was prevented by co-treatment with RU-486 or WIN55,212-2.

CONCLUSIONS

These results support a novel role for corticosterone to modulate CB1 and TRPV1-receptor pathways in L6-S2 DRGs in the chronic WA stressed rat, which contributes to visceral hyperalgesia observed in this model.

Cannabinoid CB1 receptor immunoreactivity in the prefrontal cortex: Comparison of schizophrenia and major depressive disorder

We recently showed that measures of cannabinoid 1 receptor (CB1R) mRNA and protein were significantly reduced in dorsolateral prefrontal cortex (DLPFC) area 9 in schizophrenia subjects relative to matched normal comparison subjects. However, other studies have reported unaltered or higher measures of CB1R levels in schizophrenia. To determine whether these discrepancies reflect differences across brain regions or across subject groups (eg, presence of depression, cannabis exposure, etc), we used immunocytochemical techniques to determine whether lower levels of CB1R immunoreactivity are (1) present in another DLPFC region, area 46, in the same subjects with schizophrenia, (2) present in area 46 in a new cohort of schizophrenia subjects, (3) present in major depressive disorder (MDD) subjects, or (4) attributable to factors other than a diagnosis of schizophrenia, including prior cannabis use. CB1R immunoreactivity levels in area 46 were significantly 19% lower in schizophrenia subjects relative to matched normal comparison subjects, a deficit similar to that observed in area 9 in the same subjects. In a new cohort of subjects, CB1R immunoreactivity levels were significantly 20 and 23% lower in schizophrenia subjects relative to matched comparison and MDD subjects, respectively. The lower levels of CB1R immunoreactivity in schizophrenia subjects were not explained by other factors such as cannabis use, suicide, or pharmacological treatment. In addition, CB1R immunoreactivity levels were not altered in monkeys chronically exposed to haloperidol. Thus, the lower levels of CB1R immunoreactivity may be common in schizophrenia, conserved across DLPFC regions, not present in MDD, and not attributable to other factors, and thus a reflection of the underlying disease process.

Reduced expression of glutamate receptors and phosphorylation of CREB are responsible for in vivo Delta9-THC exposure-impaired hippocampal synaptic plasticity

Chronic use of marijuana impairs synaptic plasticity and cognitive function. However, the molecular mechanisms by which marijuana alters long-term synaptic plasticity are largely unknown. Here, we show that repeated in vivo exposures to Delta9-THC for 7 consecutive days significantly impaired hippocampal long-term potentiation (LTP) of excitatory glutamatergic synaptic transmission. The Delta9-THC exposure-induced decrease in LTP was prevented by pharmacological inhibition or deletion of the cannabinoid 1 receptor (CB1R). To determine the molecular mechanisms underlying Delta9-THC-altered LTP, we targeted expression and function of the glutamate receptors (GluR) and phosphorylation status of cAMP-response element-binding protein (CREB). Chronic in vivo exposure to Delta9-THC produced CB1R-dependent decreases in expression of hippocampal GluR1, NR2A, and NR2B, the ratio of alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA)/NMDA receptor-gated currents, and phosphorylation of CREB. Our results suggest that reduced expression and function of the GluR subunits and phosphorylation of CREB may underlie the impaired long-term synaptic plasticity induced by repeated in vivo exposure to Delta9-THC.

Neurobiological consequences of maternal cannabis on human fetal development and its neuropsychiatric outcome

Despite the high prevalence of marijuana use among pregnant women and adolescents, the impact of cannabis on the developing brain is still not well understood. However, growing evidence supports that the endocannabinoid system plays a major role in CNS patterning in structures relevant for mood, cognition, and reward, such as the mesocorticolimbic system. It is thus clear that exposure to cannabis during early ontogeny is not benign and potential compensatory mechanisms that might be expected to occur during neurodevelopment appear insufficient to eliminate vulnerability to neuropsychiatric disorders in certain individuals. Both human longitudinal cohort studies and animal models strongly emphasize the long-term influence of prenatal cannabinoid exposure on behavior and mental health. This review provides an overview of the endocannabinoid system and examines the neurobiological consequences of cannabis exposure in pregnancy and early life by addressing its impact on the development of neurotransmitters systems relevant to neuropsychiatric disorders and its association with these disorders later in life. It posits that studying in utero cannabis exposure in association with genetic mutations of neural systems that have strong relationships to endocannabinoid function, such as the dopamine, opioid, glutamate, and GABA, might help to identify individuals at risk. Such data could add to existing knowledge to guide public health platform in regard to the use of cannabis and its derivatives during pregnancy.

Role of cannabinoids and endocannabinoids in cerebral ischemia

The human costs of stroke are very large and growing; it is the third largest cause of death in the United States and survivors are often faced with loss of ability to function independently. There is a large need for therapeutic approaches that act to protect neurons from the injury produced by ischemia and reperfusion. The goal of this review is to introduce and discuss the available data that endogenous cannabinoid signaling is altered during ischemia and that it contributes to the consequences of ischemia-induced injury. Overall, the available data suggest that inhibition of CB1 receptor activation together with increased CB2 receptor activation produces beneficial effects.

Reduced cortical cannabinoid 1 receptor messenger RNA and protein expression in schizophrenia

CONTEXT

Cannabis use is associated with both impaired cognitive functions, including working memory, and an increased risk of schizophrenia. Schizophrenia is characterized by impairments in working memory that are associated with reduced gamma-aminobutyric acid (GABA) neurotransmission in the dorsolateral prefrontal cortex. The cannabinoid 1 receptor (CB1R) is highly expressed in the dorsolateral prefrontal cortex, is contained in the axon terminals of a subpopulation of perisomatic-targeting GABA neurons, and, when activated, suppresses the release of GABA.

OBJECTIVE

To determine the potential relationship between CB1R signaling and altered GABA neurotransmission in schizophrenia by evaluating CB1R messenger RNA (mRNA) and protein expression in the dorsolateral prefrontal cortex.

DESIGN

In situ hybridization and immunocytochemistry techniques were used to examine the cortical levels of CB1R mRNA and protein, respectively.

SETTING

Brain specimens were obtained from autopsies conducted at the Allegheny County Medical Examiner's Office, Pittsburgh, Pennsylvania.

PARTICIPANTS

Postmortem brain specimens from 23 pairs of subjects with schizophrenia and age-, sex-, and postmortem interval-matched comparison subjects, as well as brain specimens from 18 macaque monkeys with long-term exposure to haloperidol, olanzapine, or placebo.

MAIN OUTCOME MEASURES

Optical density measures of CB1R mRNA expression and protein levels and correlations with previously reported glutamic acid decarboxylase 67 and cholecystokinin mRNA measures.

RESULTS

Levels of CB1R mRNA were significantly lower by 14.8% in the subjects with schizophrenia. Similarly, CB1R protein levels, assessed by radioimmunocytochemistry and standard immunocytochemistry, were significantly decreased by 11.6% and 13.9%, respectively. Group differences in CB1R mRNA levels were significantly correlated with those in glutamic acid decarboxylase 67 and cholecystokinin mRNA levels. Expression of CB1R mRNA was not changed in antipsychotic-exposed monkeys, and neither CB1R mRNA levels nor protein levels were affected by potential confounding factors in the subjects with schizophrenia.

CONCLUSIONS

This combination of findings suggests the testable hypothesis that reduced CB1R mRNA and protein levels in schizophrenia represent a compensatory mechanism to increase GABA transmission from perisomatic-targeting cholecystokinin interneurons with impaired GABA synthesis.

Transcriptomic and proteomic analyses of mouse cerebellum reveals alterations in RasGRF1 expression following in vivo chronic treatment with delta 9-tetrahydrocannabinol

We have applied transcriptomic and proteomic techniques to identify changes in the RNA and the protein levels in the mouse cerebellum after chronic treatment with Delta(9)-tetrahydrocannabinol (THC). Among approximately 14,000 transcripts in a mouse cDNA microarray library, we found 11 genes with altered expression. RasGRF1, a neuron-specific Ras guanine nucleotide exchange factor, showed a reduction both at the RNA and protein levels with a specific decrease of the protein pool associated to cell membranes. In addition, proteomic analysis on cerebellum obtained from chronically THC-treated mice detected quantitative changes of additional 27 spots, mostly in the membranous fraction. We found enrichment of alpha (Galphao, Galphaq) and beta subunits (beta4/beta2 and beta5) of guanine nucleotide-binding proteins and of two calcium-binding proteins, calretinin and hippocalcin-like protein-1. In addition, we also detected a significant increase in the membrane fraction of proteins involved in exo-endocytosis such as septins, dynamin-1, and vesicle protein sorting 29. By western blotting, we confirmed increased membrane localization of calretinin and of dynamin-1 isoforms with higher isoelectric point, indicative for an underphosphorylated state of the molecule. In conclusion, our results indicate that chronic THC modulates the expression and subcellular localization of proteins implicated in Ras signaling, calcium-buffering potential, and trafficking.

Endocannabinoid regulation of relapse mechanisms

Addiction involves a complex neuropharmacologic behavioural cycle, in which positive reinforcement exerted by the drug and the negative state of withdrawal drive the user to extremes to obtain the drug. Comprehensive studies have established that relapse is the most common outcome of recovery programs treating addictive behaviours. Several types of anticraving medication are available nowadays, such as naltrexone for the treatment of alcoholism, bupropion for nicotine, methadone or buprenorphine for heroin. This review focuses on recent behavioural data providing a rationale for an endocannabinoid mechanism underlying reinstatement of compulsive drug seeking. Studies supporting the contention that reinstatement of extinguished drug self-administration behaviour may be generated by cannabinoid CB1 receptor agonists and attenuated, if not blocked, by CB1 receptor antagonists, are here reviewed. In support to these findings, conditioned place preference studies substantiate the involvement of the endocannabinoid system in recidivism mechanisms by demonstrating that motivation to relapse can be triggered by CB1 receptor activation while blockade of such receptors may prevent reinstatement of place conditioning induced by either drug primings or drug-associated cues. Finally, biochemical studies evaluating changes in endocannabinoid levels, CB1 receptor density and CB1 mRNA expression during re-exposure to drug following extinction are also examined. Taken together, the evidence available has important implications in the understanding and treatment of relapsing episodes in patients undergoing detoxification.

Expression of Cannabinoid CB1 Receptors in Models of Diabetic Neuropathy

A clearer understanding of the mechanisms underlying the development and progression of diabetic neuropathy is likely to indicate new directions for the treatment of this complication of diabetes. In the present study we investigated the expression of cannabinoid CB(1) receptors in models of diabetic neuropathy. PC12 cells were differentiated into a neuronal phenotype with nerve growth factor (NGF) (50 ng/ml) in varying concentrations of glucose (5.5-50 mM). CB(1) receptor expression was studied at the mRNA level by reverse transcriptase-polymerase chain reaction (RT-PCR) and at the protein level via immunohistochemical and Western blot analysis. CB(1) expression was also compared in dorsal root ganglia (DRG) removed from streptozotocin-induced diabetic rats versus control animals. Total neurite length induced by NGF was reduced in cells cultured in 20 to 50 mM glucose at day 6 (P < 0.01 versus 5.5 mM; n = 6). Cell viability assays conducted in parallel on day 6 confirmed that the total cell numbers were not significantly different among the various glucose concentrations (P = 0.86; n = 12). RT-PCR, immunohistochemical, and Western blot analysis all revealed down-regulation of the CB(1) receptor in cells treated with high glucose (P < 0.05; n = 4-5 for each), and in DRG removed from diabetic rats compared with controls (P < 0.01; n = 5 for immunohistochemistry, and n = 3 for Western blot). These results suggest that high glucose concentrations are associated with decreased expression of CB(1) receptors in nerve cells. Given the neuroprotective effect of cannabinoids, a decline in CB(1) receptor expression may contribute to the neurodegenerative process observed in diabetes.

Chronic use of marijuana decreases cannabinoid receptor binding and mRNA expression in the human brain

Chronic exposure to Cannabis sativa (marijuana) produced a significant down-regulation of cannabinoid receptor in the postmortem human brain. The significant decrease in maximal binding capacity was not accompanied by changes in the affinity constant. [3H]SR141716A binding was reduced in the caudate nucleus, putamen and in the accumbens nucleus. A significant decrease of binding sites was seen in the globus pallidus. Also in the ventral tegmental area and substantia nigra pars reticulata quantitative analysis of the density of receptors shows a significant reduction in [3H]SR141716A binding. In Cannabis sativa user brains, compared with normal brains [3H]SR141716A binding was reduced only in the hippocampus. The density of cannabinoid receptor 1 mRNA-positive neurons was significantly lower in Cannabis sativa users than in control brains for the caudate nucleus, putamen, accumbens nucleus and hippocampal region (CA1-CA4, areas of Ammon's horn). No hybridization was seen in the mesencephalon and globus pallidus.

Transcriptional profiling of depolarization-dependent phenotypic alterations in primary cultures of developing granule neurons

Rat cerebellar granule neurons cultured in medium supplemented with elevated KCl are extensively used as a model to examine the coupling between neural activity and Ca(2+)-dependent gene expression. Elevated (25 mM) KCl is believed to mimic endogenous neural activity because it promotes depolarization and Ca(+2)-dependent survival and some aspects of maturation. By comparison, at least half of the granule neurons grown in standard medium containing 5 mM KCl undergo apoptosis beginning approximately 4 days in vitro. However, accumulating evidence suggests that chronic depolarization induces phenotypic abnormalities whereas growth in chemically defined medium containing 5 mM KCl more closely resembles the constitutive phenotype. To examine this, oligonucleotide microarrays and RT-PCR of selected mRNAs were used to compare transcription profiles of cultures grown in 5 mM and 25 mM KCl. In some cases, N-methyl-D-aspartate (NMDA) which, like elevated KCl, promotes long-term survival was also tested. Robust changes in several gene groups were observed and indicated that growth in elevated KCl: induces expression of mRNAs that are not normally observed; represses expression of mRNAs that should be present; maintains expression of mRNAs that are markers of immature neurons. Supplementation of the growth medium with NMDA instead of elevated KCl produces similar abnormalities. Altogether, these data indicate that growth in 5 mM KCl more closely mimics survival and maturation of granule neurons in vivo and should therefore be adopted in future studies.

Prolonged recovery rate of CB1 receptor adaptation after cessation of long-term cannabinoid administration

Long-term cannabinoid administration produces region-dependent CB1 receptor desensitization and down-regulation. This study examined the time course for normalization of CB1 receptors and G-protein activation using 3H-labeled N-(piperidin-1-yl)-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboximide hydrochloride (SR141716A) and guanosine 5'-O-(3-[35S]thio)triphosphate ([35S]GTPgammaS binding), respectively, in hippocampus and striatum/globus pallidus (GP). Mice were treated with escalating doses of Delta9-tetrahydrocannabinol (Delta9-THC) or R+-[2,3-dihydro-5-methyl-3-[(morpholinyl)methyl]pyrrolo-[1,2,3-de]-1,4-benzoxazinyl]-(1-naphthalenyl)methanone mesylate (WIN55,212-2) for 15 days, and tissue was collected 1, 3, 7, or 14 days after final injection. [3H]SR141716A and WIN55,212-2-stimulated [35S]GTPgammaS binding were decreased in both regions 1 day after treatment. WIN55,212-2-stimulated G-protein activation in striatum/GP returned to control level at 3 days after cessation of treatment with either drug but did not return to control level in hippocampus until 14 days. CB1 receptor binding did not recover to control levels until day 7 or 14 after treatment in striatum/GP and hippocampus, respectively. The mechanism of CB1 binding site down-regulation was investigated after long-term Delta9-THC treatment. Analysis of CB1 receptor mRNA in hippocampus and striatum/GP showed that transcriptional regulation could not explain prolonged recovery rates from CB1 receptor down-regulation. In contrast, CB1 receptor protein, as determined by immunoblot analysis, matched the down-regulation and recovery rates of CB1 receptor binding sites relatively closely. These data demonstrate that cannabinoid-induced decreases in CB1 receptor function persist for relatively long time periods after cessation of long-term drug treatment and that CB1 receptor signaling recovers more quickly in striatum/GP than hippocampus. Moreover, down-regulation of CB1 receptor binding sites does not seem to result mainly from transcriptional regulation, suggesting that adaptive regulation of CB1 receptors in brain primarily occurs at the protein level.

Cannabinoid tolerance and dependence

The use of marijuana for recreational and medicinal purposes has resulted in a large prevalence of chronic marijuana users. Consequences of chronic cannabinoid administration include profound behavioral tolerance and withdrawal symptoms upon drug cessation. A marijuana withdrawal syndrome is only recently gaining acceptance as being clinically significant. Similarly, laboratory animals exhibit both tolerance and dependence following chronic administration of cannabinoids. These animal models are being used to evaluate the high degree of plasticity that occurs at the molecular level in various brain regions following chronic cannabinoid exposure. In this review, we describe recent advances that have increased our understanding of the impact of chronic cannabinoid administration on cannabinoid receptors and their signal transduction pathways. Additionally, we discuss several potential pharmacotherapies that have been examined to treat marijuana dependence.

Chronic exposure to Delta9-tetrahydrocannabinol downregulates oxytocin and oxytocin-associated neurophysin in specific brain areas

Cannabinoids are widely abused drugs. Our goal was to identify genes modulated by Delta9-tetrahydrocannabinol (Delta9-THC) treatment. We found that chronic administration of Delta9-THC (1.5 mg/kg/day, i.p.; 7 days) to rats, downregulates the expression of oxytocin-neurophysin (OT-NP) mRNA and of OT and oxytocin-associated NP (NPOT) immunoreactivity in nucleus accumbens (NAc) and ventral tegmental area (VTA), brain areas involved in reward and addiction. Real-time PCR revealed a 60% and 53% reduction of OT-NP mRNA in NAc and VTA, respectively, under chronic treatment, while no changes were observed in NAc after 24 h. Immunohistochemistry showed a large decrease in number of OT and NPOT-stained fibers in NAc (by 59% and 52%, respectively) and VTA (by 50% and 56%, respectively). No changes in cell staining were observed in the paraventricular nucleus and supraoptic nucleus. As OT is known to inhibit development of drug tolerance and attenuate withdrawal symptoms, we suggest that OT downregulation could play a role during the establishment of the chronic effects of Delta9-THC.