Cannabinoid function in learning, memory and plasticity

Cannabis constituents for chronic neuropathic pain; reconciling the clinical and animal evidence

Chronic neuropathic pain is a debilitating pain syndrome caused by damage to the nervous system that is poorly served by current medications. Given these problems, clinical studies have pursued extracts of the plant Cannabis sativa as alternative treatments for this condition. The vast majority of these studies have examined cannabinoids which contain the psychoactive constituent delta-9-tetrahydrocannabinol (THC). While there have been some positive findings, meta-analyses of this clinical work indicates that this effectiveness is limited and hampered by side-effects. This review focuses on how recent preclinical studies have predicted the clinical limitations of THC-containing cannabis extracts, and importantly, point to how they might be improved. This work highlights the importance of targeting channels and receptors other than cannabinoid CB1 receptors which mediate many of the side-effects of cannabis.

The interaction between cannabinoids and long-term synaptic plasticity: A survey on memory formation and underlying mechanisms

Synaptic plasticity, including long-term potentiation (LTP) and long-term depression (LTD), is an essential phenomenon in memory formation as well as maintenance along with many other cognitive functions, such as those needed for coping with external stimuli. Synaptic plasticity consists of gradual changes in the biochemistry and morphology of pre- and postsynaptic neurons, particularly in the hippocampus. Consuming marijuana as a primary source of exocannabinoids immediately impairs attention and working memory-related tasks. Evidence regarding the effects of cannabinoids on LTP and memory is contradictory. While cannabinoids can affect a variety of specific cannabinoid receptors (CBRs) and nonspecific receptors throughout the body and brain, they exert miscellaneous systemic and local cerebral effects. Given the increasing use of cannabis, mainly among the young population, plus its potential adverse long-term effects on learning and memory processes, it could be a future global health challenge. Indeed, the impact of cannabinoids on memory is multifactorial and depends on the dosage, timing, formula, and route of consumption, plus the background complex interaction of the endocannabinoids system with other cerebral networks. Herein, we review how exogenously administrated organic cannabinoids, CBRs agonists or antagonists, and endocannabinoids can affect LTP and synaptic plasticity through various receptors in interaction with other cerebral pathways and primary neurotransmitters.

Does cannabis affect cognitive functioning in patients with schizophrenia?

Introduction

Cannabis use impairs cognitive performance in healthy subjects; several studies have shown improved cognitive outcomes in schizophrenic patients using cannabis. The aim of this study was to evaluate the effects of cannabis use on cognitive function in Moroccan patients with schizophrenia who were cannabis users.

Method

Two groups were recruited in a Moroccan University Psychiatric Centre. Fifty patients diagnosed with schizophrenia according to the DSM-V who were cannabis users (SZ CANN +) and forty-nine patients diagnosed with schizophrenia according to DSM-V who do not use cannabis (SZ CANN-). Cognitive functioning was assessed using the CogState neuropsychological battery.

Results

The results of the study suggest that SZ CANN- patients performed better in the test of psychomotor function, attention and verbal memory. While SZ CANN+ patients performed better in the test of working memory, visual memory and emotional recognition. We found no relationship between SZ CANN+ patients and SZ CANN- patients concerning executive function.

Conclusions

Our results suggest that cannabis use may have different effects on neurocognitive functioning. It is associated with disorders of psychomotor function, attention and verbal memory. So, it is associated with an improvement in working memory, visual memory and emotion recognition.

The Sobering Sting: Oleoyl Serotonin Is a Novel Stephanoconus Snail Venom-Derived Antagonist of Cannabinoid Receptors That Counteracts Learning and Memory Deficits

Cannabinoid receptors (CB1 and CB2) are promising targets for a better understanding of neurological diseases. Nevertheless, only a few ligands of CB have reached clinical application so far. Venoms are considered as interesting sources of novel biologically active compounds. Here, we describe an endocannabinoid-like molecule, oleoyl serotonin (OS), present in the venom of Stephanoconus snails. Using electrophysiological assays, it was shown that OS inhibits CB1 and CB2. Structure-activity relationship studies using a chimeric CB1/2 revealed that the domain encompassing the transmembrane helix V (TMHV)- intracellular loop 3 (ICL3)-TMHVI of the CB2 is critical for the binding and function of OS. We concluded that OS binds to sites of the CB2 that are different from the binding sites of the non-selective CB agonist WIN55,212-2. Behavioral assays in mice showed that OS counteracted learning and memory deficits caused by WIN55,212-2. Furthermore, a selectivity screening of OS showed high selectivity for CB over various ion channels and receptors. Overall, OS may represent a new approach to the prevention and treatment of learning and memory cognition impairment in neurological diseases.

Cannabidiol and brain function: current knowledge and future perspectives

Cannabidiol (CBD) is a naturally occurring non-psychoactive cannabinoid found in Cannabis sativa, commonly known as cannabis or hemp. Although currently available CBD products do not meet the safety standards of most food safety authorities to be approved as a dietary supplement or food additive, CBD has been gaining widespread attention in recent years due to its various potential health benefits. While primarily known for its therapeutic effects in managing epileptic seizures, psychosis, anxiety, (neuropathic) pain, and inflammation, CBD's influence on brain function has also piqued the interest of researchers and individuals seeking to enhance cognitive performance. The primary objective of this review is to gather, synthesize, and consolidate scientifically proven evidence on the impact of CBD on brain function and its therapeutic significance in treating neurological and mental disorders. First, basic background information on CBD, including its biomolecular properties and mechanisms of action is presented. Next, evidence for CBD effects in the human brain is provided followed by a discussion on the potential implications of CBD as a neurotherapeutic agent. The potential effectiveness of CBD in reducing chronic pain is considered but also in reducing the symptoms of various brain disorders such as epilepsy, Alzheimer's, Huntington's and Parkinson's disease. Additionally, the implications of using CBD to manage psychiatric conditions such as psychosis, anxiety and fear, depression, and substance use disorders are explored. An overview of the beneficial effects of CBD on aspects of human behavior, such as sleep, motor control, cognition and memory, is then provided. As CBD products remain largely unregulated, it is crucial to address the ethical concerns associated with their use, including product quality, consistency, and safety. Therefore, this review discusses the need for responsible research and regulation of CBD to ensure its safety and efficacy as a therapeutic agent for brain disorders or to stimulate behavioral and cognitive abilities of healthy individuals.

Protective Effects of Cannabis in Neuroinflammation-Mediated Alzheimer's Disease

In recent years, Alzheimer's disease (AD) has been recognized as an age-related neurological disorder wherein neurons degenerate and exhibit abnormal structure and function. Aging is the primary factor in the progression of AD from mild to severe cognitive impairment. No effective targeted therapies are presently available, and treatment is limited to symptomatic management. The neuropathologic hallmarks of the disease include the accumulation of amyloid-beta (Aβ) plaques in brain tissues and the aggregation of hyperphosphorylated-tau proteins (tangles) within neurons. Associated hyperactivation of neuroinflammation results in release of inflammatory molecules from neurons, microglia, and astrocytes, which have been linked with neuronal loss and the worsening neurodegeneration. The anti-inflammatory and neuroprotective properties of cannabis-based medicines may offer benefits in delaying the progression of neurodegenerative diseases including AD. This chapter explores the role of cannabinoids in countering neuroinflammation-mediated AD pathology.

Age-dependent effects of estradiol on temporal memory: A role for the type 1 cannabinoid receptor?

This study investigated in male mice how age modulates the effects of acute 17β-estradiol (E2) on dorsal CA1 (dCA1)-dependent retention of temporal associations, which are critical for declarative memory. E2 was systemically injected to young (3-4 months old) and aged (22-24 months old) adult mice either (i) 1 h before the acquisition of an auditory trace fear conditioning (TFC) procedure allowing the assessment of temporal memory retention 24 h later or (ii) during in vivo electrophysiological recordings of CA3 to dCA1 synaptic efficacy under anesthesia. In young mice, E2 induced parallel dose-dependent reductions in memory and synaptic efficacy, i.e. an impairment in TFC retention and a long-term (NMDA receptor-dependent) depression of dCA1 synaptic efficacy as assessed by field excitatory postsynaptic potentials. In contrast, E2 tended to improved TFC retention whilst failing to change synaptic efficacy in aged mice. Age-dependent effects of E2 treatment were confirmed by immunohistochemical analyses of TFC acquisition-elicited dCA1 Fos activation. Thus, such an activation was respectively reduced and enhanced in young and aged E2-treated mice, compared to vehicle treatments. Hippocampal mRNA expression of estrogen receptors by RT-PCR analyses revealed an age-related increase in each receptor mRNA expression. In keeping with the key role of the endocannabinoid system in memory processes and CA3 to dCA1 synaptic plasticity, we next examined the role of cannabinoid type 1 receptors (CB₁-R) in the aforementioned age-dependent effects of E2. Having confirmed that mRNA expression of CB₁-R diminishes with age, we then observed that the deleterious effects of E2 on both memory and synaptic efficacy were both prevented by the CB₁-R antagonist Rimonabant whilst being absent in CB₁-R knock out mice. This study (i) reveals age-dependent effects of acute E2 on temporal memory and CA3 to dCA1 synaptic efficacy and (ii) suggests a key role of CB₁-R in mediating E2 deleterious effects in young adulthood. Aging-related reductions in CB₁-R might thus underlie E2 paradoxical effects across age.

The Influence of CB2-Receptor Ligands on the Memory-Related Responses in Connection with Cholinergic Pathways in Mice in the Passive Avoidance Test

Background: Dysfunction of the cholinergic system is associated with the development of Alzheimer’s disease (AD). One of the new possible strategies for the pharmacological modulation of memory-related problems typical of AD, is connected with the endocannabinoid system (ECS) and the cannabinoid (CB: CB1 and CB2) receptors. Methods: The aim of the study was to determine the influence of the selective CB2 receptor ligands: agonist (JWH 133) and antagonist (AM 630) on different stages of memory and learning in mice, in the context of their interaction with cholinergic pathways. To assess and understand the memory-related effects in mice we used the passive avoidance (PA) test. Results: We revealed that co-administration of non-effective dose of JWH 133 (0.25 mg) or AM 630 (0.25 mg/kg) with the non-effective dose of cholinergic receptor agonist - nicotine (0.05 mg/kg) enhanced cognition in the PA test in mice; however, an acute injection of JWH 133 (0.25 mg/kg) or AM 630 (0.25 mg/kg) had no influence on memory enhancement induced by the effective dose of nicotine (0.1 mg/kg). Co-administration of JWH 133 (0.25 mg) or AM 630 (0.25 mg/kg) with the effective dose of the cholinergic receptor antagonist scopolamine (1 mg/kg) attenuated the scopolamine-induced memory impairment in the PA test in mice. Conclusion: Our experiments have shown that CB2 receptors participate in the modulation of memory-related responses, especially those in which cholinergic pathways are implicated.

Cross state-dependent memory retrieval between cannabinoid CB1 and serotonergic 5-HT1A receptor agonists in the mouse dorsal hippocampus

Understanding the neurobiological mechanisms of drug-related learning and memory formation may help the treatment of cognitive disorders. Dysfunction of the cannabinoid and serotonergic systems has been demonstrated in learning and memory disorders. The present paper investigates the phenomenon called state-dependent memory (SDM) induced by ACPA (a selective cannabinoid CB1 receptor agonist) and 8-OH-DPAT (a nonselective 5-HT1A receptor agonist) with special focus on the role of the 5-HT1A receptor in the effects of both ACPA and 8-OH-DPAT SDM and cross state-dependent memory retrieval between ACPA and 8-OH-DPAT in a step-down inhibitory avoidance task. The dorsal hippocampal CA1 regions of adult male NMRI mice were bilaterally cannulated, and all drugs were microinjected into the intended injection sites. A single-trial step-down inhibitory avoidance task was used to assess memory retrieval and state-dependence. Post-training and/or pre-test microinjections of ACPA (1 and 2 ng/mouse) and 8-OH-DPAT (0.5 and 1 μg/mouse) dose-dependently induced amnesia. Pre-test administration of the same doses of ACPA and 8-OH-DPAT reversed the post-training ACPA- and 8-OH-DPAT-induced amnesia, respectively. This phenomenon has been named SDM. 8-OH-DPAT (1 μg/mouse) reversed the amnesia induced by ACPA (0.5, 1, and 2 ng/mouse) and induced ACPA SDM. ACPA (2 ng/mouse) reversed the amnesia induced by 8-OH-DPAT (0.25, 0.5, and 1 μg/mouse) and induced 8-OH-DPAT SDM. Pre-test administration of a 5-HT1A receptor antagonist, (S)-WAY 100135 (0.25 and 0.5 μg/mouse), 5 min before ACPA and 8-OH-DPAT dose-dependently inhibited ACPA- and 8-OH-DPAT-induced SDM, respectively. The present study results demonstrated ACPA- and 8-OH-DPAT- induced SDM. Overall, the data revealed that dorsal hippocampal 5-HT1A receptor mechanisms play a pivotal role in modulating cross state-dependent memory retrieval between ACPA and 8-OH-DPAT.

The effects of prenatal nicotine and THC E-cigarette exposure on motor development in rats

RATIONALE

In the USA, nicotine and cannabis are the most common licit and illicit drugs used among pregnant women. Importantly, nicotine and cannabis are now being combined for consumption via e-cigarettes, an increasingly popular delivery device. Both nicotine and tetrahydrocannabinol (THC), the primary psychoactive component of cannabis, cross the placenta barrier. However, the consequences of prenatal cannabis use are not well understood, and less is known about potential combination effects when consumed with nicotine, especially via e-cigarettes.

OBJECTIVE

The present study used a rodent model to examine how prenatal e-cigarette exposure to nicotine, THC, and the combination impacts motor development among offspring.

METHODS

Pregnant Sprague-Dawley rats were exposed to nicotine (36 mg/mL), THC (100 mg/mL), the combination, or vehicle via e-cigarette inhalation from gestational days (GD) 5-20. One sex pair per litter was tested on an early sensorimotor development task (postnatal days [PD] 12-20) and a parallel bar motor coordination task (PD 30-32).

RESULTS

Combined prenatal exposure to nicotine and THC delayed sensorimotor development, even though neither drug produced impairments on their own. In contrast, prenatal exposure to either nicotine or THC impaired motor coordination, whereas combined exposure exacerbated these effects, particularly among females.

CONCLUSIONS

These data illustrate that prenatal exposure to either nicotine or THC may alter motor development, and that the combination may produce more severe effects. These findings have important implications for pregnant women as we better understand the teratogenic effects of these drugs consumed via e-cigarettes.

Differential expression of the neuronal CB1 cannabinoid receptor in the hippocampus of male Ts65Dn Down syndrome mouse model

Down syndrome (DS) or Trisomy 21 is the most common genetic cause of mental retardation with severe learning and memory deficits. DS is due to the complete or partial triplication of human chromosome 21 (HSA21) triggering gene overexpression and protein synthesis alterations responsible for a plethora of mental and physical phenotypes. Among the diverse brain target systems that affect hippocampal-dependent learning and memory deficit impairments in DS, the upregulation of the endocannabinoid system (ECS), and notably the overexpression of the cannabinoid type-1 receptor (CB1), seems to play a major role. Combining various protein and gene expression targeted approaches using western blot, qRT-PCR and FISH techniques, we investigated the expression pattern of ECS components in the hippocampus (HPC) of male Ts65Dn mice. Among all the molecules that constitute the ECS, we found that the expression of the CB1 is altered in the HPC of Ts65Dn mice. CB1 distribution is differentially segregated between the dorsal and ventral part of the HPC and within the different cell populations that compose the HPC. CB1 expression is upregulated in GABAergic neurons of Ts65Dn mice whereas it is downregulated in glutamatergic neurons. These results highlight a complex regulation of the CB1 encoding gene (Cnr1) in Ts65Dn mice that could open new therapeutic solutions for this syndrome.

Driving After Cannabis Use Among Young Adults in Michigan

Introduction: Driving after cannabis use is associated with a number of risks. Examination of driving after cannabis use among young adults is particularly important, as young adults have the highest rates of cannabis use and among the highest rates of traffic crashes. The current study examines rates and correlates of driving after cannabis use among young adults (aged 18-25) who reported past month cannabis use. Methods: Participants were from Michigan and recruited through paid Facebook and Instagram advertisements between February and March 2018 (n=461). Results: Nearly a third (31.9%) of the sample reported driving after cannabis use in the past month. Young adults who were employed (aOR=1.872, p=0.045), had medical cannabis cards (aOR=2.877, p<0.001), endorsed coping reasons for use (aOR=2.992, p=0.007), and endorsed social/recreational reasons for use (aOR=1.861, p=0.034) had greater odds of driving after cannabis use. Students had lower odds of driving after use (aOR=0.573, p=0.011). Conclusions: Employment and having a medical cannabis card may be important risk markers for identifying individuals more likely to drive after use of cannabis. Prevention efforts could provide psychoeducation at dispensaries to individuals with medical cannabis cards about the risks of driving after use. Coping motives for cannabis use may also be useful in identifying young adults at the greatest risk of driving after use of cannabis.

Personal and Social Consequences of Psychotropic Substance Use: A Population-Based Internet Survey

Background and objectives: Drug abuse has become a major worldwide health concern among all age groups. The present study analyses substance misuse and its social and personal consequences using a population-based internet survey in Spain. Materials and Methods: Screening for drug abuse (of alcohol, marijuana/hashish and psychostimulants) and its related risks and problems was performed using the Car, Relax, Alone, Forget, Friends, Trouble (CRAFFT) score. Socio-demographic factors, depressive, anxiety and stress symptoms as well as health habits were also evaluated. We used Linear regression methods to compare each variable's individual contribution so as to determine which one best explains the results. Results: In this population-based study, 1224 people completed and returned the online survey. Of all participants, 57% reported consuming at least one substance based on the CRAFFT scale. While increasing age reduces the probability of personal and social consequences of consumption, people who smoke receive up to three times more (OR = 3.370) recommendations from family and friends to reduce their consumption. As for the type of substance, the consumption of marijuana increases the risk of forgetting (OR = 2.33) and the consumption of other psychostimulant substances almost triples the risk of consuming alone (OR = 2.965). Combining substances can increase the rate of driving a vehicle after consumption by 3.4 times. Conclusions: Although age, smoking and the type of substances used increase the risk of suffering from social and personal consequences of the use or abuse of substances, future studies are needed to determine the influence of new variables as a potential tool for treating and minimizing the adverse consequences of drug abuse.

Neuromodulation of Hippocampal-Prefrontal Cortical Synaptic Plasticity and Functional Connectivity: Implications for Neuropsychiatric Disorders

The hippocampus-prefrontal cortex (HPC-PFC) pathway plays a fundamental role in executive and emotional functions. Neurophysiological studies have begun to unveil the dynamics of HPC-PFC interaction in both immediate demands and long-term adaptations. Disruptions in HPC-PFC functional connectivity can contribute to neuropsychiatric symptoms observed in mental illnesses and neurological conditions, such as schizophrenia, depression, anxiety disorders, and Alzheimer's disease. Given the role in functional and dysfunctional physiology, it is crucial to understand the mechanisms that modulate the dynamics of HPC-PFC communication. Two of the main mechanisms that regulate HPC-PFC interactions are synaptic plasticity and modulatory neurotransmission. Synaptic plasticity can be investigated inducing long-term potentiation or long-term depression, while spontaneous functional connectivity can be inferred by statistical dependencies between the local field potentials of both regions. In turn, several neurotransmitters, such as acetylcholine, dopamine, serotonin, noradrenaline, and endocannabinoids, can regulate the fine-tuning of HPC-PFC connectivity. Despite experimental evidence, the effects of neuromodulation on HPC-PFC neuronal dynamics from cellular to behavioral levels are not fully understood. The current literature lacks a review that focuses on the main neurotransmitter interactions with HPC-PFC activity. Here we reviewed studies showing the effects of the main neurotransmitter systems in long- and short-term HPC-PFC synaptic plasticity. We also looked for the neuromodulatory effects on HPC-PFC oscillatory coordination. Finally, we review the implications of HPC-PFC disruption in synaptic plasticity and functional connectivity on cognition and neuropsychiatric disorders. The comprehensive overview of these impairments could help better understand the role of neuromodulation in HPC-PFC communication and generate insights into the etiology and physiopathology of clinical conditions.

Inhibition of CB1 receptor alleviates electroconvulsive shock-induced memory impairment by regulating hippocampal synaptic plasticity in depressive rats

Electroconvulsive therapy (ECT) is one of the most effective treatments for depression, but it can cause cognitive deficit. Unfortunately, effective preventive measures are still lacking. The endocannabinoid system is thought to play a key role in regulation of cognitive process. Whether the endocannabinoid system is involved in the learning and memory impairment caused by ECS remain unclear. In this work, we first found that cannabinoid receptor type 1 (CB1R) and 2-arachidonoylglycerol (2-AG) were strongly expressed in hippocampus by electroconvulsive shock (ECS) in a rat depression model established by chronic mild stress (CMS). Pharmacological inhibition of CB1R using AM251 in vivo resulted in a pronounced relief in ECS-induced spatial learning and memory impairment as well as in a marked reversal of impaired hippocampal long-term potentiation (LTP), and reduced synapse-related proteins expression. Furthermore, results of sucrose preference test (SPT) and open-field test (OFT) showed that AM251 had no significant impact on the therapeutic effects of ECS on pleasure and psychomotor activity. Taken together, we identified that CB1R is involved in the ECS-induced spatial learning and memory impairment and Inhibition of CB1R facilitates the recovery of memory impairment and hippocampal synaptic plasticity, without interfering with the therapeutic effects of ECS in depressed rats.

Allostatic load and the cannabinoid system: implications for the treatment of physiological abnormalities in post-traumatic stress disorder (PTSD)

It is becoming clear that post-traumatic stress disorder (PTSD) is not simply a psychiatric disorder, but one that involves pervasive physiological impairments as well. These physiological disturbances deserve attention in any attempt at integrative treatment of PTSD that requires a focus beyond the PTSD symptoms themselves. The physiological disturbances in PTSD range over many systems, but a common thread thought to underlie them is that the chronic effects of PTSD involve problems with allostatic control mechanisms that result in an excess in what has been termed "allostatic load" (AL). A pharmacological approach to reducing AL would be valuable, but, because of the large range of physiological issues involved - including metabolic, inflammatory, and cardiovascular systems - it is unclear whether there exists a simple comprehensive way to address the AL landscape. In this paper, we propose that the cannabinoid system may offer just such an approach, and we outline evidence for the potential utility of cannabinoids in reducing many of the chronic physiological abnormalities seen in PTSD which are thought to be related to excess AL.

Imbalance of Endocannabinoid/Lysophosphatidylinositol Receptors Marks the Severity of Alzheimer's Disease in a Preclinical Model: A Therapeutic Opportunity

Alzheimer's disease (AD) is the most common form of neurodegeneration and dementia. The endocannabinoid (ECB) system has been proposed as a novel therapeutic target to treat AD. The present study explores the expression of the ECB system, the ECB-related receptor GPR55, and cognitive functions (novel object recognition; NOR) in the 5xFAD (FAD: family Alzheimer's disease) transgenic mouse model of AD. Experiments were performed on heterozygous (HTZ) and homozygous (HZ) 11 month old mice. Protein expression of ECB system components, neuroinflammation markers, and β-amyloid (Aβ) plaques were analyzed in the hippocampus. According to the NOR test, anxiety-like behavior and memory were altered in both HTZ and HZ 5xFAD mice. Furthermore, both animal groups displayed a reduction of cannabinoid (CB1) receptor expression in the hippocampus, which is related to memory dysfunction. This finding was associated with indirect markers of enhanced ECB production, resulting from the combination of impaired monoacylglycerol lipase (MAGL) degradation and increased diacylglycerol lipase (DAGL) levels, an effect observed in the HZ group. Regarding neuroinflammation, we observed increased levels of CB2 receptors in the HZ group that positively correlate with Aβ's accumulation. Moreover, HZ 5xFAD mice also exhibited increased expression of the GPR55 receptor. These results highlight the importance of the ECB signaling for the AD pathogenesis development beyond Aβ deposition.

The relationship between cannabis use and cognition in people diagnosed with first-episode psychosis

Cannabis use is highly prevalent among young people diagnosed with first-episode psychosis (FEP), however, its impact on cognition is still unclear. The aim of the present study was to examine the association of cannabis use with cognition in people diagnosed with FEP. We extended previous research findings by operationalising the comorbid cannabis use, considering recency of cannabis use and use of other illicit substances and including people with a broad spectrum of psychotic diagnoses. A total of 89 people diagnosed with FEP were interviewed about their history of substance use and completed a cognitive test battery assessing verbal memory, verbal fluency and attention. Sixty-one participants were lifetime cannabis users (CU; ≥three times per week for ≥four weeks; 68.5%) and 28 were cannabis non-users (CNU; 31.5%). CU were significantly more likely to be male and exhibited significantly more positive symptoms than CNU. In contrast, CNU displayed significantly more negative symptoms than CU. There were no differences between CU and CNU on neurocognitive tasks of verbal memory, verbal fluency and attention. In conclusion, there was no indication that cannabis use was associated with cognitive impairments in people diagnosed with FEP.

Energetic and thermodynamical aspects of the cyclodextrins-cannabidiol complex in aqueous solution: a molecular-dynamics study

Cyclodextrins (CDs) are well-known carriers for encapsulating hydrophobic molecules, while among cannabinoids, cannabidiol (CBD) has attracted considerable attention due to its therapeutic capability. In this framework, we employed molecular dynamics and docking techniques for investigating the interaction energy and thermodynamical issues between different CDs (α, β, and γ type) and CBD immersed in water and a solution mimicking a physiological environment. We quantified the energetic aspects, for different thermal conditions, in which both aqueous solutions interact with CBDs and CDs and the CBD-CDs complex itself. In order to approximate the physiological conditions, our simulations also included the mammalian temperature. The calculations revealed significant interaction energy between lactate and the CD surface and a movement of lactate toward CD as well. We observed an almost constant number of lactate molecules forming clusters without exhibiting a temperature dependence. Next, the degree of CBD-CDs complexation at four different temperatures was analyzed. The results showed that the complexation depends on the medium, becoming weaker with the temperature increment. Our findings highlighted that the entropy contribution is relevant for CBD-α-CD and CBD-β-CD, while CBD-γ-CD is practically insensitive to temperature changes for both solutions. In both water and artificial physiological solutions, the γ-CD appears more stable than the other complexes. Overall, CBD achieved partial encapsulation considering α-CD and β-CD, showing a temperature dependence, while γ-CD remained fully immersed no matter the thermal level assumed. We also discuss the pharmacological relevance and physiological implications of these findings.

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.

Deleterious Effects of Ethanol, Δ(9)-Tetrahydrocannabinol (THC), and Their Combination on the Spatial Memory and Cognitive Flexibility in Adolescent and Adult Male Rats in the Barnes Maze Task

Research demonstrates that adolescents differ from adults in their response to drugs of abuse. The aim of the present study was to examine the influence of ethanol, Δ9-tetrahydrocannabinol hydrochloride (THC), and a combination of these drugs given during adolescence on spatial memory in adolescent and adult rats. Thus, adolescent rats (postnatal day (PND) 30) were subjected to the following groups: 0.9% NaCl; 1.5 g/kg ethanol; 1.0 mg/kg THC; 1.5 g/kg ethanol + 1.0 mg/kg THC. Rats received drug injection four times at three-day intervals. One day after the last injection, half of the treated animals were tested in the Barnes maze task, whereas the remaining animals were tested on PND 70. Results show that there was a significant age effect on spatial memory in the Barnes maze task after these drug administrations. Adolescent animals demonstrated more potent deficits in the spatial learning and memory (probe trial) and in cognitive flexibility (reversal learning) than did adults. However, in adult rats that received these drugs in adolescence, memory decline was observed only after ethanol and ethanol + THC administration. Thus, our results are important in understanding the deleterious impact of THC and/or ethanol abuse during adolescence on memory function across the lifespan (adolescent versus adult).

Synthesis, biochemical evaluation, and molecular modeling of organophosphate-coumarin hybrids as potent and selective butyrylcholinesterase inhibitors

A small library of new organophosphorylated warfarins and 3-benzylcoumarins were synthesized and evaluated for in vitro cholinesterase inhibition by Ellman's method. Most of the compounds were found to be selective for butyrylcholinesterase (BChE) over acetylcholinesterase (AChE), with IC₅₀ values ranging from 0.363 μM to 53.0 μM determined after 15 s of enzyme exposure. Comparison of the most potent compound, 3b with its constitutional isomer 2b revealed the high importance of phosphate positioning. Reversed selectivity and a 100-fold reduction in anti-BChE activity was observed when the organophosphate was attached to the benzyl instead of the coumarin. Docking calculations suggest that 3b binds initially as a transition state mimic with near-optimal phosphate orientation relative to S198 and occupation of the oxyanion hole prior to phosphorylation. These results might inspire the design of a new type of non-neuropathic and irreversible coumarin-based inhibitor against BChE.

Mobile Assessment of Acute Effects of Marijuana on Cognitive Functioning in Young Adults: Observational Study

Background

Mobile assessment of the effects of acute marijuana on cognitive functioning in the natural environment would provide an ecologically valid measure of the impacts of marijuana use on daily functioning.

Objective

This study aimed to examine the association of reported acute subjective marijuana high (rated 0-10) with performance on 3 mobile cognitive tasks measuring visuospatial working memory (Flowers task), attentional bias to marijuana-related cues (marijuana Stroop), and information processing and psychomotor speed (digit symbol substitution task [DSST]). The effect of distraction as a moderator of the association between the rating of subjective marijuana high and task performance (ie, reaction time and number of correct responses) was explored.

Methods

Young adults (aged 18-25 years; 37/60, 62% female) who reported marijuana use at least twice per week were recruited through advertisements and a participant registry in Pittsburgh, Pennsylvania. Phone surveys and mobile cognitive tasks were delivered 3 times per day and were self-initiated when starting marijuana use. Completion of phone surveys triggered the delivery of cognitive tasks. Participants completed up to 30 days of daily data collection. Multilevel models examined associations between ratings of subjective marijuana high (rated 0-10) and performance on each cognitive task (reaction time and number of correct responses) and tested the number of distractions (rated 0-4) during the mobile task session as a moderator of the association between ratings of subjective marijuana high and task performance.

Results

Participants provided 2703 data points, representing 451 reports (451/2703, 16.7%) of marijuana use. Consistent with slight impairing effects of acute marijuana use, an increase in the average rating of subjective marijuana high was associated with slower average reaction time on all 3 tasks—Flowers (B=2.29; SE 0.86; P=.008), marijuana Stroop (B=2.74; SE 1.09; P=.01), and DSST (B=3.08; SE 1.41; P=.03)—and with fewer correct responses for Flowers (B=−0.03; SE 0.01; P=.01) and DSST (B=−0.18; SE 0.07; P=.01), but not marijuana Stroop (P=.45). Results for distraction as a moderator were statistically significant only for certain cognitive tasks and outcomes. Specifically, as hypothesized, a person’s average number of reported distractions moderated the association of the average rating of subjective marijuana high (over and above a session’s rating) with the reaction time for marijuana Stroop (B=−52.93; SE 19.38; P=.006) and DSST (B=−109.72; SE 42.50; P=.01) and the number of correct responses for marijuana Stroop (B=−0.22; SE 0.10; P=.02) and DSST (B=4.62; SE 1.81; P=.01).

Conclusions

Young adults’ performance on mobile cognitive tasks in the natural environment was associated with ratings of acute subjective marijuana high, consistent with slight decreases in cognitive functioning. Monitoring cognitive functioning in real time in the natural environment holds promise for providing immediate feedback to guide personal decision making.

Fatal crashes in the 5 years after recreational marijuana legalization in Colorado and Washington

Colorado and Washington legalized recreational marijuana in 2012, but the effects of legalization on motor vehicle crashes remains unknown. Using Fatality Analysis Reporting System data, we performed difference-in-differences (DD) analyses comparing changes in fatal crash rates in Washington, Colorado and nine control states with stable anti-marijuana laws or medical marijuana laws over the five years before and after recreational marijuana legalization. In separate analyses, we evaluated fatal crash rates before and after commercial marijuana dispensaries began operating in 2014. In the five years after legalization, fatal crash rates increased more in Colorado and Washington than would be expected had they continued to parallel crash rates in the control states (+1.2 crashes/billion vehicle miles traveled, CI: -0.6 to 2.1, p = 0.087), but not significantly so. The effect was more pronounced and statistically significant after the opening of commercial dispensaries (+1.8 crashes/billion vehicle miles traveled, CI: +0.4 to +3.7, p = 0.020). These data provide evidence of the need for policy strategies to mitigate increasing crash risks as more states legalize recreational marijuana.

Involvement of CB2 Receptors in the Neurobehavioral Effects of Catha Edulis (Vahl) Endl. (Khat) in Mice

There is behavioral evidence for the interaction between crude khat extract and the endocannabinoid system, whereby the endocannabinoid system alters khat extract-mediated behavioral effects through modulation of the monoaminergic system. The objective of this study was to investigate the role of the endocannabinoid system on the neurobehavioral effect of khat extract in mice following concomitant administration of khat extract and the CB2R agonist, JWH133. Locomotor activity test, immunohistochemistry, and reverse transcriptase polymerase chain reaction technique were utilized to assess locomotor activity, tyrosine hydroxylase immunoreactivity, and expression of dopamine transporter mRNA gene. The results show sub-acute administration of khat extract alone increased locomotor activity in mice and co-administration of the CB2R agonist, JWH133, reduced khat extract induced hyperlocomotor activity. The data revealed that cell type specific deletion of CB2Rs on dopaminergic neurons increased the hyperlocomotor behavior of khat extract. Furthermore, the results revealed that khat extract attenuated MPTP induced motor deficits, which is enhanced by JWH133. Khat extract also increased expression of tyrosine hydroxylase positive cells and expression of dopamine transporter mRNA gene in wild type mice. Nevertheless, JWH133 did not alter the effect of khat extract on tyrosine hydroxylase immunoreactivity and dopamine transporter mRNA expression when given together with khat extract. Taken together, the results suggest that the CB2Rs selectively interact with khat extract-mediated locomotor effects and could be utilized as therapeutic target in central nervous system movement disorders associated with dopamine dysregulation.

Cannabis-associated impairments in the fading affect bias and autobiographical memory specificity

We investigated potential relationships between cannabis use and 2 phenomena associated with autobiographical remembering: the fading affect bias (FAB) and memory specificity. The FAB is an emotional affect regulation mechanism that is observed when the intensity of affect associated with experiencing negative memories fades faster than the intensity of affect associated with experiencing positive memories. Memory specificity refers to the level of detail with which events are recalled. No studies have examined the relationships between cannabis use, the FAB, and memory specificity simultaneously. Chronic cannabis users (N = 47) and non-users (N = 52) recalled and described positive and negative autobiographical events and rated the affective intensity for the events at the time of occurrence and at time of test. Participants retrieved additional memories using a sentence-completion recall task, which were coded for specificity. Cannabis users showed reduced fading affect for unpleasant events and reduced memory specificity compared to non-users.

Regional changes in the type 1 cannabinoid receptor are associated with cognitive dysfunction in Parkinson's disease

PURPOSE

The endocannabinoid system plays a regulatory role in a number of physiological functions, including motor control but also mood, emotion, and cognition. A number of preclinical studies in Parkinson's disease (PD) models demonstrated that modulating the type 1 cannabinoid receptor (CB₁R) may improve motor symptoms and components of cognitive processing. However, the relation between CB₁R, cognitive decline and behavioral symptoms has not been investigated in PD patients so far. The aim of this study was to examine whether CB₁R availability is associated with measures of cognitive and behavioral function in PD patients.

METHODS

Thirty-eight PD patients and ten age- and gender-matched controls underwent a [¹⁸F]MK-9470 PET scan to assess CB₁R availability, as well as volumetric MR imaging. Neuropsychological symptoms were evaluated using an extensive cognitive and behavioral battery covering the five cognitive domains, depression, anxiety, apathy, and psychiatric complications, and were correlated to CB₁R availability using vowel-wise regression analysis (P < 0.05, corrected for familywise error).

RESULTS

PD patients with poorer performance in episodic memory, executive functioning, speed and mental flexibility (range P 0.003-0.03) showed lower CB₁R availability in predominantly the midcingulate cortex and middle to superior frontal gyrus (T_peak-level > 4.0). Also, PD patients with more severe visuospatial dysfunction showed decreased CB₁R availability in the precuneus, midcingulate, supplementary motor cortex, inferior orbitofrontal gyrus and thalamus (T_peak-level = 5.5). These correlations were not related to cortical gray matter atrophy. No relationship was found between CB₁R availability and mood or behavioral symptom scores.

CONCLUSIONS

Decreased CB₁R availability in the prefrontal and midcingulate cortex in PD patients is strongly correlated with disturbances in executive functioning, episodic memory, and visuospatial functioning. Further investigation of regional CB1R expression in groups of PD patients with mild cognitive impairment or dementia is warranted in order to further investigate the role of CB1R expression in different levels of cognitive impairment in PD.

Spontaneous, anecdotal, retrospective, open-label study on the efficacy, safety and tolerability of cannabis galenical preparation (Bedrocan)

OBJECTIVES

Our main aim was to investigate the short-term therapeutic effects, safety/tolerability and potential side effects of the cannabis galenical preparation (Bedrocan) in patients with a range of chronic conditions unresponsive to other treatments.

METHODS

In this retrospective, 'compassionate use', observational, open-label study, 20 patients (age 18-80 years) who had appealed to our 'Second Opinion Medical Consulting Network' (Modena, Italy), were instructed to take sublingually the galenical oil twice a day for 3 months of treatment. The usual starting dose was low (0.5 ml/day) and gradually titrated upward to the highest recommended dose (1 ml/day). Tolerability and adverse effects were assessed at baseline and monthly thereafter during the treatment period through direct contact (email or telephone) or visit if required. Patients' quality of life was evaluated at baseline and 3 months using the medical outcome short-form health survey questionnaire (SF-36).

KEY FINDINGS

From baseline to 6 months post-treatment, SF-36 scores showed: reductions in total pain (P < 0.03); improvements in the physical component (P < 0.02); vitality (P < 0.03); social role functioning (P < 0.02); and general health state (P < 0.02). No changes in role limitations (P = 0.02) due to emotional state (e.g. panic, depression, mood alteration) were reported. Monthly reports of psychoactive adverse effects showed significant insomnia reduction (P < 0.03) and improvement in mood (P < 0.03) and concentration (P < 0.01).

CONCLUSIONS

These data suggest that a cannabis galenical preparation may be therapeutically effective and safe for the symptomatic treatment of some chronic diseases. Further studies on the efficacy of cannabis as well as cannabinoid system involvement in the pathophysiology are warranted.

The Endocannabinoid System as a Potential Mechanism through which Exercise Influences Episodic Memory Function

Emerging research demonstrates that exercise, including both acute and chronic exercise, may influence episodic memory function. To date, mechanistic explanations of this effect are often attributed to alterations in long-term potentiation, neurotrophic production, angiogenesis, and neurogenesis. Herein, we discuss a complementary mechanistic model, suggesting that the endocannabinoid system may, in part, influence the effects of exercise on memory function. We discuss the role of the endocannabinoid system on memory function as well as the effects of exercise on endocannabinoid alterations. This is an exciting line of inquiry that should help delineate new insights into the mechanistic role of exercise on memory function.

Role of Cannabinoid Receptor Type 1 in Insulin Resistance and Its Biological Implications

Endogenous cannabinoids (ECs) are lipid-signaling molecules that specifically bind to cannabinoid receptor types 1 and 2 (CB1R and CB2R) and are highly expressed in central and many peripheral tissues under pathological conditions. Activation of hepatic CB1R is associated with obesity, insulin resistance, and impaired metabolic function, owing to increased energy intake and storage, impaired glucose and lipid metabolism, and enhanced oxidative stress and inflammatory responses. Additionally, blocking peripheral CB1R improves insulin sensitivity and glucose metabolism and also reduces hepatic steatosis and body weight in obese mice. Thus, targeting EC receptors, especially CB1R, may provide a potential therapeutic strategy against obesity and insulin resistance. There are many CB1R antagonists, including inverse agonists and natural compounds that target CB1R and can reduce body weight, adiposity, and hepatic steatosis, and those that improve insulin sensitivity and reverse leptin resistance. Recently, the use of CB1R antagonists was suspended due to adverse central effects, and this caused a major setback in the development of CB1R antagonists. Recent studies, however, have focused on development of antagonists lacking adverse effects. In this review, we detail the important role of CB1R in hepatic insulin resistance and the possible underlying mechanisms, and the therapeutic potential of CB1R targeting is also discussed.

Quantitation of Cannabinoids in Breath Samples Using a Novel Derivatization LC–MS/MS Assay with Ultra-High Sensitivity

As the legalization of medical and recreational marijuana use expands, measurement of tetrahydrocannabinol (THC) in human breath has become an area of interest. The presence and concentration of cannabinoids in breath have been shown to correlate with recent marijuana use and may be correlated with impairment. Given the low concentration of THC in human breath, sensitive analytical methods are required to further evaluate its utility and window of detection. This paper describes a novel derivatization method based on an azo coupling reaction that significantly increases the ionization efficiency of cannabinoids for LC–MS/MS analysis. This derivatization reaction allows for a direct derivatization reaction with neat samples and does not require further sample clean-up after derivatization, thus facilitating an easy and rapid “derivatize & shoot” sample preparation. The derivatization assay allowed for limits of quantitation (LOQ’s) in the sub-pg/mL to pg/mL range for the five cannabinoids in breath samples, i.e., only 5~50 femtograms of an analyte was required for quantitation in a single analysis. This ultrahigh sensitivity allowed for the quantitation of cannabinoids in all breath samples collected within 3 hours of smoking cannabis (n = 180). A linear correlation between THC and cannabinol (CBN) in human breath was observed, supporting the hypothesis that CBN is converted from THC during the combustion of cannabis. The derivatization method was also applied to the analysis of cannabinoids in whole blood samples, achieving LOQ’s at ten-pg/mL to sub-ng/mL level. This azo coupling-based derivatization approach provided the needed analytical sensitivity for the analysis of THC in human breath samples using LC–MS/MS and could be a valuable tool for the analysis of other aromatic compounds in the future.

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.

Cannabis use and driving-related performance in young recreational users: a within-subject randomized clinical trial

BACKGROUND

With the legalization of cannabis in Canada, young adults, who are already at risk of automobile crashes, may increase their use of cannabis, which may further increase the risk of crashes. We examined the effects of inhaled cannabis on driving-related performance in healthy 18- to 24-year-old recreational cannabis users.

METHODS

In this within-subject randomized study, participants completed tests in the no-cannabis state and at 1, 3 and 5 hours after inhalation of a standard 100-mg dose of cannabis. We then measured performance (in useful-field-of-view and driving-simulation tests) and self-reported perceptions (driving ability and safety, cannabis effects). Repeated-measures analysis of variance (for cannabis effects on continuous performance measures), Cochran Q tests (for performance-related crash risk and binary complex simulator task scores) and correlational analyses (for self-reported perceptions relative to performance) were employed.

RESULTS

Forty-five participants completed all 180 testing sessions. Significant effects of cannabis (relative to no cannabis) were noted on complex useful-field-of-view tasks at 3 hours (complex divided-attention task: 70 ± 24 ms v. 37 ± 12 ms, 95% confidence intervals [CIs] 28-114 ms v. 29-45 ms, t = -2.98, df = 41, p = 0.005; complex selective-attention task: 102 ± 66 ms v. 64 ± 18 ms, 95% CIs 60-144 ms v. 53-75 ms, t = -2.42, df = 41, p = 0.02) and 5 hours (complex selective-attention task: 82 ± 29 ms v. 61 ± 19 ms, 95% CIs 62-100 ms v. 48-75 ms, t = -2.32, df = 41, p = 0.03) after cannabis use when the tasks were novel (performed in a cannabis state at the first session). Participants were significantly more likely to be classified as having a high crash risk (on the basis of simulator tasks) after cannabis use (χ ² = 13.23, df = 1, p < 0.001, odds ratio 4.31, 95% CI 0.41-45.2) and reported significantly lower perceived driving ability and safety after cannabis use relative to non-use.

INTERPRETATION

Among young recreational cannabis users, a 100-mg dose of cannabis by inhalation had no effect on simple driving-related tasks, but there was significant impairment on complex tasks, especially when these were novel. These effects, along with lower self-perceived driving ability and safety, lasted up to 5 hours after use.

TRIAL REGISTRATION

The trial was registered with Health Canada (NOL [No Objection Letter] no. 215101).

The effects of cannabidiol (CBD) on cognition and symptoms in outpatients with chronic schizophrenia a randomized placebo controlled trial

RATIONALE

Preliminary evidence suggests that cannabidiol (CBD) may be effective in the treatment of neurodegenerative disorders; however, CBD has never been evaluated for the treatment of cognitive impairments associated with schizophrenia (CIAS).

OBJECTIVE

This study compared the cognitive, symptomatic, and side effects of CBD versus placebo in a clinical trial.

METHODS

This study was a 6-week, randomized, placebo-controlled, parallel group, fixed-dose study of oral CBD (600 mg/day) or placebo augmentation in 36 stable antipsychotic-treated patients diagnosed with chronic schizophrenia. All subjects completed the MATRICS Consensus Cognitive Battery (MCCB) at baseline and at end of 6 weeks of treatment. Psychotic symptoms were assessed using the Positive and Negative Syndrome Scale (PANSS) at baseline and biweekly.

RESULTS

There was no main effect of time or drug on MCCB Composite score, but a significant drug × time effect was observed (p = 0.02). Post hoc analyses revealed that only placebo-treated subjects improved over time (p = 0.03). There was a significant decrease in PANSS Total scores over time (p < 0. 0001) but there was no significant drug × time interaction (p = 0.18). Side effects were similar between CBD and placebo, with the one exception being sedation, which was more prevalent in the CBD group.

CONCLUSIONS

At the dose studied, CBD augmentation was not associated with an improvement in MCCB or PANSS scores in stable antipsychotic-treated outpatients with schizophrenia. Overall, CBD was well tolerated with no worsening of mood, suicidality, or movement side effects.

TRIAL REGISTRATION

https://clinicaltrials.gov/ct2/show/NCT00588731.

Cross state-dependency of learning between arachidonylcyclopropylamide (ACPA) and muscimol in the mouse dorsal hippocampus

The aim of the present study was to examine cross state-dependent learning between ACPA (a selective cannabinoid CB1 receptor agonist) and muscimol (a selective GABAA receptor agonist) in the step-down inhibitory avoidance learning task. The dorsal hippocampal CA1 regions of adult male NMRI mice were bilaterally cannulated, and all drugs were microinjected into the intended sites of injection. Post-training and/or pre-test administration of ACPA (1 and 2ng/mouse) dose-dependently induced amnesia. Pre-test microinjection of the same doses of ACPA reversed the post-training ACPA-induced amnesia. This event has been named ACPA state-dependent learning (SDL). Post-training and/or pre-test microinjection of muscimol (0.05 and 0.1μg/mouse) dose-dependently induced amnesia. Pre-test administration of the same doses of muscimol reversed the post-training muscimol-induced amnesia, suggesting muscimol SDL. The amnesia induced by post-training administration of ACPA was reversed by pre-test administration of muscimol (0.05 and 0.1μg/mouse). Furthermore, the pre-test microinjection of muscimol (0.025 and 0.05μg/mouse) with an ineffective dose of ACPA (0.5ng/mouse) significantly restored memory retrieval and induced ACPA SDL. In another series of experiments, the amnesia induced by post-training administration of muscimol was reversed by pre-test administration of ACPA (1 and 2ng/mouse). Moreover, pre-test microinjection of ACPA (0.5 and 1ng/mouse) with an ineffective dose of muscimol (0.025μg/mouse) significantly restored memory retrieval and induced muscimol SDL. It is important to note that pre-test intra-CA1 injection of a selective GABAA receptor antagonist, bicuculline (0.125 and 0.25μg/mouse), 5min before the administration of muscimol (0.1μg/mouse) or ACPA (2ng/mouse) dose-dependently inhibited muscimol- and ACPA-induced SDL, respectively. Pre-test intra-CA1 administration of bicuculline (0.0625, 0.125 and 0.25μg/mouse) by itself did not affect memory retention. In conclusion, the data strongly revealed a cross SDL among ACPA and muscimol in the dorsal hippocampal CA1 regions.

The FAAH inhibitor URB597 suppresses hippocampal maximal dentate afterdischarges and restores seizure-induced impairment of short and long-term synaptic plasticity

Synthetic cannabinoids and phytocannabinoids have been shown to suppress seizures both in humans and experimental models of epilepsy. However, they generally have a detrimental effect on memory and memory-related processes. Here we compared the effect of the inhibition of the endocannabinoid (eCB) degradation versus synthetic CB agonist on limbic seizures induced by maximal dentate activation (MDA) acute kindling. Moreover, we investigated the dentate gyrus (DG) granule cell reactivity and synaptic plasticity in naïve and in MDA-kindled anaesthetised rats. We found that both the fatty acid amide hydrolase (FAAH) inhibitor URB597 and the synthetic cannabinoid agonist WIN55,212-2 displayed AM251-sensitive anti-seizure effects. WIN55,212-2, dose-dependently (0.5-2 mg/kg, i.p.) impaired short-term plasticity (STP) and long-term potentiation (LTP) at perforant path-DG synapses in naïve rats. Strikingly, URB597 (1 mg/kg, i.p.) was devoid of any deleterious effects in normal conditions, while it prevented seizure-induced alterations of both STP and LTP. Our evidence indicates that boosting the eCB tone rather than general CB1 activation might represent a potential strategy for the development of a new class of drugs for treatment of both seizures and comorbid memory impairments associated with epilepsy.

Cannabinoid Modulation of Memory Consolidation in Rats: Beyond the Role of Cannabinoid Receptor Subtype 1

The effects induced by exogenous manipulation of endocannabinoid neurotransmission on emotion and memory are often contradictory. Among the different factors involved, of particular interest is the binding affinity of endocannabinoids, and their analogs, for other receptor families beyond cannabinoid receptors, such as the peroxisome proliferator-activated receptors (PPARs), and the transient receptor potential cation channel subfamily V member 1 (TRPV1). The aim of this study was to investigate which receptor subtype mediates cannabinoid effects on memory consolidation for emotionally arousing experiences. We tested two cannabinoid compounds with different pharmacological properties in the inhibitory avoidance task, and evaluated whether the observed effects are mediated by cannabinoid, PPARα or TRPV1 receptor activation. We found that the synthetic cannabinoid agonist WIN55,212-2 and the FAAH inhibitor URB597 both enhanced memory consolidation for inhibitory avoidance training. WIN55,212-22 effects on memory consolidation were predominantly mediated by CB1 receptor activation but CB2 receptors were involved as well. The URB597-induced memory enhancement was dependent on the activation not only of CB1 and CB2 receptors but, notwithstanding, PPAR-α and TRPV1 receptors were involved as well. Our findings drive beyond the classical hypothesis centered on the unique role of CB1 receptor activation for cannabinoid effects on memory, and reveal new insights in the neural mechanisms of memory consolidation.

Endocannabinoid System: the Direct and Indirect Involvement in the Memory and Learning Processes-a Short Review

The endocannabinoid system via cannabinoid (CB: CB1 and CB2) receptors and their endogenous ligands is directly and indirectly involved in many physiological functions, especially in memory and learning processes. Extensive studies reported that this system strictly modulates cognition-related processes evaluated in various animal models. However, the effects of cannabinoids on the cognition have been contradictory. The cannabinoid compounds were able to both impair or improve different phases of memory processes through direct (receptor related) or indirect (non-receptor related) mechanism. The memory-related effects induced by the cannabinoids can be depended on the kind of cannabinoid compound used, dosage, and route of administration as well as on the memory task chosen. Therefore, the objectives of this paper are to review and summarize the results describing the role of endocannabinoid system in cognition, including various stages of memory.

Involvement of medial prefrontal cortex alpha-2 adrenoceptors on memory acquisition deficit induced by arachidonylcyclopropylamide, a cannabinoid CB1 receptor agonist, in rats; possible involvement of Ca2+ channels

Functional interactions between cannabinoid and alpha-2 adrenergic systems in cognitive control in the medial prefrontal cortex (mPFC) seem possible. The present study evaluated the possible role of alpha-2 adrenoceptors of the prefrontal cortex on effect of arachidonylcyclopropylamide (ACPA), a cannabinoid CB1 receptor (CB1R) agonist, in adult male Wistar rats. The animals were bilaterally implanted with chronic cannulae in the mPFC, trained in a step-through task, and tested 24 h after training to measure step-through latency. Results indicate that pre-training microinjection of ACPA (0.05 and 0.5 μg/rat) and clonidine (alpha-2 adrenoceptor agonist; 1 and 2 μg/rat) reduce memory acquisition. Pre-training subthreshold dose of clonidine (0.5 µg/rat) restored memory-impairing effect of ACPA (0.05 and 0.5 µg/rat). On the other hand, pre-training administration of the alpha-2 adrenoceptor antagonist yohimbine in all doses used (0.5, 1, and 2 μg/rat) did not affect memory acquisition by itself, while a subthreshold dose of yohimbine (2 µg/rat) potentiated memory impairment induced by ACPA (0.005 µg/rat). Finally, a subthreshold dose of SKF96365 (a Ca(2+) channel blocker) blocked clonidine and yohimbine effect of memory responses induced by ACPA. In conclusion, these data indicate that mPFC alpha-2 adrenoceptors play an important role in ACPA-induced amnesia and Ca(2+) channels have a critical role this phenomenon.

Elevation of Plasma 2-Arachidonoylglycerol Levels in Alzheimer's Disease Patients as a Potential Protective Mechanism against Neurodegenerative Decline

BACKGROUND

Growing evidence suggests that the endocannabinoid system is involved in the pathogenesis of Alzheimer's disease (AD) and atherosclerosis.

OBJECTIVE

The purpose of this study was to investigate the activation of the endocannabinoid system in AD in vivo and the possible intermediate role of atherosclerosis.

METHODS

We enrolled 41 patients with probable AD, and 30 age- and gender-matched controls. All subjects underwent: ultrasound examination of cerebral and neck vessels (including intima-media thickness and plaque stenosis evaluation); blood sampling to measure levels of endocannabinoid [anandamide (AEA), 2-arachidonoylglycerol (2-AG)] and endogenous AEA analogues [N-palmitoyl-ethanolamide (PEA); N-oleoyl-ethanolamide]; neuropsychological evaluation and brain MRI (atrophy, white matter hyperintensity volume).

RESULTS

2-AG levels were higher in AD patients compared to controls (Mann-Whitney test p = 0.021). In the AD group, 2-AG correlated to white matter hyperintensity volume (r = 0.415, p = 0.015) and was higher in patients with chronic heart ischemic disease (p = 0.023). In AD patients, 2-AG was also positively related to memory (r = 0.334, p = 0.05) and attention (r = 0.423, p = 0.018) performances. Constructional praxia test scores were lower in patients with higher levels of PEA (r =-0.389, p = 0.019).

CONCLUSION

AD patients present high plasma 2-AG levels, also in relation to heart ischemic disease and cerebral leukoaraiosis. This may be a protective mechanism hindering neurodegeneration, but it may also play an ambivalent role on cerebrovascular circulation. The increase in 2-AG and PEA levels observed with ongoing pathological processes may differently modulate cognitive performances.