Modulation of Δ9-THC-induced increase of cortical and hippocampal acetylcholine release by μ opioid and D1 dopamine receptors

Real world clinical outcomes of treatment of cannabis-induced psychosis and prevalence of cannabis-related primary psychosis: a retrospective study

BACKGROUND

Current treatment of cannabis-induced psychosis (CIP) focus on the presenting symptoms of individual patient. Therefore, the objective of this study was to investigate the efficacy of pharmacological treatment for CIP in a retrospective manner.

METHODS

A retrospective chart review study was conducted at the Princess Mother National Institute on Drug Abuse Treatment (PMNIDAT), Thailand. Patients aged more than 12 years who met the International Classification of Disease-10 (ICD-10) criteria of CIP, had recorded of cannabis use in medical chart, and had positive urine test of cannabis on the first day of admission from October 2013 to September 2019 were enrolled. The primary outcome was the efficacy of pharmacological treatment of CIP. Brief Psychotic Rating Scale (BPRS) on the first day and weekly after receiving treatment were used to assess the primary outcome.

RESULTS

Four hundred and three medical charts with diagnosis of CIP were enrolled into the study and only 317 charts were analyzed. Most of them were male with an average aged of 21.0 (19.0-24.0) years old. All of them used smoked cannabis from dried leaves and flowers of cannabis plant. The presented symptoms on admission were psychosis, mood symptoms, sleep problems, weight loss, and cognitive problems (100%, 64%, 61%, 11%, and 7%, respectively). Baseline BPRS score of the first day of admission was 55.2 ± 9.6. Majority of patients received antipsychotic (98.7%) followed by the combination of antipsychotics with benzodiazepines (34.5.%), antipsychotics with antidepressants (14.4%) and antipsychotics treatment with antidepressants and benzodiazepines (25.9%). Only few patients received antipsychotic monotherapy (17.9%). Risperidone was the most frequently prescribed antipsychotics (83.6%). Mean equivalence dose of risperidone was 8.0 ± 5.9 mg/day. The average hospital length of stay was 28 days (range 22-31). BPRS at 22 days significantly improved compared to the first day of admission (p < 0.001). Schizophrenia was diagnosed in 7% at 1.3 years of follow up.

CONCLUSION

Antipsychotics was still a key psychotropic drug for treatment of CIP. The symptoms were decreased rapidly and sustained among the treatment period. However, antidepressants and benzodiazepines were commonly used for treatment of other symptoms beyond psychosis.

TRIAL REGISTRATION

ClinicalTrials.gov ID: NCT04945031 (Registration Date: 30 June, 2021).

A brain imaging study of dopamine receptor D2 availability in cannabis dependent users after recovery from cannabis-induced psychosis

There is increased risk of psychosis associated with cannabis use disorder and the interaction of THC with dopamine neurotransmission is complex. It is important to investigate the recovery from cannabis-induced psychosis and its effects on the brain's dopamine neurotransmission. This study was to evaluate dopamine receptor D2 availability in the striatum (caudate/putamen) in recently abstinent cannabis dependent users after recovery from psychosis in comparison with abstinent MDMA "ecstasy" abusers and healthy control participants. Participants were eight abstinent ex cannabis-dependent users who were treated for cannabis-induced psychosis with anti-psychotic medication and psychosocial support for 4 months in an inpatient treatment center for drug users. They were compared with nine abstinent ex MDMA "ecstasy" abusers who received medication and psycho-social treatment for 4 months at the same treatment facility and eight healthy control participants. All participants were scanned with bolus and constant infusion of [123I] Iodobenzamide (IBZM) in Single Photon Computed Tomography (SPECT). Cannabis abstinent users who were treated for cannabis-induced psychotic episodes showed no difference in dopamine D2 receptor availability in the caudate compared with abstinent MDMA "ecstasy" abusers and healthy control participants. This finding indicates minimal effects of cannabis-induced psychosis on dopamine reward mechanisms. There is evidence for reduced D2 receptor availability measures in the right putamen (uncorrected) which may indicate a residual effect of anti-psychotic medication.

ASRA Pain Medicine consensus guidelines on the management of the perioperative patient on cannabis and cannabinoids

BACKGROUND

The past two decades have seen an increase in cannabis use due to both regulatory changes and an interest in potential therapeutic effects of the substance, yet many aspects of the substance and their health implications remain controversial or unclear.

METHODS

In November 2020, the American Society of Regional Anesthesia and Pain Medicine charged the Cannabis Working Group to develop guidelines for the perioperative use of cannabis. The Perioperative Use of Cannabis and Cannabinoids Guidelines Committee was charged with drafting responses to the nine key questions using a modified Delphi method with the overall goal of producing a document focused on the safe management of surgical patients using cannabinoids. A consensus recommendation required ≥75% agreement.

RESULTS

Nine questions were selected, with 100% consensus achieved on third-round voting. Topics addressed included perioperative screening, postponement of elective surgery, concomitant use of opioid and cannabis perioperatively, implications for parturients, adjustment in anesthetic and analgesics intraoperatively, postoperative monitoring, cannabis use disorder, and postoperative concerns. Surgical patients using cannabinoids are at potential increased risk for negative perioperative outcomes.

CONCLUSIONS

Specific clinical recommendations for perioperative management of cannabis and cannabinoids were successfully created.

Enhancing effect of nicotine on electrical field stimulation elicited contractile responses in isolated rabbit bladder straight muscle; the role of cannabinoid and vanilloid receptors

BACKGROUND

Nicotine acts as an agonist of nicotinic acetylcholine receptors (nAChR). These receptors belong to a superfamily of ligand-gated ion channels. We previously demonstrated that nicotine increased electrical field stimulation (EFS)-induced contractile or relaxation responses, possibly by facilitating neurotransmitter release from nerve terminals in various rabbit tissues. Studies have shown that there is an interaction between the endocannabinoid and nicotinic systems. This study aimed to investigate the interaction between nicotine and the endocannabinoid system in the rabbit urine bladder and also investigate the enhancing effect of nicotine on EFS-induced contractile responses in rabbit isolated bladder smooth muscle and its interaction with the endocannabinoid system.

METHODS

The New Zealand albino male adult rabbits were used for this study. Following scarification, the urine bladder was rapidly excised, and then uniform strips were prepared. Each strip was mounted under 1 g isometric resting tension in an organ bath containing 20 mL of Krebs-Henseleit solution. After obtaining EFS-induced contractile responses, 10-4 M concentrations of nicotine were applied to the preparations, and EFS was stopped after 5 stimulations. Following washing, the same experimental procedure was performed with the same tissue in the presence of AM251 (a cannabinoid CB1R antagonist, 10-6 M), AM630 (a cannabinoid CB2R antagonist, 10-6 M), and capsazepine (a vanilloid receptor antagonist, 3 × 10-6 M).

RESULTS

Nicotine enhanced the EFS-induced contraction responses by 17.16% ± 2.81% at a 4-Hz stimulation frequency. Cannabinoid receptor antagonists AM251 and AM630 reduced this increasing effect of nicotine although it was not significant and vanilloid receptor antagonist capsazepine did not significantly alter the nicotines' effect.

DISCUSSION

These results show that enhancing effect of nicotine in the smooth muscle of the rabbit bladder, even though it was not significant endocannabinoid system possibly have a role in nicotines' effect.

Interactions between the Nicotinic and Endocannabinoid Receptors at the Plasma Membrane

Compartmentalization, together with transbilayer and lateral asymmetries, provide the structural foundation for functional specializations at the cell surface, including the active role of the lipid microenvironment in the modulation of membrane-bound proteins. The chemical synapse, the site where neurotransmitter-coded signals are decoded by neurotransmitter receptors, adds another layer of complexity to the plasma membrane architectural intricacy, mainly due to the need to accommodate a sizeable number of molecules in a minute subcellular compartment with dimensions barely reaching the micrometer. In this review, we discuss how nature has developed suitable adjustments to accommodate different types of membrane-bound receptors and scaffolding proteins via membrane microdomains, and how this "effort-sharing" mechanism has evolved to optimize crosstalk, separation, or coupling, where/when appropriate. We focus on a fast ligand-gated neurotransmitter receptor, the nicotinic acetylcholine receptor, and a second-messenger G-protein coupled receptor, the cannabinoid receptor, as a paradigmatic example.

Nanoscale Sub-Compartmentalization of the Dendritic Spine Compartment

Compartmentalization of the membrane is essential for cells to perform highly specific tasks and spatially constrained biochemical functions in topographically defined areas. These membrane lateral heterogeneities range from nanoscopic dimensions, often involving only a few molecular constituents, to micron-sized mesoscopic domains resulting from the coalescence of nanodomains. Short-lived domains lasting for a few milliseconds coexist with more stable platforms lasting from minutes to days. This panoply of lateral domains subserves the great variety of demands of cell physiology, particularly high for those implicated in signaling. The dendritic spine, a subcellular structure of neurons at the receiving (postsynaptic) end of central nervous system excitatory synapses, exploits this compartmentalization principle. In its most frequent adult morphology, the mushroom-shaped spine harbors neurotransmitter receptors, enzymes, and scaffolding proteins tightly packed in a volume of a few femtoliters. In addition to constituting a mesoscopic lateral heterogeneity of the dendritic arborization, the dendritic spine postsynaptic membrane is further compartmentalized into spatially delimited nanodomains that execute separate functions in the synapse. This review discusses the functional relevance of compartmentalization and nanodomain organization in synaptic transmission and plasticity and exemplifies the importance of this parcelization in various neurotransmitter signaling systems operating at dendritic spines, using two fast ligand-gated ionotropic receptors, the nicotinic acetylcholine receptor and the glutamatergic receptor, and a second-messenger G-protein coupled receptor, the cannabinoid receptor, as paradigmatic examples.

Cannabis and Autoimmunity: Possible Mechanisms of Action

Medical cannabis (MC) describes the usually inhaled or ingested use of a cannabis plant or cannabis extract for medicinal purposes. The action of whole cannabis plants is extremely complex because their large number of active compounds not only bind to a plethora of different receptors but also interact with each other both synergistically and otherwise. Renewed interest in the medicinal properties of cannabis has led to increasing research into the practical uses of cannabis derivatives, and it has been found that the endocannabinoid system (particularly CB2 receptor activation) is a possible target for the treatment of inflammatory and the autoimmune diseases related to immune cell activation. However, in vivo findings still lack, creating difficulties in applying translational cannabinoid research to human immune functions. In this review, we summarized the main mechanisms of action of medical cannabis plant especially regarding the immune system and the endocannabinoid system, looking at preliminary clinical data in three most important autoimmune diseases of three different specialities: rheumatoid arthritis, multiple sclerosis and inflammatory bowel disease.

Interaction of Cannabis Use and Aging: From Molecule to Mind

Given the aging Baby Boomer generation, changes in cannabis legislation, and the growing acknowledgment of cannabis for its therapeutic potential, it is predicted that cannabis use in the older population will escalate. It is, therefore, important to determine the interaction between the effects of cannabis and aging. The aim of this report is to describe the link between cannabis use and the aging brain. Our review of the literature found few and inconsistent empirical studies that directly address the impact of cannabis use on the aging brain. However, research focused on long-term cannabis use points toward cumulative effects on multimodal systems in the brain that are similarly affected during aging. Specifically, the effects of cannabis and aging converge on overlapping networks in the endocannabinoid, opioid, and dopamine systems that may affect functional decline particularly in the hippocampus and prefrontal cortex, which are critical areas for memory and executive functioning. To conclude, despite the limited current knowledge on the potential interactive effects between cannabis and aging, evidence from the literature suggests that cannabis and aging effects are concurrently present across several neurotransmitter systems. There is a great need for future research to directly test the interactions between cannabis and aging.

Analysis of natural product regulation of cannabinoid receptors in the treatment of human disease

The organized, tightly regulated signaling relays engaged by the cannabinoid receptors (CBs) and their ligands, G proteins and other effectors, together constitute the endocannabinoid system (ECS). This system governs many biological functions including cell proliferation, regulation of ion transport and neuronal messaging. This review will firstly examine the physiology of the ECS, briefly discussing some anomalies in the relay of the ECS signaling as these are consequently linked to maladies of global concern including neurological disorders, cardiovascular disease and cancer. While endogenous ligands are crucial for dispatching messages through the ECS, there are also commonalities in binding affinities with copious exogenous ligands, both natural and synthetic. Therefore, this review provides a comparative analysis of both types of exogenous ligands with emphasis on natural products given their putative safer efficacy and the role of Δ9-tetrahydrocannabinol (Δ9-THC) in uncovering the ECS. Efficacy is congruent to both types of compounds but noteworthy is the effect of a combination therapy to achieve efficacy without unideal side-effects. An example is Sativex that displayed promise in treating Huntington's disease (HD) in preclinical models allowing for its transition to current clinical investigation. Despite the in vitro and preclinical efficacy of Δ9-THC to treat neurodegenerative ailments, its psychotropic effects limit its clinical applicability to treating feeding disorders. We therefore propose further investigation of other compounds and their combinations such as the triterpene, α,β-amyrin that exhibited greater binding affinity to CB₁ than CB₂ and was more potent than Δ9-THC and the N-alkylamides that exhibited CB₂ selective affinity; the latter can be explored towards peripherally exclusive ECS modulation. The synthetic CB₁ antagonist, Rimonabant was pulled from commercial markets for the treatment of diabetes, however its analogue SR144528 maybe an ideal lead molecule towards this end and HU-210 and Org27569 are also promising synthetic small molecules.

Interactions between the endocannabinoid and nicotinic cholinergic systems: preclinical evidence and therapeutic perspectives

RATIONALE

Several lines of evidence suggest that endocannabinoid and nicotinic cholinergic systems are implicated in the regulation of different physiological processes, including reward, and in the neuropathological mechanisms of psychiatric diseases, such as addiction. A crosstalk between these two systems is substantiated by the overlapping distribution of cannabinoid and nicotinic acetylcholine receptors in many brain structures.

OBJECTIVE

We will review recent preclinical data showing how the endocannabinoid and nicotinic cholinergic systems interact bidirectionally at the level of the brain reward pathways, and how this interaction plays a key role in modulating nicotine and cannabinoid intake and dependence.

RESULTS

Many behavioral and neurochemical effects of nicotine that are related to its addictive potential are reduced by pharmacological blockade or genetic deletion of type-1 cannabinoid receptors, inhibition of endocannabinoid uptake or metabolic degradation, and activation of peroxisome proliferator-activated-receptor-α. On the other hand, cholinergic antagonists at α7 nicotinic acetylcholine receptors as well as endogenous negative allosteric modulators of these receptors are effective in blocking dependence-related effects of cannabinoids.

CONCLUSIONS

Pharmacological manipulation of the endocannabinoid system and endocannabinoid-like neuromodulators shows promise in the treatment of nicotine dependence and in relapse prevention. Likewise, drugs acting at nicotinic acetylcholine receptors might prove useful in the therapy of cannabinoid dependence. Research by Steven R. Goldberg has significantly contributed to the progress in this research field.

Preclinical studies on the reinforcing effects of cannabinoids. A tribute to the scientific research of Dr. Steve Goldberg

RATIONALE

The reinforcing effects of most abused drugs have been consistently demonstrated and studied in animal models, although those of marijuana were not, until the demonstration 15 years ago that delta-9-tetrahydrocannabinol (THC) could serve as a reinforcer in self-administration (SA) procedures in squirrel monkeys. Until then, those effects were inferred using indirect assessments.

OBJECTIVES

The aim of this manuscript is to review the primary preclinical procedures used to indirectly and directly infer reinforcing effects of cannabinoid drugs.

METHODS

Results will be reviewed from studies of cannabinoid discrimination, intracranial self-stimulation (ICSS), conditioned place preference (CPP), as well as change in levels of dopamine assessed in brain areas related to reinforcement, and finally from self-administration procedures. For each procedure, an evaluation will be made of the predictive validity in detecting the potential abuse liability of cannabinoids based on seminal papers, with the addition of selected reports from more recent years especially those from Dr. Goldberg's research group.

RESULTS AND CONCLUSIONS

ICSS and CPP do not provide consistent results for the assessment of potential for abuse of cannabinoids. However, drug discrimination and neurochemistry procedures appear to detect potential for abuse of cannabinoids, as well as several novel "designer cannabinoid drugs." Though after 15 years transfer of the self-administration model of marijuana abuse from squirrel monkeys to other species remains somewhat problematic, studies with the former species have substantially advanced the field, and several reports have been published with consistent self-administration of cannabinoid agonists in rodents.

Keep off the grass? Cannabis, cognition and addiction

In an increasing number of states and countries, cannabis now stands poised to join alcohol and tobacco as a legal drug. Quantifying the relative adverse and beneficial effects of cannabis and its constituent cannabinoids should therefore be prioritized. Whereas newspaper headlines have focused on links between cannabis and psychosis, less attention has been paid to the much more common problem of cannabis addiction. Certain cognitive changes have also been attributed to cannabis use, although their causality and longevity are fiercely debated. Identifying why some individuals are more vulnerable than others to the adverse effects of cannabis is now of paramount importance to public health. Here, we review the current state of knowledge about such vulnerability factors, the variations in types of cannabis, and the relationship between these and cognition and addiction.

Involvement of opioid system in cognitive deficits induced by ∆⁹-tetrahydrocannabinol in rats

RATIONALE

Cannabis is a widely used illicit substance. ∆(9)-Tetrahydrocannabinol (THC), the major psychoactive component of cannabis, is known to induce cognitive deficits that closely resemble the impairment observed in schizophrenic patients. We previously reported that THC (6 mg/kg) impairs spatial memory in the eight-arm radial maze, and that this memory disturbance was reversed by the cannabinoid CB(1) receptor antagonist rimonabant (0.1 mg/kg), suggesting that the effect of THC is mediated through cannabinoid CB(1) receptors.

OBJECTIVES

The present study was designed to examine the possible involvement of opioid receptors in the THC-induced impairment of spatial memory.

METHODS

The effects of treatment with the nonselective opioid receptor antagonist naloxone (0.3 and 1 mg/kg), the μ-opioid receptor antagonist β-funaltrexamine (0.3 and 1 mg/kg), the δ-opioid receptor antagonist naltrindole (1 and 3 mg/kg), and the κ-opioid receptor antagonist nor-binaltorphimine (0.03 and 0.1 mg/kg) on the impairment of spatial memory induced by THC were evaluated using the eight-arm radial maze.

RESULTS

The nonselective opioid receptor antagonist naloxone, the μ-opioid receptor antagonist β-funaltrexamine, and the κ-opioid receptor antagonist nor-binaltorphimine, but not the δ-opioid receptor antagonist naltrindole, attenuated THC-induced cognitive deficits, suggesting an involvement of μ- and κ-opioid receptors in this behavioral response.

CONCLUSIONS

These results demonstrate that the endogenous opioid system is involved in the regulation of the acute short-term and working memory deficits induced by cannabis.

Cannabinoid receptor stimulation increases motivation for nicotine and nicotine seeking

The cannabinoid system appears to play a critical facilitative role in mediating the reinforcing effects of nicotine and relapse to nicotine-seeking behaviour in abstinent subjects based on the actions of cannabinoid (CB) receptor antagonists. However, the effects of CB receptor stimulation on nicotine self-administration and reinstatement have not been systematically studied. Here, we studied the effects of WIN 55,212-2, a CB1/2 agonist, on intravenous nicotine self-administration under fixed-ratio (FR) and progressive-ratio (PR) schedules of reinforcement in rats. The effects of WIN 55,212-2 on responding for food under similar schedules were also studied. In addition, the effects of WIN 55,212-2 on nicotine- and cue-induced reinstatement of nicotine seeking were also studied, as well as the effects of WIN 55,212-2 on nicotine discrimination. WIN 55,212-2 decreased nicotine self-administration under the FR schedule. However, co-administration of WIN 55,212-2 with nicotine decreased responding for food, which suggests that this effect was non-selective. In contrast, WIN 55,212-2 increased both nicotine self-administration and responding for food under the PR schedule, produced dose-dependent reinstatement of nicotine seeking, and enhanced the reinstatement effects of nicotine-associated cues. Some of these effects were reversed by the CB1 antagonist rimonabant, but not by the CB2 antagonist AM630. In the drug discrimination tests between saline and 0.4 mg/kg nicotine, WIN 55,212-2 produced no nicotine-like discriminative effects but significantly potentiated discriminative stimulus effects of nicotine at the low dose through a CB1-receptor-dependent mechanism. These findings indicate that cannabinoid CB1-receptor stimulation increases the reinforcing effects of nicotine and precipitates relapse to nicotine-seeking behaviour in abstinent subjects. Thus, modulating CB1-receptor signalling might have therapeutic value for treating nicotine dependence.

The pharmacology of the endocannabinoid system: functional and structural interactions with other neurotransmitter systems and their repercussions in behavioral addiction

Addiction is a chronic, recurring and complex disorder. It is characterized by anomalous behaviors that are linked to permanent or long-lasting neurobiological alterations. Furthermore, the endocannabinoid system has a crucial role in mediating neurotransmitter release as one of the main neuromodulators of the mammalian central nervous system. The purpose of the present review is to instruct readers about the functional and structural interactions between the endocannabinoid system and the main neurotransmitter systems of the central nervous system in the context of drug addiction. With this aim, we have systematically reviewed the main findings of most of the existing literature that explores cross-talk in the five brain areas that are most traditionally implicated in addiction: amygdala, prefrontal cortex, nucleus accumbens, hippocampus and ventral tegmental area (VTA). The neurotransmission systems influenced by the pharmacology of the endocannabinoid system in these brain areas, which are reviewed here, are gamma-aminobutyric acid (GABA), glutamate, the main biogenic amines (dopamine, noradrenaline and serotonin), acetylcholine and opioids. We show that all of these neurotransmitter systems can be modulated differentially in each brain area by the activation or deactivation of cannabinoid CB1 brain receptors. Specifically, most of the studies relate to the hippocampus and nucleus accumbens. Moreover, the neurotransmitter with the fewest number of related studies is acetylcholine (excepting in the hippocampus), whereas there is a large number that evaluates GABA, glutamate and dopamine. Finally, we propose a possible interpretation of the role of the endocannabinoid system in the phenomenon of addiction.

Ligands that target cannabinoid receptors in the brain: from THC to anandamide and beyond

A major finding--that (-)-trans-Delta(9)-tetrahydrocannabinol (Delta(9)-THC) is largely responsible for the psychotropic effects of cannabis--prompted research in the 1970s and 1980s that led to the discovery that this plant cannabinoid acts through at least two types of cannabinoid receptor, CB(1) and CB(2), and that Delta(9)-THC and other compounds that target either or both of these receptors as agonists or antagonists have important therapeutic applications. It also led to the discovery that mammalian tissues can themselves synthesize and release agonists for cannabinoid receptors, the first of these to be discovered being arachidonoylethanolamide (anandamide) and 2-arachidonoylglycerol. These 'endocannabinoids' are released onto their receptors in a manner that appears to maintain homeostasis within the central nervous system and sometimes either to oppose or to mediate or exacerbate the unwanted effects of certain disorders. This review provides an overview of the pharmacology of cannabinoid receptors and their ligands. It also describes actual and potential clinical uses both for cannabinoid receptor agonists and antagonists and for compounds that affect the activation of cannabinoid receptors less directly, for example by inhibiting the enzymatic hydrolysis of endocannabinoids following their release.

Cannabis and psychiatric disorders: it is not only addiction

Since the discovery of the endocannabinoid system, a growing body of psychiatric research has emerged focusing on the role of this system in major psychiatric disorders like schizophrenia (SCZ), bipolar disorder (BD), major depression and anxiety disorder. Continuing in the line of earlier epidemiological studies, recent replication studies indicate that frequent cannabis use doubles the risk for psychotic symptoms and SCZ. Further points of clinical research interest are alterations of endocannabinoids and their relation to symptoms as well as postmortem analyses of cannabinoid CB(1) receptor densities in SCZ. A possible neurobiological mechanism for the deleterious influence of cannabis use in SCZ has been suggested, involving the disruption of endogenous cannabinoid signaling and functioning. Even though the number of studies is still limited for affective and anxiety disorders, previous results suggest these diseases to be exciting objectives of cannabinoid-associated research. Therefore, it became apparent that cannabis use is not only frequent in patients suffering from BD, but that it also induces manic symptoms in this group. In addition, prior antipsychotic treatment decreased the numerical density of CB(1) immunoreactive glial cells in bipolar patients. Although the data on the influence of cannabis use on the development of major depression is controversial, cannabinoid compounds could display a new class of medication, as suggested by the antidepressive effects of the fatty acid amino hydrolase inhibitor URB597 in animal models. With numerous open questions and controversial results, further research is required to specify and extend the findings in this area, which provides a promising target for novel pharmacotherapeutic interventions.

Endogenous opiates and behavior: 2006

This paper is the 29th consecutive installment of the annual review of research concerning the endogenous opioid system, now spanning 30 years of research. It summarizes papers published during 2006 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurological disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration and thermoregulation (Section 16); and immunological responses (Section 17).

The diverse CB1 and CB2 receptor pharmacology of three plant cannabinoids: delta9-tetrahydrocannabinol, cannabidiol and delta9-tetrahydrocannabivarin

Cannabis sativa is the source of a unique set of compounds known collectively as plant cannabinoids or phytocannabinoids. This review focuses on the manner with which three of these compounds, (-)-trans-delta9-tetrahydrocannabinol (delta9-THC), (-)-cannabidiol (CBD) and (-)-trans-delta9-tetrahydrocannabivarin (delta9-THCV), interact with cannabinoid CB1 and CB2 receptors. Delta9-THC, the main psychotropic constituent of cannabis, is a CB1 and CB2 receptor partial agonist and in line with classical pharmacology, the responses it elicits appear to be strongly influenced both by the expression level and signalling efficiency of cannabinoid receptors and by ongoing endogenous cannabinoid release. CBD displays unexpectedly high potency as an antagonist of CB1/CB2 receptor agonists in CB1- and CB2-expressing cells or tissues, the manner with which it interacts with CB2 receptors providing a possible explanation for its ability to inhibit evoked immune cell migration. Delta9-THCV behaves as a potent CB2 receptor partial agonist in vitro. In contrast, it antagonizes cannabinoid receptor agonists in CB1-expressing tissues. This it does with relatively high potency and in a manner that is both tissue and ligand dependent. Delta9-THCV also interacts with CB1 receptors when administered in vivo, behaving either as a CB1 antagonist or, at higher doses, as a CB1 receptor agonist. Brief mention is also made in this review, first of the production by delta9-THC of pharmacodynamic tolerance, second of current knowledge about the extent to which delta9-THC, CBD and delta9-THCV interact with pharmacological targets other than CB1 or CB2 receptors, and third of actual and potential therapeutic applications for each of these cannabinoids.

Supraspinal modulation of pain by cannabinoids: the role of GABA and glutamate

Recent physiological, pharmacological and anatomical studies provide evidence that one of the main roles of the endocannabinoid system in the brain is the regulation of gamma-aminobutyric acid (GABA) and glutamate release. This article aims to review this evidence in the context of its implications for pain. We first provide a brief overview of supraspinal regulation of nociception, followed by a review of the evidence that the brain's endocannabinoid system modulates nociception. We look in detail at regulation of supraspinal GABAergic and glutamatergic neurons by the endocannabinoid system and by exogenously administered cannabinoids. Finally, we review the evidence that cannabinoid-mediated modulation of pain involves modulation of GABAergic and glutamatergic neurotransmission in key brain regions.

Nicotinic alpha 7 receptors as a new target for treatment of cannabis abuse

Increasing use of cannabis makes the search for medications to reduce cannabis abuse extremely important. Here, we show that homomeric alpha7 nicotinic receptors are novel molecular entities that could be targeted in the development of new drugs for the treatment of cannabis dependence. In rats, systemic administration of the selective alpha7 nicotinic acetylcholine receptor antagonist methyllycaconitine (MLA), but not the selective heteromeric non-alpha7 nicotinic acetylcholine receptor antagonist dihydrobetaerythroidine, (1) antagonized the discriminative effects of delta-9-tetrahydrocannabinol (THC), the main active ingredient in cannabis, (2) reduced intravenous self-administration of the synthetic cannabinoid CB1 receptor agonist WIN55,212-2 [(R)-(+)-[2,3-dihydro-5-methyl-3[(4-morpholinyl)methyl]pyrrolo[1,2,3-de]-1,4-benzoxazinyl]-(1-naphthalenyl)methanone, mesylate salt], and (3) decreased THC-induced dopamine elevations in the shell of the nucleus accumbens. Altogether, our results indicate that blockade of alpha7 nicotinic receptors reverses abuse-related behavioral and neurochemical effects of cannabinoids. Importantly, MLA reversed the effects of cannabinoids at doses that did not produce depressant or toxic effects, further pointing to alpha7 nicotinic antagonists as potentially useful agents in the treatment of cannabis abuse in humans.

Nicotinic Facilitation of Δ9-Tetrahydrocannabinol Discrimination Involves Endogenous Anandamide

Systemic administration of the main active ingredient in cannabis, Delta9-tetrahydrocannabinol (THC), alters extracellular levels of acetylcholine in several brain areas, suggesting an involvement of the cholinergic system in the psychotropic effects of cannabis. Here, we investigated whether drugs acting at either nicotinic or muscarinic receptors can modulate the discriminative effects of THC. In rats that had learned to discriminate effects of 3 mg/kg i.p. injections of THC from injections of vehicle, the nicotinic agonist nicotine (0.1-0.56 mg/kg subcutaneous) and the muscarinic agonist pilocarpine (0.3-3 mg/kg i.p.) did not produce THC-like effects, but they both potentiated the discriminative effects of low doses of THC (0.3-1 mg/kg). Neither the nicotinic antagonist mecamylamine (1-5.6 mg/kg i.p.) nor the muscarinic antagonist scopolamine (0.01-0.1 mg/kg i.p.) altered the discriminative effects of THC, but they blocked the potentiation of discriminative effects of THC by nicotine and pilocarpine, respectively. The cannabinoid CB(1) antagonist rimonabant (1 mg/kg i.p.) reversed nicotine- but not pilocarpine-induced potentiation of THC discrimination, suggesting that nicotine potentiation is, at least in part, mediated by release of endogenous cannabinoids in the brain. In addition, when metabolic degradation of the endogenous cannabinoid anandamide was blocked by the fatty acid amide hydrolase inhibitor cyclohexyl carbamic acid 3'-carbamoylbiphenil-3-yl-ester (URB-597; 0.3 mg/kg i.p.) nicotine, but not pilocarpine, produced significant THC-like discriminative effects that were antagonized by rimonabant. Our results suggest that nicotinic and muscarinic cholinergic receptors modulate the discriminative effects of THC by fundamentally different mechanisms. Nicotinic, but not muscarinic, modulation of THC discrimination involves elevations in endogenous levels of anandamide.

Cannabis and psychosis: an update on course and biological plausible mechanisms

PURPOSE OF REVIEW

Cannabis use is the most commonly abused illicit substance. Its relation with psychosis remains a topic of debate. Epidemiological studies suggest that cannabis is a component cause accounting for approximately 10% of cases. An increasing number of studies have been published on neurobiological effects of cannabis and vulnerability of psychosis.

RECENT FINDINGS

Acute cannabis administration can induce memory impairments, sometimes persisting months following abstinence. There is no evidence that residual effects on cognition remain after years of abstinence. The scarce literature on neuro-imaging mainly done in nonpsychotic populations, show little evidence that cannabis has effects on brain anatomy. Acute effects of cannabis include increases of cerebral blood flow, whereas long-term effects of cannabis include attenuation of cerebral blood flow. In animals Delta9-tetrahydrocannabinol enhances dopaminergic neurotransmission in brain regions known to be implicated in psychosis. Studies in humans show that genetic vulnerability may add to increased risk of developing psychosis and cognitive impairments following cannabis consumption. Delta9-tetrahydrocannabinol induces psychotic like states and memory impairments in healthy volunteers.

SUMMARY

Simultaneously with increasing understanding of neurobiological cannabis effects, there is a lack of studies in people with psychosis. There are plausible mechanisms that might explain the psychotogenic effects of cannabis.

Cannabinoids reveal importance of spike timing coordination in hippocampal function

Cannabinoids impair hippocampus-dependent memory in both humans and animals, but the network mechanisms responsible for this effect are unknown. Here we show that the cannabinoids Delta(9)-tetrahydrocannabinol and CP55940 decreased the power of theta, gamma and ripple oscillations in the hippocampus of head-restrained and freely moving rats. These effects were blocked by a CB1 antagonist. The decrease in theta power correlated with memory impairment in a hippocampus-dependent task. By simultaneously recording from large populations of single units, we found that CP55940 severely disrupted the temporal coordination of cell assemblies in short time windows (<100 ms) yet only marginally affected population firing rates of pyramidal cells and interneurons. The decreased power of local field potential oscillations correlated with reduced temporal synchrony but not with firing rate changes. We hypothesize that reduced spike timing coordination and the associated impairment of physiological oscillations are responsible for cannabinoid-induced memory deficits.