Analysis of tolerance and behavioral/physical dependence during chronic CB1 agonist treatment: effects of CB1 agonists, antagonists, and noncannabinoid drugs

Chronic exposure to inhaled vaporized cannabis high in Δ9-THC suppresses Adderall-induced brain activity

Background

There are increasing reports of the misuse of prescription psychostimulants for cognitive enhancement together with recreational cannabis. This raises a concern that chronic use of cannabis high in Δ9-THC may alter the sensitivity to amphetamines. In this exploratory study we hypothesized chronic exposure to Δ9-THC through vaporized cannabis would diminish the central nervous system (CNS) activity of Adderall.

Methods

To address this issue we exposed male and female mice to inhaled vaporized cannabis (10.3% Δ9-THC) or placebo for 30 min each day for ten consecutive days. After 24 h, mice were imaged fully awake for changes in BOLD signal following an IP injection of Adderall (60 µg) during the scanning session. After a 2-week washout, without any cannabis or placebo exposure, mice were again imaged and challenged with Adderall during the scanning session. The data were registered to a mouse 3D MRI atlas with 134 brain regions providing site-specific increases and decreases in global brain activity.

Results

Mice exposed to cannabis when compared to placebo showed a decrease in brain activation to Adderall. The blunted Adderall response was characterized by a decrease in positive BOLD signal and increase in negative BOLD. The prefrontal cortex, accumbens, ventral pallidum, caudate/putamen, and thalamus were most affected. After a 2-week wash out there were no significant differences between the cannabis and placebo groups when challenged with Adderall.

Summary

This exploratory study shows that short, daily exposures to inhaled cannabis, something equivalent to recreational use, affects the sensitivity to the psychostimulant Adderall. The reduced Adderall effect on brain activity, particularly circuitry associated with dopaminergic signaling raises concerns about escalation in psychostimulant use.

Cannabinoid hyperemesis syndrome: prevalence and management in an era of cannabis legalization

As more states legalize cannabinoid products for recreational use and medicinal purposes, the prevalence of cannabinoid hyperemesis syndrome has become increasingly common. Yet, it remains unrecognized to many healthcare providers along with the most efficacious treatments. Cannabinoid hyperemesis syndrome most often presents with episodic vomiting secondary to chronic daily cannabis use over several months to years. Patients often complain of nausea and abdominal pain that is improved by taking hot showers or baths. Symptoms are alleviated with the cessation of cannabis use over a period of 6-12 months. Treatment for acute attacks often consists of parenteral benzodiazepines in the inpatient setting. Long-term management and prevention of further attacks are aided by tricyclic antidepressants such as amitriptyline with a dose range of 50-200 mg/d. Once a patient is in remission, amitriptyline can be tapered slowly. As cannabis becomes more widely available and accepted in the continental United States, so must education on the diagnosis of cannabinoid hyperemesis syndrome and treatment strategies.

Effects of cannabinoid agonists and antagonists in male rats discriminating the synthetic cannabinoid AM2201

The synthetic forms of delta-9-tetrahydrocannabinol (Δ9-THC), dronabinol or nabilone, have been approved to treat several indications. However, due to safety concerns their clinical utility remains limited. Consequently, there is a need for developing cannabinoid (CB) ligands that display better behavioral pharmacological profiles than Δ9-THC. Here, we utilized drug discrimination methods to compare the interoceptive effects of CB ligands that vary in potency, efficacy, and selectivity at the CB receptors, including two ligands, AM411 and AM4089, that show CB1 partial agonist-like actions in vitro. Male rats were trained to discriminate 0.1 mg/kg AM2201 from saline under a fixed-ratio (FR) 10 response schedule of food reinforcement. After establishing AM2201's discriminative-stimulus effects, pretreatment tests with the CB1 antagonist/inverse agonist rimonabant blocked AM2201's effects, whereas the peripherally-restricted antagonist AM6545 had no effect. Next, the generalization profiles of AM411 and AM4089 with CB1 full agonists (JWH-018, CP-55,940, AM8936), partial agonist (Δ9-THC), and non-cannabinoids (fentanyl, atropine) were compared. The CBs either fully (AM2201, CP-55,940, JWH-018, AM8936, Δ9-THC) or partially (AM411, AM4089) substituted for AM2201, whereas fentanyl and atropine did not produce AM2201-like effects. All CB drugs were more potent than Δ9-THC and correlation analysis confirmed that the relative behavioral potencies of CBs corresponded strongly with their relative affinities at the CB1 but not CB2 receptors. Together, our results further demonstrate that AM411 and AM4089 exhibit better pharmacological profiles compared to Δ9-THC, in that they are more potent and display in vivo partial agonist-like actions that are centrally mediated via CB1 receptors.

Hexahydrocannabinol Pharmacology, Toxicology, and Analysis: The First Evidence for a Recent New Psychoactive Substance

BACKGROUND

During the last two years, hexahydrocannabinol (HHC), the hydrogenated derivative of tetrahydrocannabinol has been freely sold by internet websites as a "legal" replacement to THC and cannabis in a range of highly attractive branded and unbranded products, some of which are sold as "legal highs". Potentially, there could be a large demand for HHC products by individuals in Europe and internationally.

METHODS

Studies reporting HHC pharmacology, toxicology and analysis were identified from Pubmed and Scopus databases, and official international organizations' websites were considered.

RESULTS

HHC showed the effects of the typical cannabinoid on the central nervous system, with lower potency than Δ9-THC. A few studies highlighted that 9(R)-HHC is more potent than 9(S)-HHC. This molecule showed an affinity for cannabinoid receptor CB1 both in vitro and in vivo, suggesting a possible therapeutic effect in several pathologies. However, the affinity for the CB1 receptor suggests a possible addiction potential, inducing the users to misuse it. Since actual intoxication cases have not yet been reported, the HHC harmful potential was not described, probably due to the lack of effective analytical methods to detect HHC in biological matrices. Conversely, different analytical assays were developed and validated to separate HHC epimers in natural and non-natural sources.

CONCLUSION

Similarly to other NPS, the HHC represents a cheaper alternative to the controlled Δ9-THC. Its monitoring is a crucial challenge for toxicological and forensic purposes. To this concern, it is essential to further investigate HHC to support health providers in the identification of related intoxications.

Effects of the cannabinoid CB1-receptor neutral antagonist AM4113 and antagonist/inverse agonist rimonabant on fentanyl discrimination in male rats

Evidence suggests the existence of a functional interaction between endogenous cannabinoid (CB) and opioid systems. Thus, targeting CB₁ receptors might be a viable approach to develop new medications for opioid use disorders (OUD). The present studies were undertaken to evaluate the effects of the neutral CB₁ antagonist AM4113 and the CB₁ antagonist/inverse agonist rimonabant in male rats trained to discriminate 0.032 mg/kg fentanyl from saline under a 10-response fixed-ratio (FR-10) schedule of food reinforcement. Results show that the µ-opioid agonists (fentanyl, oxycodone, and morphine) substituted fully and dose-dependently for fentanyl, whereas pretreatment with the µ-opioid antagonist naltrexone antagonized fentanyl's discriminative-stimulus effects. In interaction studies, AM4113 (0.32 or 1.0 mg/kg) was more effective in blocking fentanyl discrimination at 10-fold lower doses that did not modify rates of food-maintained responding, whereas rimonabant (1.0-10 mg/kg) produced some attenuation of fentanyl's discriminative-stimulus effects at the highest dose tested which also significantly decreased response rates. These results extend our recent work showing that AM4113 can effectively block the behavioral effects of heroin without producing rimonabant-like adverse effects. Taken together, these data suggests that CB₁ neutral antagonists effectively block the behavioral effects of structurally distinct morphinan (heroin) and phenylpiperidine-based (fentanyl) opioids and may provide a novel therapeutic option for the treatment of OUD.

Endocannabinoid system and cannabis hyperemesis syndrome: a narrative update

Cannabis use has been increasing in the United States and throughout the world. It is derived from one of the earliest plants cultivated by humans - Cannabis sativa. Cannabis (also called marijuana) is the most commonly used psychoactive substance worldwide. The cannabis plant has more than 400 chemicals, of which more than 100 cannabinoids (such as cannabigerol, cannabidiol, and cannabinol) have been identified. The endocannabinoid system (ECS) plays an essential role in the effects of cannabis on end organs. Although cannabis use has been reported for many decades, some of its unique adverse effects of nausea, vomiting, and abdominal pain, termed as cannabis hyperemesis syndrome (CHS), were noted recently. The legal status of cannabis in the United States has been rapidly changing from state to state. The incidence of CHS is expected to rise with rising access to cannabis in the United States. Furthermore, CHS is frequently underdiagnosed due to a lack of uniform criteria, subjective nature of symptoms, and overlap with cyclical vomiting syndrome (CVS). Understanding the ECS and its role in biphasic response (proemetic and antiemetic) of CHS is critical to explain its pathophysiology. As the use of cannabis increases globally, awareness of CHS is warranted for early recognition and prompt treatment to avoid complications. We describe the putative mechanism of CHS with an overview of the clinical features in these patients. Furthermore, we highlight the differences between CHS and CVS with important differentials to consider. We provide a narrative update on the current evidence on CHS pathophysiology, diagnosis, treatment, and identifying research gaps.

Effects of cannabinoid exposure on short-term memory and medial orbitofrontal cortex function and chemistry in adolescent female rhesus macaques

Aim

There is increasing concern that cannabinoid exposure during adolescence may disturb brain maturation and produce long-term cognitive deficits. However, studies in human subjects have provided limited evidence for such causality. The present study utilized behavioral and neuroimaging endpoints in female non-human primates to examine the effects of acute and chronic exposure during adolescence to the cannabinoid receptor full agonist, AM2389, on cognitive processing and brain function and chemistry.

Materials and methods

Adolescent female rhesus macaques were trained on a titrating-delay matching-to-sample (TDMTS) touchscreen task that assays working memory. TDMTS performance was assessed before and during chronic exposure to AM2389, following antagonist (rimonabant) administration, and after discontinuation of the chronic regimen. Resting-state fMRI connectivity and magnetic resonance spectroscopy data were acquired prior to drug treatment, during chronic exposure, and following its discontinuation. Voxels were placed in the medial orbitofrontal cortex (mOFC), a region involved in memory processing that undergoes maturation during adolescence.

Results

TDMTS performance was dose-dependently disrupted by acute AM2389; however, chronic treatment resulted in tolerance to these effects. TDMTS performance also was disrupted by discontinuation of the chronic regimen but surprisingly, not by rimonabant administration during chronic AM2389 treatment. mOFC N-acetylaspartate/creatine ratio decreased after acute and chronic administration but returned to baseline values following discontinuation of chronic treatment. Finally, intra-network functional connectivity (mOFC) increased during the chronic regimen and returned to baseline values following its discontinuation.

Conclusion

Neural effects of a cannabinergic drug may persist during chronic exposure, notwithstanding the development of tolerance to behavioral effects. However, such effects dissipate upon discontinuation, reflecting the restorative capacity of affected brain processes.

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

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

Oxa-adamantyl cannabinoids

As a continuation of earlier work on classical cannabinoids bearing bulky side chains we report here the design, synthesis, and biological evaluation of 3'-functionalized oxa-adamantyl cannabinoids as a novel class of cannabinergic ligands. Key synthetic steps involve nucleophilic addition/transannular cyclization of aryllithium to epoxyketone in the presence of cerium chloride and stereoselective construction of the tricyclic cannabinoid nucleus. The synthesis of the oxa-adamantyl cannabinoids is convenient, and amenable to scale up allowing the preparation of these analogs in sufficient quantities for detailed in vitro evaluation. The novel oxa-adamantyl cannabinoids reported here were found to be high affinity ligands for the CB1 and CB2 cannabinoid receptors. In the cyclase assay these compounds were found to behave as potent and efficacious CB1 receptor agonists. Isothiocyanate analog AM10504 is capable of irreversibly labeling both the CB1 and CB2 receptors.

Cannabis hyperemesis syndrome: an update on the pathophysiology and management

Cannabis hyperemesis syndrome (CHS) is a form of functional gut-brain axis disorder characterized by bouts of episodic nausea and vomiting worsened by cannabis intake. It is considered as a variant of cyclical vomiting syndrome seen in cannabis users especially characterized by compulsive hot bathing/showers to relieve the symptoms. CHS was reported for the first time in 2004, and since then, an increasing number of cases have been reported. With cannabis use increasing throughout the world as the threshold for legalization becomes lower, its user numbers are expected to rise over time. Despite this trend, a strict criterion for the diagnosis of CHS is lacking. Early recognition of CHS is essential to prevent complications related to severe volume depletion. The recent body of research recognizes that patients with CHS impose a burden on the healthcare systems. Understanding the pathophysiology of the endocannabinoid system (ECS) remains central in explaining the clinical features and potential drug targets for the treatment of CHS. The frequency and prevalence of CHS change in accordance with the doses of tetrahydrocannabinol and other cannabinoids in various formulations of cannabis. CHS is unique in presentation, because of the cannabis’s biphasic effect as anti-emetic at low doses and pro-emetic at higher doses, and the association with pathological hot water bathing. In this narrative review, we elaborate on the role of the ECS, its management, and the identification of gaps in our current knowledge of CHS to further enhance its understanding in the future.

Cannabinoid hyperemesis syndrome: definition, pathophysiology, clinical spectrum, insights into acute and long-term management

Although cannabinoid hyperemesis syndrome (CHS) was first reported more than 15 years ago, it still remains an unfamiliar clinical entity among physicians worldwide. CHS is categorized by Rome IV classification as a functional gastroduodenal disorder. It is characterized by stereotypical episodic vomiting in the setting of chronic, daily cannabis use, with cycles decreasing by the cessation of cannabis. CHS is also associated with abdominal pain reduced by hot baths and showers with comparative well-being between attacks. Thus, its clinical presentation resembles 'classic' cyclic vomiting syndrome, but eliciting a cannabis history is crucial in diagnosing this entity. In acute attacks, parenteral benzodiazepines are very effective. For prevention and long-term management, tricyclic antidepressants such as amitriptyline are the mainstay of therapy requiring doses in the range of 50-200 mg/d to achieve symptom control. In addition, counseling to achieve marijuana cessation, accompanied by antianxiety medications, is necessary for sustaining clinical outcomes. Once the patient is in remission and off marijuana for a period of 6-12 months, then tapering the dose of amitriptyline can be implemented, with the goal of no therapy being achieved in the majority of patients over time. With the legalization of marijuana in many states, CHS will become an increasingly prevalent clinical entity, so educating about CHS is an important goal, particularly for emergency department physicians who generally first encounter these patients.

Antiemetic Effects of Cannabinoid Agonists in Nonhuman Primates

Attenuating emesis elicited by both disease and medical treatments of disease remains a critical public health challenge. Although cannabinergic medications have been used in certain treatment-resistant populations, Food and Drug Administration-approved cannabinoid antiemetics are associated with undesirable side effects, including cognitive disruption, that limit their prescription. Previous studies have shown that a metabolically stable analog of the endocannabinoid anandamide, methanandamide (mAEA), may produce lesser cognitive disruption than that associated with the primary psychoactive constituent in cannabis, Δ9-tetrahydrocannabinol (Δ9-THC), raising the possibility that endocannabinoids may offer a therapeutic advantage over currently used medications. The present studies were conducted to evaluate this possibility by comparing the antiemetic effects of Δ9-THC (0.032-0.1 mg/kg) and mAEA (3.2-10.0 mg/kg) against nicotine- and lithium chloride (LiCl)-induced emesis and prodromal hypersalivation in squirrel monkeys. Pretreatment with 0.1 mg/kg Δ9-THC blocked nicotine-induced emesis and reduced hypersalivation in all subjects and blocked LiCl-induced emesis and reduced hypersalivation in three of four subjects. Pretreatment with 10 mg/kg mAEA blocked nicotine-induced emesis in three of four subjects and LiCl-induced emesis in one of four subjects and reduced both nicotine- and LiCl-induced hypersalivation. Antiemetic effects of Δ9-THC and mAEA were reversed by rimonabant pretreatment, providing verification of cannabinoid receptor type 1 mediation. These studies systematically demonstrate for the first time the antiemetic effects of cannabinoid agonists in nonhuman primates. Importantly, although Δ9-THC produced superior antiemetic effects, the milder cognitive effects of mAEA demonstrated in previous studies suggest that it may provide a favorable treatment option under clinical circumstances in which antiemetic efficacy must be balanced against side effect liability. SIGNIFICANCE STATEMENT: Emesis has significant evolutionary value as a defense mechanism against ingested toxins; however, it is also one of the most common adverse symptoms associated with both disease and medical treatments of disease. The development of improved antiemetic pharmacotherapies has been impeded by a paucity of animal models. The present studies systematically demonstrate for the first time the antiemetic effects of the phytocannabinoid Δ9-tetrahydrocannabinol and endocannabinoid analog methanandamide in nonhuman primates.

Anticonvulsant and Neuroprotective Effects of Cannabidiol During the Juvenile Period

Anticonvulsant effects of cannabidiol (CBD), a nonpsychoactive cannabinoid, have not been investigated in the juvenile brain. We hypothesized that CBD would attenuate epileptiform activity at an age when the brain first becomes vulnerable to neurotoxicity and social/cognitive impairments. To induce seizures, kainic acid (KA) was injected either into the hippocampus (KAih) or systemically (KAip) on postnatal (P) day 20. CBD was coadministered (KA + CBDih, KA + CBDip) or injected 30 minutes postseizure onset (KA/CBDih, KA/CBDip). Hyperactivity, clonic convulsions, and electroencephalogram rhythmic oscillations were attenuated or absent after KA + CBDih and reduced after KA + CBDip. NeuN immunohistochemistry revealed neuroprotection. Augmented reactive glia number and expression were reversed in CA1 but persisted deep within the dentate hilus. Parvalbumin-positive (PV+) interneurons were reduced in both models, whereas immunolabeling was dramatically increased within ipsilateral and contralateral dendritic/neuropilar fields following KA + CBDih. Cannabinoid receptor 1 (CB1) expression was minimally affected after KAih contrasting elevations observed after KAip. Intracranial coadministration data suggest that CBD has higher efficacy in epilepsy with hippocampal focus rather than when extrahippocampal amygdala/cortical structures are triggered by systemic treatments. Inhibition of surviving PV+ and CB1+ interneurons may be facilitated by CBD implying a protective role in regulating hippocampal seizures and neurotoxicity at juvenile ages.

Tolerance and dependence to Δ9-tetrahydrocannabinol in rhesus monkeys: Activity assessments

Cannabis withdrawal upon discontinuation of long-term, heavy Cannabis use is reported in humans; however, methods to establish the nature and intensity of cannabinoid withdrawal, especially directly observable signs, have not been widely established. This study quantified activity in the home cage of rhesus monkeys and examined the extent to which activity can be used to quantify tolerance to and dependence on Δ9-tetrahydrocannabinol (Δ9-THC). Home-cage activity was measured in one group that received Δ9-THC (1 mg/kg s.c.) every 12 h (i.e., chronic Δ9-THC), and a second group that received Δ9-THC (0.1 mg/kg i.v.) once every 3 days (i.e., intermittent Δ9-THC). Treatment was temporarily discontinued in the chronic Δ9-THC group and the effects of rimonabant and Δ9-THC were examined in both groups. Activity counts were highest during the day (lights on 0600-2000 h) and were lower at night. Rimonabant (0.1-3.2 mg/kg i.v.) dose-dependently increased activity (maximum 20-fold) in the chronic Δ9-THC group but did not significantly alter activity in the intermittent Δ9-THC group. Δ9-THC (0.32-3.2 mg/kg i.v.) dose-dependently decreased activity counts (maximum 4-fold) in both groups but was somewhat more potent in the intermittent as compared with the Δ9-THC group. Discontinuation of Δ9-THC treatment resulted in an immediate (i.e., within 24 h) and time-related increase in activity. The time-related increase in home-cage activity upon abrupt discontinuation of chronic Δ9-THC treatment, as well as the effects of rimonabant to increase activity in monkeys receiving chronic, but not intermittent, Δ9-THC treatment, are consistent with signs of physical dependence on Δ9-THC in primates.

Potential Mechanisms Underlying the Deleterious Effects of Synthetic Cannabinoids Found in Spice/K2 Products

The chief psychoactive constituent of many bioactive phytocannabinoids (Δ⁹-tetrahydrocannabinol, Δ⁹-THC) found in hemp, cannabis or marijuana plants are scientifically denoted by the Latin term, Cannabis sativa, acts on cell surface receptors. These receptors are ubiquitously expressed. To date, two cannabinoid receptors have been cloned and characterized. Cannabinoid receptor type 1 (CB1R) is found to serve as the archetype for cannabinoid action in the brain. They have attracted wide interest as the mediator of all psychoactive properties of exogenous and endogenous cannabinoids and they are abundantly expressed on most inhibitory and excitatory neurons. Recent evidence established that cannabinoid receptor type 2 (CB2R) is also expressed in the neurons at both presynaptic and postsynaptic terminals and are involved in neuropsychiatric effects. Distinct types of cells in many regions in the brain express CB2Rs and the cellular origin of CB2Rs that induce specific behavioral effects are emerging. To mimic the bliss effects of marijuana, synthetic cannabinoids (SCBs) have been sprayed onto plant material, and this plant material has been consequently packaged and sold under brand name “Spice” or “K2”. These SCBs have been shown to maintain their affinity and functional activity for CB1R and CB2R and have been shown to cause severe harmful effects when compared to the effects of Δ⁹-THC. The present review discusses the potential brain mechanisms that are involved in the deleterious effects of SCBs.

Emergency Department Treatment of Cannabinoid Hyperemesis Syndrome: A Review

BACKGROUND

Cannabinoid hyperemesis syndrome (CHS) is a syndrome of cyclic vomiting associated with chronic cannabis use. As cannabis consumption steadily increases each year, CHS is becoming a commonplace and costly occurrence in hospitals nationwide. Currently, there are no best treatment strategies agreed upon universally.

AREAS OF UNCERTAINTY

Thus far, most data about CHS have come from case reports and case series. Consequently, the pathophysiology of the syndrome is unclear, and its occurrence in some cannabis users, but not others, is not understood.

DATA SOURCES

A literature search was conducted through PubMed, Embase, and Google Scholar from inception until 2017. Publications only in English describing the epidemiology, pathophysiology, diagnostic criteria, and treatments of CHS were incorporated after thorough evaluation. National government surveys were also referred to for current information about the CHS patient population.

RESULTS

CHS should be considered in the differential diagnosis of any patient presenting with persistent nausea and vomiting. In particular, the diagnosis is suggested if the patient demonstrates regular and chronic cannabis use, intractable nausea and vomiting, cyclical vomiting, relief of symptoms with hot baths, and resolution of symptoms after cannabis cessation. There are currently many possible explanations regarding the mechanisms behind CHS. A variety of treatment options have also been examined, including hot water baths, haloperidol, capsaicin, and benzodiazepines.

CONCLUSIONS

CHS is becoming an increasingly prevalent and complicated problem for health care providers and patients. Further research must be done to address the diagnostic and therapeutic challenges of this syndrome.

Is haloperidol the wonder drug for cannabinoid hyperemesis syndrome?

Cannabinoid hyperemesis syndrome (CHS) is a rare clinical syndrome characterised by nausea, cyclic vomiting and severe abdominal pain in association with chronic cannabis use. It is often under-recognised or misdiagnosed, resulting in the unnecessary workup and frequent hospitalisations. Long-term treatment of CHS is abstinence from cannabis, but acute symptomatic management has been a struggle for many clinicians. The present report highlights the use of haloperidol as an agent that successfully and safely treats the unrelenting symptoms of CHS.

Tripping with Synthetic Cannabinoids ("Spice"): Anecdotal and Experimental Observations in Animals and Man

The phenomenon of consuming synthetic cannabinoids ("Spice") for recreational purposes is a fairly recent trend. However, consumption of cannabis dates back millennia, with numerous accounts written on the experience of its consumption, and thousands of scientific reports published on the effects of its constituents in laboratory animals and humans. Here, we focus on consolidating the scientific literature on the effects of "Spice" compounds in various behavioral assays, including assessing abuse liability, tolerance, dependence, withdrawal, and potential toxicity. In most cases, the behavioral effects of "Spice" compounds are compared with those of Δ9-tetrahydrocannabinol. Methodological aspects, such as modes of administration and other logistical issues, are also discussed. As the original "Spice" molecules never were intended for human consumption, scientifically based information about potential toxicity and short- and long-term behavioral effects are very limited. Consequently, preclinical behavioral studies with "Spice" compounds are still in a nascent stage. Research is needed to address the addiction potential and other effects, including propensity for producing tissue/organ toxicity, of these synthetic cannabimimetic "Spice" compounds.

Cannabinoid Hyperemesis Syndrome: An Emerging Drug-Induced Disease

Cannabinoid hyperemesis is a relatively rare but significant adverse effect of chronic marijuana use characterized by severe, cyclic nausea, vomiting, and abdominal pain and marked by compulsive hot-water bathing for temporary symptom relief. A 37-year-old African American male with no significant medical history other than the habitual abuse of marijuana was admitted for intractable nausea, vomiting, and abdominal pain. With the exception of abdominal skin hyperpigmentation and scarring secondary to the direct application of heat through a heating pad, physical examination of the abdomen was unremarkable. Laboratory studies revealed a mild leukocytosis and acute renal dysfunction. All diagnostic examinations were found to be unremarkable or noncontributory to the patient's presenting state. Consistent with previous admissions, the patient's urine toxicology screening was found to be positive for marijuana. After several days of aggressive IV fluid hydration and as needed antiemetics and pain management, all laboratory studies and vital signs returned to baseline and the patient was subsequently discharged. Symptoms of cannabinoid hyperemesis resolve with cannabis cessation and recur when cannabis use is reinitiated, supporting an association between chronic use and cyclic vomiting. A Naranjo algorithm score of 5 revealed a probable incidence of cyclic vomiting associated with chronic cannabis abuse in our patient. Marijuana use, both legal and illegal, is becoming more prevalent in the United States. Given the nationwide increase in marijuana use for recreational and medical reasons, pharmacists and other health care providers should be aware of this interesting drug-induced phenomenon.

Tolerance to the Diuretic Effects of Cannabinoids and Cross-Tolerance to a κ-Opioid Agonist in THC-Treated Mice

Daily treatment with cannabinoids results in tolerance to many, but not all, of their behavioral and physiologic effects. The present studies investigated the effects of 7-day exposure to 10 mg/kg daily of Δ(9)-tetrahydrocannabinol (THC) on the diuretic and antinociceptive effects of THC and the synthetic cannabinoid AM4054. Comparison studies determined diuretic responses to the κ-opioid agonist U50,488 and furosemide. After determination of control dose-response functions, mice received 10 mg/kg daily of THC for 7 days, and dose-response functions were re-determined 24 hours, 7 days, or 14 days later. THC and AM4054 had biphasic diuretic effects under control conditions with maximum effects of 30 and 35 ml/kg of urine, respectively. In contrast, antinociceptive effects of both drugs increased monotonically with dose to >90% of maximal possible effect. Treatment with THC produced 9- and 7-fold rightward shifts of the diuresis and antinociception dose-response curves for THC and, respectively, 7- and 3-fold rightward shifts in the AM4054 dose-response functions. U50,488 and furosemide increased urine output to >35 ml/kg under control conditions. The effects of U50,488 were attenuated after 7-day treatment with THC, whereas the effects of furosemide were unaltered. Diuretic effects of THC and AM4054 recovered to near-baseline levels within 14 days after stopping daily THC injections, whereas tolerance to the antinociceptive effects persisted longer than 14 days. The tolerance induced by 7-day treatment with THC was accompanied by a 55% decrease in the Bmax value for cannabinoid receptors (CB1). These data indicate that repeated exposure to THC produces similar rightward shifts in the ascending and descending limbs of cannabinoid diuresis dose-effect curves and to antinociceptive effects while resulting in a flattening of the U50,488 diuresis dose-effect function.

A high efficacy cannabinergic ligand (AM4054) used as a discriminative stimulus: Generalization to other adamantyl analogs and Δ(9)-THC in rats

In addition to endogenous lipids, the two main cloned receptors (CB1R and CB2R) of the endocannabinoid signaling system (ECS) can be activated (and blocked) by various exogenous ligands. A relatively novel template for CB1R activators contains an adamantyl moiety as a key structural subunit, the first being the cannabinergic AM411. Additional chemical optimization efforts using the classical tricyclic scaffold led to AM4054. Here we explored the in vivo consequences of novel adamantyl analogs in rats trained to recognize the effects of the potent adamantyl cannabinergic AM4054. Rats were trained to discriminate between AM4054 (0.1mg/kg) and vehicle. Three AM4054 analogs and Δ(9)-THC were tested for generalization (substitution) and antagonism was assessed with rimonabant. We found that all cannabinergics resulted in response generalization to the target stimulus AM4054. The order of potency was: AM4054≥AM4083≥AM4050>AM4089>Δ(9)-THC. The CB1R antagonist/inverse agonist rimonabant blocked the discriminative stimulus effects of AM4054. Thus the examined structural modifications affected binding affinities but did not markedly change potencies with the exception of AM4089. In vitro (cAMP assay) functional data have suggested that AM4089 behaves as a partial rather than as a full agonist at CB1R which could explain its lower potency compared to AM4054 (Thakur et al., 2013). The 9β-formyl functionality at C-9 position was identified as an important pharmacophore yielding high in vivo potency. Antagonism by rimonabant suggested CB1R mediation.

Comparisons of Δ9-Tetrahydrocannabinol and Anandamide on a Battery of Cognition-Related Behavior in Nonhuman Primates

The primary psychoactive ingredient of marijuana, Δ(9)-tetrahydrocannabinol (Δ(9)-THC), has medicinal value but also produces unwanted deleterious effects on cognitive function, promoting the search for improved cannabinergic therapeutics. The present studies used a battery of touchscreen procedures in squirrel monkeys to compare the effects of different types of cannabinergic drugs on several measures of performance including learning (repeated acquisition), cognitive flexibility (discrimination reversal), short-term memory (delayed matching-to-sample), attention (psychomotor vigilance), and motivation (progressive ratio). Drugs studied included the cannabinoid agonist Δ(9)-THC, fatty acid amide hydrolase (FAAH) inhibitor cyclohexylcarbamic acid 3-carbamoylbiphenyl-3-yl ester (URB597), and endocannabinoid anandamide and its stable synthetic analog methanandamide [(R)-(+)-arachidonyl-1'-hydroxy-2'-propylamide]. The effects of Δ(9)-THC and anandamide after treatment with the cannabinoid receptor type 1 inverse agonist/antagonist rimonabant [5-(4-chlorophenyl)-1-(2,4-dichloro-phenyl)-4-methyl-N-(piperidin-1-yl)-1Hpyrazole-3-carboxamide] and the FAAH inhibitor URB597, respectively, also were examined. The results showed the following: 1) Δ(9)-THC produced dose-related impairments of discrimination-based cognitive behavior with potency that varied across tasks (discriminative capability < learning < flexibility < short-term memory); 2) anandamide alone and URB597 alone were without effect on all endpoints; 3) anandamide following URB597 pretreatment and methanandamide had negligible effects on discriminative capability, learning, and reversal, but following large doses affected delayed matching-to-sample performance in some subjects; 4) all drugs, except anandamide and URB597, disrupted attention; and 5) progressive ratio breakpoints were generally unaffected by all drugs tested, suggesting little to no effect on motivation. Taken together, these data indicate that metabolically stable forms of anandamide may have lesser adverse effects on cognitive functions than Δ(9)-THC, possibly offering a therapeutic advantage in clinical settings.

Effects of Acute and Repeated Administration of Oxycodone and Naloxone-Precipitated Withdrawal on Intracranial Self-Stimulation in Rats

Incidence of prescription opioid abuse and overdose, often led by oxycodone, continues to increase, producing twice as many overdose deaths as heroin. Surprisingly, preclinical reports relevant to oxycodone's abuse-related effects are relatively sparse considering its history and patient usage. The goal of this study was to characterize dose- and time-dependent effects of acute and repeated oxycodone administration in a frequency-rate intracranial self-stimulation (ICSS) procedure, an assay often predictive of drug-related reinforcing effects, in male Sprague-Dawley rats. We hypothesized that oxycodone would produce a biphasic profile of rate-increasing and rate-decreasing effects maintained by ICSS similar to μ-opioid receptor agonists. Oxycodone (0.03, 0.3, 1, and 3 mg/kg, s.c.) produced dose- and time-dependent alterations on ICSS, with the predicted biphasic profile of rate-increasing effects at lower stimulation frequencies followed by rate-decreasing effects at higher frequencies. Peak effects were observed between 30 and 60 minutes, which were reversed by naloxone pretreatment (30 minutes). Tolerance to rate-decreasing effects was observed over a 5-day period when rats were treated with 1 mg/kg oxycodone twice a day. Subsequently, the dosing regimen was increased to 3 mg/kg twice a day over 10 days, although further marked tolerance did not develop. When then challenged with 10 mg/kg naloxone, a significant suppression below baseline levels of ICSS-maintained responding occurred indicative of dependence that recovered to baseline within 5 hours. The results of this study provide the first report of acute and chronic effects of oxycodone on responding maintained by ICSS presentation and the use of ICSS-maintained responding to characterize its tolerance and dependence effects.

Endogenous opiates and behavior: 2013

This paper is the thirty-sixth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2013 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, and the roles of these opioid peptides and receptors in pain and analgesia; stress and social status; tolerance and dependence; learning and memory; eating and drinking; alcohol and drugs of abuse; sexual activity and hormones, pregnancy, development and endocrinology; mental illness and mood; seizures and neurologic disorders; electrical-related activity and neurophysiology; general activity and locomotion; gastrointestinal, renal and hepatic functions; cardiovascular responses; respiration and thermoregulation; and immunological responses.

Synthetic cannabinoids: epidemiology, pharmacodynamics, and clinical implications

BACKGROUND

Synthetic cannabinoids (SC) are a heterogeneous group of compounds developed to probe the endogenous cannabinoid system or as potential therapeutics. Clandestine laboratories subsequently utilized published data to develop SC variations marketed as abusable designer drugs. In the early 2000s, SC became popular as "legal highs" under brand names such as Spice and K2, in part due to their ability to escape detection by standard cannabinoid screening tests. The majority of SC detected in herbal products have greater binding affinity to the cannabinoid CB1 receptor than does Δ(9)-tetrahydrocannabinol (THC), the primary psychoactive compound in the cannabis plant, and greater affinity at the CB1 than the CB2 receptor. In vitro and animal in vivo studies show SC pharmacological effects 2-100 times more potent than THC, including analgesic, anti-seizure, weight-loss, anti-inflammatory, and anti-cancer growth effects. SC produce physiological and psychoactive effects similar to THC, but with greater intensity, resulting in medical and psychiatric emergencies. Human adverse effects include nausea and vomiting, shortness of breath or depressed breathing, hypertension, tachycardia, chest pain, muscle twitches, acute renal failure, anxiety, agitation, psychosis, suicidal ideation, and cognitive impairment. Long-term or residual effects are unknown. Due to these public health consequences, many SC are classified as controlled substances. However, frequent structural modification by clandestine laboratories results in a stream of novel SC that may not be legally controlled or detectable by routine laboratory tests.

METHODS

We present here a comprehensive review, based on a systematic electronic literature search, of SC epidemiology and pharmacology and their clinical implications.

In utero cannabinoid exposure alters breathing and the response to hypoxia in newborn mice

Cannabis is one of the most commonly used recreational drugs at ages highly correlated with potential pregnancy. Endocannabinoid signalling regulates important stages of neuronal development. When cannabinoid receptors, which are widely distributed through the nervous system, are activated by exogenous cannabinoids, breathing in adult rats is depressed. Here, we show that, in newborn mice, endocannabinoids, through the activation of cannabinoid receptor type 1 (CB1 R), participate in the modulation of respiration and its control. Blocking CB1 Rs at birth suppressed the brake exerted by endocannabinoids on ventilation in basal and in hypoxic conditions. The number of apnoeas and their duration were also minimized by activation of CB1 Rs in normoxic and in hypoxic conditions. However, prenatal cannabis intoxication, caused by a daily injection of WIN55,212-2, in pregnant mice durably modified respiration of the offspring, as shown by hyperventilation in basal conditions, an altered chemoreflex in response to hypoxia, and longer apnoeas. When CB1 Rs were blocked in WIN55,212-2 treated newborns, persistent hyperventilation was still observed, which could partly be explained by a perturbation of the central respiratory network. In fact, in vitro medullary preparations from WIN55,212-2 treated pups, free of peripheral or of supramedullary structures, showed an altered fictive breathing frequency. In conclusion, the endocannabinoid pathway at birth seems to modulate breathing and protect the newborn against apnoeas. However, when exposed prenatally to an excess of cannabinoid, the breathing neuronal network in development seems to be modified, probably rendering the newborn more vulnerable in the face of an unstable environment.

Effects of a novel CB1 agonist on visual attention in male rats: role of strategy and expectancy in task accuracy

The effects of cannabinoid CB1 agonists (including Δ9-tetrahydrocannabinol, the main psychoactive component of marijuana) on attention are uncertain, with reports of impairments, no effects, and occasionally performance enhancements. To better understand these effects, we sought to uncover a role of changing online (within-session) strategy as a possible mediator of the effects of the novel, potent CB1 agonist AM 4054, on a model of sustained attention in male Sprague-Dawley rats. In this operant, two-choice reaction time (RT) task, AM 4054 decreased accuracy in an asymmetric manner; that is, performance was spared on one lever but impaired on the other. Furthermore, this pattern was enhanced by the outcome of the previous trial such that AM 4054 strengthened a win-stay strategy on the "preferred" lever and a lose-shift strategy on the "nonpreferred" lever. This pattern is often found in tests of expectancy; therefore, in a second experiment AM 4054 enhanced expectancy that we engendered by altering the probability of the two stimulus cues. Accuracy was impaired in reporting the less frequent cue, but only after two or more presentations of the more frequent cue. Taking the results of the experiments together, AM 4054 engendered expectancy by increasing the role of previous trial location and outcome on performance of future trials, diminishing stimulus control (and therefore, accuracy). This novel effect of CB1 receptor agonism may contribute to the deleterious effects of cannabinoids on attention.

Behavioral effects of the novel potent cannabinoid CB1 agonist AM 4054

Due to the ubiquity of the CB1 cannabinoid receptor throughout the nervous system, as well as the many potential therapeutic uses of CB1 agonist-based interventions, it is desirable to synthesize novel probes of the CB1 receptor. Here, the acute behavioral effects of systemic (i.p.) administration of the putative novel CB1 full agonist AM 4054 were tested in rats. In Experiment 1, a dose range (0.15625-1.25 mg/kg) of AM 4054 produced effects consistent with CB1 agonism in the cannabinoid tetrad of tasks in rats, including induction of analgesia, catalepsy, hypothermia, and locomotor suppression. These effects were reversed with the CB1-selective inverse agonist AM 251 in Experiment 2, indicating that AM 4054 produced CB1 receptor-mediated effects. Analysis of open-field activity indicated that the reduction in locomotion is more consistent with general motor slowing than anxiogenesis. AM 4054 (0.0625-0.5 mg/kg) also dose-dependently reduced fixed-ratio 5 (FR5) operant responding for food in Experiment 3, and microanalysis of the timing and rate of lever pressing indicated a pattern of suppression similar to other CB1 agonists. Minimum doses of AM 4054 (0.125-0.3125 mg/kg) required to produce significant effects in these behavioral assays were lower than those of many CB1 agonists. It is likely that AM 4054 is a potent pharmacological tool for assessment of cannabinoid receptor function.

Cannabinoid discrimination and antagonism by CB(1) neutral and inverse agonist antagonists

Cannabinoid receptor 1 (CB(1)) inverse agonists (e.g., rimonabant) have been reported to produce adverse effects including nausea, emesis, and anhedonia that limit their clinical applications. Recent laboratory studies suggest that the effects of CB(1) neutral antagonists differ from those of such inverse agonists, raising the possibility of improved clinical utility. However, little is known regarding the antagonist properties of neutral antagonists. In the present studies, the CB(1) inverse agonist SR141716A (rimonabant) and the CB(1) neutral antagonist AM4113 were compared for their ability to modify CB(1) receptor-mediated discriminative stimulus effects in nonhuman primates trained to discriminate the novel CB(1) full agonist AM4054. Results indicate that AM4054 serves as an effective CB(1) discriminative stimulus, with an onset and time course of action comparable with that of the CB(1) agonist Δ(9)-tetrahydrocannabinol, and that the inverse agonist rimonabant and the neutral antagonist AM4113 produce dose-related rightward shifts in the AM4054 dose-effect curve, indicating that both drugs surmountably antagonize the discriminative stimulus effects of AM4054. Schild analyses further show that rimonabant and AM4113 produce highly similar antagonist effects, as evident in comparable pA(2) values (6.9). Taken together with previous studies, the present data suggest that the improved safety profile suggested for CB(1) neutral antagonists over inverse agonists is not accompanied by a loss of antagonist action at CB(1) receptors.