Cannabinoid‐Induced Tetrad in Mice

Evaluation of cannabimimetic effects of selected minor cannabinoids and Terpenoids in mice

BACKGROUND

The cannabis plant contains several cannabinoids, and many terpenoids that give cannabis its distinctive flavoring and aroma. Δ9-Tetrahydrocannabinol (Δ9-THC) is the plant's primary psychoactive constituent. Given the abuse liability of Δ9-THC, assessment of the psychoactive effects of minor cannabinoids and other plant constituents is important, especially for compounds that may be used medicinally. This study sought to evaluate select minor cannabinoids and terpenes for Δ9-THC-like psychoactivity in mouse Δ9-THC drug discrimination and determine their binding affinities at CB1 and CB2 receptors.

METHODS

Δ9-THC, cannabidiol (CBD), cannabinol (CBN), cannabichromene (CBC), cannabichromenevarin (CBCV), Δ8-tetrahydrocannabinol (Δ8-THC), (6aR,9R)-Δ10-tetrahydrocannabinol [(6aR,9R)-Δ10-THC], Δ9-tetrahydrocannabinol varin (THCV), β-caryophyllene (BC), and β-caryophyllene oxide (BCO) were examined.

RESULTS

All minor cannabinoids showed measurable cannabinoid 1 (CB1) and cannabinoid 2 (CB2) receptor binding, with CBC, CBCV, and CBD, showing the weakest CB1 receptor binding affinity. BC and BCO exhibited negligible affinity for both CB1 and CB2 receptors. In drug discrimination, only Δ8-THC fully substituted for Δ9-THC, while CBN and (6aR,9R)-Δ10-THC partially substituted for Δ9-THC. THCV and BCO did not alter the discriminative stimulus effects of Δ9-THC.

CONCLUSION

In summary, only some of myriad cannabinoids and other chemicals found in the cannabis plant bind potently to the identified cannabinoid receptors. Further, only four of the compounds tested herein [Δ9-THC, Δ8-THC, (6aR,9R)-Δ10-THC, and CBN] produced Δ9-THC-like discriminative stimulus effects, suggesting they may possess cannabimimetic subjective effects. Given that the medicinal properties of phytocannabinoids and terpenoids are being investigated scientifically, delineation of their potential adverse effects, including their ability to produce Δ9-THC-like intoxication, is crucial.

Cannabinoid treatments in epilepsy and seizure disorders

Cannabis has been used to treat convulsions and other disorders since ancient times. In the last few decades, preclinical animal studies and clinical investigations have established the role of cannabidiol (CBD) in treating epilepsy and seizures and support potential therapeutic benefits for cannabinoids in other neurological and psychiatric disorders. Here, we comprehensively review the role of cannabinoids in epilepsy. We briefly review the diverse physiological processes mediating the central nervous system response to cannabinoids, including Δ9-tetrahydrocannabinol (Δ9-THC), cannabidiol, and terpenes. Next, we characterize the anti- and proconvulsive effects of cannabinoids from animal studies of acute seizures and chronic epileptogenesis. We then review the clinical literature on using cannabinoids to treat epilepsy, including anecdotal evidence and case studies as well as the more recent randomized controlled clinical trials that led to US Food and Drug Administration approval of CBD for some types of epilepsy. Overall, we seek to evaluate our current understanding of cannabinoids in epilepsy and focus future research on unanswered questions.

CB 1 Cannabinoid Receptor Agonists Induce Acute Respiratory Depression in Awake Mice

Recreational use of synthetic cannabinoid agonists (i.e., "Spice" compounds) that target the Cannabinoid Type 1 receptor (CB 1 ) can cause respiratory depression in humans. However, Δ 9 -tetrahydrocannabinol (THC), the major psychoactive phytocannabinoid in cannabis, is not traditionally thought to interact with CNS control of respiration, based largely upon sparse labeling of CB1 receptors in the medulla and few reports of clinically significant respiratory depression following cannabis overdose. The respiratory effects of CB 1 agonists have rarely been studied in vivo , suggesting that additional inquiry is required to reconcile the conflict between conventional wisdom and human data. Here we used whole body plethysmography to examine the respiratory effects of the synthetic high efficacy CB 1 agonist CP55,940, and the low efficacy CB 1 agonist Δ 9 -tetrahydrocannabinol in male and female mice. CP55,940 and THC, administered systemically, both robustly suppressed minute ventilation. Both cannabinoids also produced sizable reductions in tidal volume, decreasing both peak inspiratory and expiratory flow - measures of respiratory effort. Similarly, both drugs reduced respiratory frequency, decreasing both inspiratory and expiratory time while markedly increasing expiratory pause, and to a lesser extent, inspiratory pause. Respiratory suppressive effects occurred at lower doses in females than in males, and at many of the same doses shown to produce cardinal behavioral signs of CB 1 activation. We next used RNAscope in situ hybridization to localize CB 1 mRNA to glutamatergic neurons in the medullary pre-Bötzinger Complex, a critical nucleus in controlling respiration. Our results show that, contrary to previous conventional wisdom, CB 1 mRNA is expressed in glutamatergic neurons in a brain region essential for breathing and CB 1 agonists can cause significant respiratory depression.

Cannabidiol, but Not Δ9-Tetrahydrocannabinol, Has Strain- and Genotype-Specific Effects in Models of Psychosis

Introduction: Cannabis use has been associated with an increased incidence of psychiatric disorders, yet the underlying neurobiological processes mediating these associations are poorly understood. Whereas exposure to Δ9-tetrahydrocannabinol (THC) has been associated with the development or exacerbation of psychosis, treatment with cannabidiol (CBD) has been associated with amelioration of psychosis. In this study, we demonstrate a complex effect of CBD in mouse models of psychosis, based on factors, including dose, strain, and genotype. Methods: Adult GluN1 knockdown (GluN1KD) and dopamine transporter knockout (DATKO) mice (almost equally balanced for male/female) were acutely treated with vehicle, THC (4 mg/kg), CBD (60, 120 mg/kg), or THC:CBD (1:15, 4:60 mg/kg) and tested in behavioral assays. Results: GluN1KD and DATKO mice displayed hyperactivity, impaired habituation, and sensorimotor gating, along with increased stereotypy and vertical activity. THC, alone and in combination with CBD, produced a robust "dampening" effect on the exploratory behavior regardless of strain or genotype. CBD exhibited a more complex profile. At 60 mg/kg, CBD had minimal effects on horizontal activity, but the effects varied in terms of directionality (increase vs. decrease) in other parameters; effects on stereotypic behaviors differ by genotype, while effects on vertical exploration differ by strain×genotype. CBD at 120 mg/kg had a "dampening" effect on exploration overall, except in GluN1KD mice, where no effect was observed. In terms of sensorimotor gating, both THC and CBD had minimal effects, except for 120 mg/kg CBD, which exacerbated the acoustic startle response. Conclusions: Here, we present a study that highlights the complex mechanism of phytocannabinoids, particularly CBD, in models of psychosis-like behavior. These data require careful interpretation, as agonism of the cannabinoid receptor 1 (CB1) resulting in a decrease in locomotion can be misinterpreted as "antipsychotic-like" activity in murine behavioral outputs of psychosis. Importantly, the THC-mediated decrease in hyperexploratory behavior observed in our models (alone or in combination) was not specific to the genetic mutants, but rather was observed regardless of strain or genotype. Furthermore, CBD treatment, when comparing mutants with their wild-type littermate controls, showed little to no "antipsychotic-like" activity in our models. Therefore, it is not only important to consider dose when designing/interpreting therapeutically driven phytocannabinoid studies, but also effects of strain or genetic vulnerability respective to the general population.

A preclinical model of THC edibles that produces high-dose cannabimimetic responses

No preclinical experimental approach enables the study of voluntary oral consumption of high-concentration Δ9-tetrahydrocannabinol (THC) and its intoxicating effects, mainly owing to the aversive response of rodents to THC that limits intake. Here, we developed a palatable THC formulation and an optimized access paradigm in mice to drive voluntary consumption. THC was formulated in chocolate gelatin (THC-E-gel). Adult male and female mice were allowed ad libitum access for 1 and 2 hr. Cannabimimetic responses (hypolocomotion, analgesia, and hypothermia) were measured following access. Levels of THC and its metabolites were measured in blood and brain tissue. Acute acoustic startle responses were measured to investigate THC-induced psychotomimetic behavior. When allowed access for 2 hr to THC-E-gel on the second day of a 3-day exposure paradigm, adult mice consumed up to ≈30 mg/kg over 2 hr, which resulted in robust cannabimimetic behavioral responses (hypolocomotion, analgesia, and hypothermia). Consumption of the same gelatin decreased on the following third day of exposure. Pharmacokinetic analysis shows that THC-E-gel consumption led to parallel accumulation of THC and its psychoactive metabolite, 11-OH-THC, in the brain, a profile that contrasts with the known rapid decline in brain 11-OH-THC levels following THC intraperitoneal (i.p.) injections. THC-E-gel consumption increased the acoustic startle response in males but not in females, demonstrating a sex-dependent effect of consumption. Thus, while voluntary consumption of THC-E-gel triggered equivalent cannabimimetic responses in male and female mice, it potentiated acoustic startle responses preferentially in males. We built a dose-prediction model that included cannabimimetic behavioral responses elicited by i.p. versus THC-E-gel to test the accuracy and generalizability of this experimental approach and found that it closely predicted the measured acoustic startle results in males and females. In summary, THC-E-gel offers a robust preclinical experimental approach to study cannabimimetic responses triggered by voluntary consumption in mice, including sex-dependent psychotomimetic responses.

Effects of acute Δ9-tetrahydrocannabinol on behavior and the endocannabinoid system in HIV-1 Tat transgenic female and male mice

Cannabis use is highly prevalent especially among people living with HIV (PLWH). Activation of the anti-inflammatory and neuroprotective endocannabinoid system by phytocannabinoids, i.e. Δ9-tetrahydrocannabinol (THC), has been proposed to reduce HIV symptoms. However, THC's effects on HIV-related memory deficits are unclear. Using HIV-1 Tat transgenic mice, the current study investigates acute THC effects on various behavioral outcomes and the endocannabinoid system. For the rodent tetrad model, THC doses (1, 3, 10 mg/kg) induced known antinociceptive effects, with Tat induction increasing antinociceptive THC effects at 3 and 10 mg/kg doses. Only minor or no effects were noted for acute THC on body temperature, locomotor activity, and coordination. Increased anxiety-like behavior was found for females compared to males, but acute THC had no effect on anxiety. Object recognition memory was diminished by acute THC in Tat(-) females but not Tat(+) females, without affecting males. The endocannabinoid system and related lipids were not affected by acute THC, except for THC-induced decreases in CB1R protein expression levels in the spinal cord of Tat(-) mice. Female sex and Tat induction was associated with elevated 2-AG, AEA, AA, CB1R, CB2R, FAAH and/or MAGL expression in various brain regions. Further, AEA levels in the prefrontal cortex of Tat(+) females were negatively associated with object recognition memory. Overall, findings indicate that acute THC exerts differential effects on antinociception and memory, dependent on sex and HIV Tat expression, potentially in relation to an altered endocannabinoid system, which may be of relevance in view of potential cannabis-based treatment options for PLWH.

Sex Differences in Plasma, Adipose Tissue, and Central Accumulation of Cannabinoids, and Behavioral Effects of Oral Cannabis Consumption in Male and Female C57BL/6 Mice

BACKGROUND

Cannabis edibles are an increasingly popular form of cannabis consumption. Oral consumption of cannabis has distinct physiological and behavioral effects compared with injection or inhalation. An animal model is needed to understand the pharmacokinetics and physiological effects of oral cannabis consumption in rodents as a model for human cannabis edible use.

METHODS

Adult male and female C57BL/6 mice received a single dose of commercially available cannabis oil (5 mg/kg Δ⁹-tetrahydrocannabinol [THC]) by oral gavage. At 0.5, 1, 2, 3, and 6 hours post exposure, plasma, hippocampus, and adipose tissue were collected for THC, 11-OH-THC, and THC-COOH measures.

RESULTS

We report delayed time to peak THC and 11-OH-THC concentrations in plasma, brain, and adipose tissue, which is consistent with human pharmacokinetics studies. We also found sex differences in the cannabis tetrad: (1) female mice had a delayed hypothermic effect 6 hours post consumption, which was not present in males; (2) females had stronger catalepsy than males; (3) males were less mobile following cannabis exposure, whereas female mice showed no difference in locomotion but an anxiogenic effect at 3 hours post exposure; and (4) male mice displayed a longer-lasting antinociceptive effect of oral cannabis.

CONCLUSIONS

Oral cannabis consumption is a translationally relevant form of administration that produces similar physiological effects as injection or vaping administration and thus should be considered as a viable approach for examining the physiological effects of cannabis moving forward. Furthermore, given the strong sex differences in metabolism of oral cannabis, these factors should be carefully considered when designing animal studies on the effects of cannabis.

Striatopallidal cannabinoid type-1 receptors mediate amphetamine-induced sensitization

Repeated exposure to psychostimulants, such as amphetamine, causes a long-lasting enhancement in the behavioral responses to the drug, called behavioral sensitization.1 This phenomenon involves several neuronal systems and brain areas, among which the dorsal striatum plays a key role.2 The endocannabinoid system (ECS) has been proposed to participate in this effect, but the neuronal basis of this interaction has not been investigated.3 In the CNS, the ECS exerts its functions mainly acting through the cannabinoid type-1 (CB1) receptor, which is highly expressed at terminals of striatal medium spiny neurons (MSNs) belonging to both the direct and indirect pathways.4 In this study, we show that, although striatal CB1 receptors are not involved in the acute response to amphetamine, the behavioral sensitization and related synaptic changes require the activation of CB1 receptors specifically located at striatopallidal MSNs (indirect pathway). These results highlight a new mechanism of psychostimulant sensitization, a phenomenon that plays a key role in the health-threatening effects of these drugs.

Impact of early-life lead exposure on adult delta-9-tetrahydrocannabinol sensitivity in male and female C57BL6/J mice

Environmental exposure to lead (Pb) and cannabis use are two of the largest public health issues facing modern society in the United States and around the world. Exposure to Pb in early life has been unequivocally shown to have negative impacts on development, and recent research is mounting showing that it may also predispose individuals for risk of developing substance use disorders (SUD). At the same time, societal and legal attitudes towards cannabis (the main psychoactive component of which is delta-9-tetrahydrocannabinol) have been shifting, and many American states have legalized the recreational use of cannabis. It is also the 3rd most widely used drug of abuse in the US, and rates of cannabis use disorder are on the rise. Here we establish a link between early life Pb exposure and later THC-related behavior in C57BL6/J mice, as has been demonstrated for other drugs of abuse. The study seeks to answer whether Pb exposure affects physiological/behavioral THC sensitivity (as measured by the cannabinoid-induced tetrad). It was hypothesized that Pb exposure would decrease THC sensitivity and that sex-dependent effects of Pb-exposure and THC would be observed. Interestingly, results showed that THC sensitivity was increased by Pb exposure, but only in female mice. Future research will fully explore the implications of these findings, namely how these effects impact THC self-administration and the mechanism(s) by which developmental Pb exposure produces these effects.

Synthesis and pharmacological activity of the epimers of hexahydrocannabinol (HHC)

Cannabis is a multifaceted plant with numerous therapeutic properties on one hand, and controversial psychotropic activities on the other hand, which are modulated by CB1 endocannabinoid receptors. Δ9-Tetrahydrocannabinol (Δ9-THC) has been identified as the main component responsible for the psychotropic effects, while its constitutional isomer cannabidiol (CBD) has shown completely different pharmacological properties. Due to its reported beneficial effects, Cannabis has gained global popularity and is openly sold in shops and online. To circumvent legal restrictions, semi-synthetic derivatives of CBD are now frequently added to cannabis products, producing "high" effects similar to those induced by Δ9-THC. The first semi-synthetic cannabinoid to appear in the EU was obtained through cyclization and hydrogenation of CBD, and is known as hexahydrocannabinol (HHC). Currently, there is limited knowledge regarding HHC, its pharmacological properties, and its prevalence, as it is not commonly investigated in routine toxicological assays. In this study, synthetic strategies were explored to obtain an excess of the active epimer of HHC. Furthermore, the two epimers were purified and individually tested for their cannabinomimetic activity. Lastly, a simple and rapid chromatographic method employing a UV detector and a high-resolution mass spectrometer was applied to identify and quantify up to ten major phytocannabinoids, as well as the HHC epimers, in commercial cannabis samples.

Role of Neuronal Nicotinic Acetylcholine Receptors in Cannabinoid Dependence

Cannabis is among the most widely consumed psychoactive drugs around the world and cannabis use disorder (CUD) has no current approved pharmacological treatment. Nicotine and cannabis are commonly co-used which suggests there to be overlapping neurobiological actions supported primarily by the co-distribution of both receptor systems in the brain. There appears to be strong rationale to explore the role that nicotinic receptors play in cannabinoid dependence. Preclinical studies suggest that the ɑ7 nAChR subtype may play a role in modulating the reinforcing and discriminative stimulus effects of cannabinoids, while the ɑ4β2 * nAChR subtype may be involved in modulating the motor and sedative effects of cannabinoids. Preclinical and human genetic studies point towards a potential role of the ɑ5, ɑ3, and β4 nAChR subunits in CUD, while human GWAS studies strongly implicate the ɑ2 subunit as playing a role in CUD susceptibility. Clinical studies suggest that current smoking cessation agents, such as varenicline and bupropion, may also be beneficial in treating CUD, although more controlled studies are necessary. Additional behavioral, molecular, and mechanistic studies investigating the role of nAChR in the modulation of the pharmacological effects of cannabinoids are needed.

THC and CBD: Similarities and differences between siblings

Δ9-tetrahydrocannabinol (THC) and its sibling, cannabidiol (CBD), are produced by the same Cannabis plant and have similar chemical structures but differ dramatically in their mechanisms of action and effects on brain functions. Both THC and CBD exhibit promising therapeutic properties; however, impairments and increased incidence of mental health diseases are associated with acute and chronic THC use, respectively, and significant side effects are associated with chronic use of high-dose CBD. This review covers recent molecular and preclinical discoveries concerning the distinct mechanisms of action and bioactivities of THC and CBD and their impact on human behavior and diseases. These discoveries provide a foundation for the development of cannabinoid-based therapeutics for multiple devastating diseases and to assure their safe use in the growing legal market of Cannabis-based products.

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.

Vaporized Delta-9-tetrahydrocannabinol Inhalation in Female Sprague Dawley Rats: A Pharmacokinetic and Behavioral Assessment

BACKGROUND

Delta-9-tetrahydrocannabinol (THC) is the main psychoactive component of cannabis. Historically, rodent studies examining the effects of THC have used intraperitoneal injection as the route of administration, heavily focusing on male subjects. However, human cannabis use is often through inhalation rather than injection.

OBJECTIVE

We sought to characterize the pharmacokinetic and phenotypic profile of acutely inhaled THC in female rats, compared to intraperitoneal injection, to identify any differences in exposure of THC between routes of administration.

METHODS

Adult female rats were administered THC via inhalation or intraperitoneal injection. Serum samples from multiple time points were analyzed for THC and metabolites 11-hydroxy-delta-9-tetrahydrocannabinol and 11-nor-9-carboxy-delta-9-tetrahydrocannabinol using ultra-performance liquid chromatography-tandem mass spectrometry. Rats were similarly treated for locomotor activity analysis.

RESULTS

Rats treated with 2 mg/kg THC intraperitoneally reached a maximum serum THC concentration of 107.7 ± 21.9 ng/mL. Multiple THC inhalation doses were also examined (0.25 mL of 40 or 160 mg/mL THC), achieving maximum concentrations of 43.3 ± 7.2 and 71.6 ± 22.5 ng/mL THC in serum, respectively. Significantly reduced vertical locomotor activity was observed in the lower inhaled dose of THC and the intraperitoneal injected THC dose compared to vehicle treatment.

CONCLUSION

This study established a simple rodent model of inhaled THC, demonstrating the pharmacokinetic and locomotor profile of acute THC inhalation, compared to an i.p. injected THC dose in female subjects. These results will help support future inhalation THC rat research which is especially important when researching behavior and neurochemical effects of inhaled THC as a model of human cannabis use.

Decursinol-mediated antinociception and anti-allodynia in acute and neuropathic pain models in male mice: Tolerance and receptor profiling

Korean scientists have shown that oral administration of Angelica gigas Nakai (AGN) root alcoholic extract and the metabolite of its pyranocoumarins, decursinol, have antinociceptive properties across various thermal and acute inflammatory pain models. The objectives of this study were 1) to assess whether tolerance develops to the antinociceptive effects of once-daily intraperitoneally administered decursinol (50 mg/kg) in acute thermal pain models, 2) to establish its anti-allodynic efficacy and potential tolerance development in a model of chemotherapy-evoked neuropathic pain (CENP) and 3) to probe the involvement of select receptors in mediating the pain-relieving effects with antagonists. The results show that decursinol induced antinociception in both the hot plate and tail-flick assays and reversed mechanical allodynia in mice with cisplatin-evoked neuropathic pain. Tolerance was detected to the antinociceptive effects of decursinol in the hot plate and tail-flick assays and to the anti-allodynic effects of decursinol in neuropathic mice. Pretreatment with either the 5-HT2 antagonist methysergide, the 5-HT2A antagonist volinanserin, or the 5-HT2C antagonist SB-242084 failed to attenuate decursinol-induced antinociception in the tail-flick assay. While pretreatment with the cannabinoid inverse agonists rimonabant and SR144528 failed to modify decursinol-induced anti-allodynia, pretreatment with the opioid antagonist naloxone partially attenuated the anti-allodynic effects of decursinol. In conclusion, our data support decursinol as an active phytochemical of AGN having both antinociceptive and anti-allodynic properties. Future work warrants a more critical investigation of potential receptor mechanisms as they are likely more complicated than initially reported.

TRPV1: A Common Denominator Mediating Antinociceptive and Antiemetic Effects of Cannabinoids

The most common medicinal claims for cannabis are relief from chronic pain, stimulation of appetite, and as an antiemetic. However, the mechanisms by which cannabis reduces pain and prevents nausea and vomiting are not fully understood. Among more than 450 constituents in cannabis, the most abundant cannabinoids are Δ⁹-tetrahydrocannabinol (THC) and cannabidiol (CBD). Cannabinoids either directly or indirectly modulate ion channel function. Transient receptor potential vanilloid 1 (TRPV1) is an ion channel responsible for mediating several modalities of pain, and it is expressed in both the peripheral and the central pain pathways. Activation of TRPV1 in sensory neurons mediates nociception in the ascending pain pathway, while activation of TRPV1 in the central descending pain pathway, which involves the rostral ventral medulla (RVM) and the periaqueductal gray (PAG), mediates antinociception. TRPV1 channels are thought to be implicated in neuropathic/spontaneous pain perception in the setting of impaired descending antinociceptive control. Activation of TRPV1 also can cause the release of calcitonin gene-related peptide (CGRP) and other neuropeptides/neurotransmitters from the peripheral and central nerve terminals, including the vagal nerve terminal innervating the gut that forms central synapses at the nucleus tractus solitarius (NTS). One of the adverse effects of chronic cannabis use is the paradoxical cannabis-induced hyperemesis syndrome (HES), which is becoming more common, perhaps due to the wider availability of cannabis-containing products and the chronic use of products containing higher levels of cannabinoids. Although, the mechanism of HES is unknown, the effective treatment options include hot-water hydrotherapy and the topical application of capsaicin, both activate TRPV1 channels and may involve the vagal-NTS and area postrema (AP) nausea and vomiting pathway. In this review, we will delineate the activation of TRPV1 by cannabinoids and their role in the antinociceptive/nociceptive and antiemetic/emetic effects involving the peripheral, spinal, and supraspinal structures.

Development of Cross-Reactive Antibodies for the Identification and Treatment of Synthetic Cannabinoid Receptor Agonist Toxicity

Synthetic cannabinoid receptor agonists (SCRAs) are compounds that mimic the pharmacology of the psychoactive components in cannabis. These compounds are structurally diverse, inexpensive, commercially available, and difficult to identify with modern analytical methods, making them highly accessible for recreational use. Suspected SCRA toxicity, which can present with a breadth of cardiovascular, gastrointestinal, and neurological disturbances, is currently addressed through symptom management followed by a toxicological screening that often occurs long after patient discharge. Here, we report the development of four cross-reactive anti-SCRA bioconjugate vaccines as a platform for developing improved diagnostic and therapeutic interventions against SCRA intoxication, using SCRA-resembling small molecule haptens that combine common subregional motifs occurring within and across different generations of SCRA molecules. Using a combination of multiplexed competitive ELISA screening and chemoinformatic analyses, it was found that the antibodies resulting from vaccination with these bioconjugates demonstrated their ability to detect multiple SCRAs with a Tanimoto minimum common structure score of 0.6 or greater, at concentrations below 8 ng/mL. The scope of SCRAs detectable using these haptens was found to include both bioisosteric and non-bioisosteric variants within the core and tail subregions, as well as SCRAs bearing valine-like head subregions, which are not addressed by commercially available ELISA screening approaches. Vaccination with these bioconjugates was also found to prevent the changes in locomotion and body temperature that were induced by a panel of SCRAs at doses of 1 and 3 mg/kg. Further refinement of this genericized hapten design and cross-reactivity-prioritizing approach may enable the rapid detection of otherwise cryptic SCRAs that arise during overdose outbreaks, and could ultimately lead to identification of monoclonal antibody species applicable for overdose reversal.

The cannabinoid agonist CB-13 produces peripherally mediated analgesia in mice but elicits tolerance and signs of central nervous system activity with repeated dosing

ABSTRACT

Activation of cannabinoid receptor type 1 (CB 1 ) produces analgesia in a variety of preclinical models of pain; however, engagement of central CB 1 receptors is accompanied by unwanted side effects, such as psychoactivity, tolerance, and dependence. Therefore, some efforts to develop novel analgesics have focused on targeting peripheral CB 1 receptors to circumvent central CB 1 -related side effects. In the present study, we evaluated the effects of acute and repeated dosing with the peripherally selective CB 1 -preferring agonist CB-13 on nociception and central CB 1 -related phenotypes in a model of inflammatory pain in mice. We also evaluated cellular mechanisms underlying CB-13-induced antinociception in vitro using cultured mouse dorsal root ganglion neurons. CB-13 reduced inflammation-induced mechanical allodynia in male and female mice in a peripheral CB 1 -receptor-dependent manner and relieved inflammatory thermal hyperalgesia. In cultured mouse dorsal root ganglion neurons, CB-13 reduced TRPV1 sensitization and neuronal hyperexcitability induced by the inflammatory mediator prostaglandin E 2 , providing potential mechanistic explanations for the analgesic actions of peripheral CB 1 receptor activation. With acute dosing, phenotypes associated with central CB 1 receptor activation occurred only at a dose of CB-13 approximately 10-fold the ED 50 for reducing allodynia. Strikingly, repeated dosing resulted in both analgesic tolerance and CB 1 receptor dependence, even at a dose that did not produce central CB 1 -receptor-mediated phenotypes on acute dosing. This suggests that repeated CB-13 dosing leads to increased CNS exposure and unwanted engagement of central CB 1 receptors. Thus, caution is warranted regarding therapeutic use of CB-13 with the goal of avoiding CNS side effects. Nonetheless, the clear analgesic effect of acute peripheral CB 1 receptor activation suggests that peripherally restricted cannabinoids are a viable target for novel analgesic development.

Review of delta-8-tetrahydrocannabinol (Δ8 -THC): Comparative pharmacology with Δ9 -THC

The use of the intoxicating cannabinoid delta-8-tetrahydrocannabinol (Δ⁸ -THC) has grown rapidly over the last several years. There have been dozens of Δ⁸ -THC studies dating back over many decades, yet no review articles have comprehensively covered these findings. In this review, we summarize the pharmacological studies of Δ⁸ -THC, including receptor binding, cell signalling, in vivo cannabimimetic activity, clinical activity and pharmacokinetics. We give special focus to studies that directly compared Δ⁸ -THC to its more commonly studied isomer, Δ⁹ -THC. Overall, the pharmacokinetics and pharmacodynamics of Δ⁸ -THC and Δ⁹ -THC are very similar. Δ⁸ -THC is a partial agonist of the cannabinoid CB₁ receptor and has cannabimimetic activity in both animals and humans. The reduced potency of Δ⁸ -THC in clinical studies compared with Δ⁹ -THC can be explained by weaker cannabinoid CB₁ receptor affinity, although there are other plausible mechanisms that may contribute. We highlight the gaps in our knowledge of Δ⁸ -THC pharmacology where further studies are needed, particularly in humans.

Mepirapim, a Novel Synthetic Cannabinoid, Induces Addiction-Related Behaviors through Neurochemical Maladaptation in the Brain of Rodents

Mepirapim is a synthetic cannabinoid that has recently been abused for recreational purposes. Although serious side effects have been reported from users, the dangerous pharmacological effects of Mepirapim have not been scientifically demonstrated. In this study, we investigated the addictive potential of Mepirapim through an intravenous self-administration test and a conditioned place preference test in rodents. Moreover, to determine whether the pharmacological effects of Mepirapim are mediated by cannabinoid receptors, we investigated whether Mepirapim treatment induces cannabinoid tetrad symptoms in mice. Lastly, to identify Mepirapim induced neurochemical maladaptation in the brains of mice, we performed microdialysis, western blots and neurotransmitter enzyme-linked immunosorbent assays. In the results, Mepirapim supported the maintenance of intravenous self-administration and the development of conditioned place preference. As a molecular mechanism of Mepirapim addiction, we identified a decrease in GABAeric signalling and an increase in dopaminergic signalling in the brain reward circuit. Finally, by confirming the Mepirapim-induced expression of cannabinoid tetrad symptoms, we confirmed that Mepirapim acts pharmacologically through cannabinoid receptor one. Taken together, we found that Mepirapim induces addiction-related behaviours through neurochemical maladaptation in the brain. On the basis of these findings, we propose the strict regulation of recreational abuse of Mepirapim.

Cannabinoid tetrad effects of oral Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD) in male and female rats: sex, dose-effects and time course evaluations

RATIONALE

The legalization of medicinal use of Cannabis sativa in most US states and the removal of hemp from the Drug Enforcement Agency (DEA) controlled substances act has resulted in a proliferation of products containing Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD) for oral consumption (e.g., edibles, oils, and tinctures) that are being used for recreational and medicinal purposes.

OBJECTIVE

This study examined the effects of cannabinoids THC and CBD when administered orally on measures of pain sensitivity, body temperature, locomotor activity, and catalepsy (i.e., cannabinoid tetrad) in male and female Sprague Dawley rats.

METHODS

Rats (N = 24, 6 per sex/drug group) were administered THC (1-20 mg/kg), CBD (3-30 mg/kg), or sesame oil via oral gavage. Thermal and mechanical pain sensitivity (tail flick assay, von Frey test), rectal measurements for body temperature, locomotor activity, and the bar-test of catalepsy were completed. A separate group of rats (N = 8/4 per sex) was administered morphine (5-20 mg/kg; intraperitoneal, IP) and evaluated for pain sensitivity as a positive control.

RESULTS

We observed classic tetrad effects of antinociception, hypothermia, hyper- and hypolocomotion, and catalepsy after oral administration of THC that were long lasting (> 7 h). CBD modestly increased mechanical pain sensitivity and produced sex-dependent effects on body temperature and locomotor activity.

CONCLUSIONS

Oral THC and CBD produced long lasting effects that differed in magnitude and time course when compared with other routes of administration. Examination of cannabinoid effects administered via different routes of administration, species, and in both males and females is critical to enhance translation.

Translational models of cannabinoid vapor exposure in laboratory animals

Cannabis is one of the most frequently used psychoactive substances in the world. The most common route of administration for cannabis and cannabinoid constituents such as Δ-9-tetrahydrocannabinol (THC) and cannabidiol (CBD) is via smoking or vapor inhalation. Preclinical vapor models have been developed, although the vaporization devices and delivery methods vary widely across laboratories. This review examines the emerging field of preclinical vapor models with a focus on cannabinoid exposure in order to (1) summarize vapor exposure parameters and other methodological details across studies; (2) discuss the pharmacological and behavioral effects produced by exposure to vaporized cannabinoids; and (3) compare behavioral effects of cannabinoid vapor administration with those of other routes of administration. This review will serve as a guide for past and current vapor delivery methods in animals, synergize findings across studies, and propose future directions for this area of research.

Structure-activity relationships for 5F-MDMB-PICA and its 5F-pentylindole analogs to induce cannabinoid-like effects in mice

Synthetic cannabinoid receptor agonists (SCRAs) are an evolving class of new psychoactive substances found on recreational drug markets worldwide. The indole-containing compound, 5F-MDMB-PICA, is a popular SCRA associated with serious medical consequences, including overdose and hospitalizations. In vitro studies reveal that 5F-MDMB-PICA is a potent agonist at cannabinoid type 1 receptors (CB₁), but little information exists regarding in vivo pharmacology of the drug. To this end, we examined the in vitro and in vivo cannabinoid-like effects produced by 5F-MDMB-PICA and related 5F-pentylindole analogs with differing composition of the head group moiety (i.e., 5F-NNEI, 5F-SDB-006, 5F-CUMYL-PICA, 5F-MMB-PICA). In mouse brain membranes, 5F-MDMB-PICA and its analogs inhibited binding to [³H]rimonabant-labeled CB₁ and displayed agonist actions in [³⁵S]GTPγS functional assays. 5F-MDMB-PICA exhibited the highest CB₁ affinity (K_i = 1.24 nM) and functional potency (EC₅₀ = 1.46 nM), but head group composition markedly influenced activity in both assays. For example, the 3,3-dimethylbutanoate (5F-MDMB-PICA) and cumyl (5F-CUMYL-PICA) head groups engendered high CB₁ affinity and potency, whereas a benzyl (5F-SDB-006) head group did not. In C57BL/6J mice, all 5F-pentylindole SCRAs produced dose- and time-dependent hypothermia, catalepsy, and analgesia that were reversed by rimonabant, indicating CB₁ involvement. In vitro K_i and EC₅₀ values were positively correlated with in vivo ED₅₀ potency estimates. Our findings demonstrate that 5F-MDMB-PICA is a potent SCRA, and subtle alterations to head group composition can have profound influence on pharmacological effects at CB₁. Importantly, measures of CB₁ binding and efficacy in mouse brain tissue seem to accurately predict in vivo drug potency in this species.

Structure-activity relationships of valine, tert-leucine, and phenylalanine amino acid-derived synthetic cannabinoid receptor agonists related to ADB-BUTINACA, APP-BUTINACA, and ADB-P7AICA

Synthetic cannabinoid receptor agonists (SCRAs) remain one the most prevalent classes of new psychoactive substances (NPS) worldwide, and examples are generally poorly characterised at the time of first detection. We have synthesised a systematic library of amino acid-derived indole-, indazole-, and 7-azaindole-3-carboxamides related to recently detected drugs ADB-BUTINACA, APP-BUTINACA and ADB-P7AICA, and characterised these ligands for in vitro binding and agonist activity at cannabinoid receptor subtypes 1 and 2 (CB1 and CB2), and in vivo cannabimimetic activity. All compounds showed high affinity for CB1 (K i 0.299-538 nM) and most at CB2 (K i = 0.912-2190 nM), and most functioned as high efficacy agonists of CB1 and CB2 in a fluorescence-based membrane potential assay and a βarr2 recruitment assay (NanoBiT®), with some compounds being partial agonists in the NanoBiT® assay. Key structure-activity relationships (SARs) were identified for CB1/CB2 binding and CB1/CB2 functional activities; (1) for a given core, affinities and potencies for tert-leucinamides (ADB-) > valinamides (AB-) ≫ phenylalaninamides (APP-); (2) for a given amino acid side-chain, affinities and potencies for indazoles > indoles ≫ 7-azaindoles. Radiobiotelemetric evaluation of ADB-BUTINACA, APP-BUTINACA and ADB-P7AICA in mice demonstrated that ADB-BUTINACA and ADB-P7AICA were cannabimimetic at 0.1 mg kg-1 and 10 mg kg-1 doses, respectively, as measured by pronounced decreases in core body temperature. APP-BUTINACA failed to elicit any hypothermic response up to the maximally tested 10 mg kg-1 dose, yielding an in vivo potency ranking of ADB-BUTINACA > ADB-P7AICA > APP-BUTINACA.

Cannabinoids in Breast Cancer: Differential Susceptibility According to Subtype

Although cannabinoids have been used for centuries for diverse pathological conditions, recently, their clinical interest and application have emerged due to their diverse pharmacological properties. Indeed, it is well established that cannabinoids exert important actions on multiple sclerosis, epilepsy and pain relief. Regarding cancer, cannabinoids were first introduced to manage chemotherapy-related side effects, though several studies demonstrated that they could modulate the proliferation and death of different cancer cells, as well as angiogenesis, making them attractive agents for cancer treatment. In relation to breast cancer, it has been suggested that estrogen receptor-negative (ER-) cells are more sensitive to cannabinoids than estrogen receptor-positive (ER+) cells. In fact, most of the studies regarding their effects on breast tumors have been conducted on triple-negative breast cancer (TNBC). Nonetheless, the number of studies on human epidermal growth factor receptor 2-positive (HER2+) and ER+ breast tumors has been rising in recent years. However, besides the optimistic results obtained thus far, there is still a long way to go to fully understand the role of these molecules. This review intends to help clarify the clinical potential of cannabinoids for each breast cancer subtype.

In vivo Evidence for Brain Region-Specific Molecular Interactions Between Cannabinoid and Orexin Receptors

The endocannabinoid and orexin neuromodulatory systems serve key roles in many of the same biological functions such as sleep, appetite, pain processing, and emotional behaviors related to reward. The type 1 cannabinoid receptor (CB1R) and both subtypes of the orexin receptor, orexin receptor type 1 (OX1R) and orexin receptor type 2 (OX2R) are not only expressed in the same brain regions modulating these functions, but physically interact as heterodimers in recombinant and neuronal cell cultures. In the current study, male and female C57BL/6 mice were co-treated with the cannabinoid receptor agonist CP55,940 and either the OX2R antagonist TCS-OX2-29 or the dual orexin receptor antagonist (DORA) TCS-1102. Mice were then evaluated for catalepsy, body temperature, thermal anti-nociception, and locomotion, after which their brains were collected for receptor colocalization analysis. Combined treatment with the DORA TCS-1102 and CP55,940 potentiated catalepsy more than CP55,940 alone, but this effect was not observed for changes in body temperature, nociception, locomotion, or via selective OX2R antagonism. Co-treatment with CP55,940 and TCS-1102 also led to increased CB1R-OX1R colocalization in the ventral striatum. This was not seen following co-treatment with TCS-OX2-29, nor in CB1R-OX2R colocalization. The magnitude of effects following co-treatment with CP55,940 and either the DORA or OX2R-selective antagonist was greater in males than females. These data show that CB1R-OX1R colocalization in the ventral striatum underlies cataleptic additivity between CP55,940 and the DORA TCS-1102. Moreover, cannabinoid-orexin receptor interactions are sex-specific with regards to brain region and functionality. Physical or molecular interactions between these two systems may provide valuable insight into drug-drug interactions between cannabinoid and orexin drugs for the treatment of insomnia, pain, and other disorders.

Receptor mechanisms underlying the CNS effects of cannabinoids: CB1 receptor and beyond

Cannabis legalization continues to progress in many US states and other countries. Δ9-tetrahydrocannabinol (Δ9-THC) is the major psychoactive constituent in cannabis underlying both its abuse potential and the majority of therapeutic applications. However, the neural mechanisms underlying cannabis action are not fully understood. In this chapter, we first review recent progress in cannabinoid receptor research, and then examine the acute CNS effects of Δ9-THC or other cannabinoids (WIN55212-2) with a focus on their receptor mechanisms. In experimental animals, Δ9-THC or WIN55212-2 produces classical pharmacological effects (analgesia, catalepsy, hypothermia, hypolocomotion), biphasic changes in affect (reward vs. aversion, anxiety vs. anxiety relief), and cognitive deficits (spatial learning and memory, short-term memory). Accumulating evidence indicates that activation of CB1Rs underlies the majority of Δ9-THC or WIN55121-2's pharmacological and behavioral effects. Unexpectedly, glutamatergic CB1Rs preferentially underlie cannabis action relative to GABAergic CB1Rs. Functional roles for CB1Rs expressed on astrocytes and mitochondria have also been uncovered. In addition, Δ9-THC or WIN55212-2 is an agonist at CB2R, GPR55 and PPARγ receptors and recent studies implicate these receptors in a number of their CNS effects. Other receptors (such as serotonin, opioid, and adenosine receptors) also modulate Δ9-THC's actions and their contributions are detailed. This chapter describes the neural mechanisms underlying cannabis action, which may lead to new discoveries in cannabis-based medication development for the treatment of cannabis use disorder and other human diseases.

Endocannabinoid System Attenuates Oxaliplatin-Induced Peripheral Sensory Neuropathy Through the Activation of CB1 Receptors

Oxaliplatin-induced neurotoxicity is expressed as a dose-limiting peripheral sensory neuropathy (PSN). Cannabinoid substances have been investigated for the analgesic effect. This study aimed to investigate the role of cannabinoid receptors in oxaliplatin-associated PSN. Swiss male mice received nine oxaliplatin injections (2 mg/kg, i.v.). Mechanical and thermal nociceptive tests were performed for 56 days. CB1, CB2, and c-Fos expression were assessed in dorsal root ganglia (DRG), spinal cord (SC), trigeminal ganglia (TG), spinal trigeminal nucleus caudalis (Sp5C), and periaqueductal gray (PAG). Iba-1 expression was assessed in DRG and ATF3 in TG. Cannabidiol (10 mg/kg, p.o.) or a CB1/CB2 non-selective agonist (WIN 55,212-2; 0.5 mg/kg, s.c.) or AM251 (CB1 antagonist) or AM630 (CB2 antagonist) (3 mg/kg, i.p.) were injected before oxaliplatin. Oxaliplatin increased CB1 in DRG, SC, TG, Sp5C, and ventrolateral PAG, with no interference in CB2 expression. Cannabidiol increased CB1 in DRG, reduced mechanical hyperalgesia and c-Fos expression in DRG and SC. Additionally, WIN 55,212-2 increased CB1 in DRG, reduced mechanical hyperalgesia, cold allodynia and c-Fos expression in DRG and SC. CB1 blockage hastened the cold allodynia response, but the CB2 antagonist failed to modulate the oxaliplatin-induced nociceptive behavior. Oxaliplatin also increased Iba-1 in DRG, suggesting immune response modulation which was reduced by cannabidiol and enhanced by AM630. The modulation of the endocannabinoid system, through the CB1 receptor, attenuates the oxaliplatin-associated PNS. The activation of the endocannabinoid system could be considered as a therapeutic target for controlling oxaliplatin-associated neuropathy.

Behavioral aspects and neurobiological properties underlying medical cannabis treatment in Shank3 mouse model of autism spectrum disorder

Autism spectrum disorder (ASD) is a neurodevelopmental disease with a wide spectrum of manifestation. The core symptoms of ASD are persistent deficits in social communication, and restricted and repetitive patterns of behavior, interests, or activities. These are often accompanied by intellectual disabilities. At present, there is no designated effective treatment for the core symptoms and co-morbidities of ASD. Recently, interest is rising in medical cannabis as a treatment for ASD, with promising clinical data. However, there is a notable absence of basic pre-clinical research in this field. In this study, we investigate the behavioral and biochemical effects of long-term oral treatment with CBD-enriched medical cannabis oil in a human mutation-based Shank3 mouse model of ASD. Our findings show that this treatment alleviates anxiety and decreases repetitive grooming behavior by over 70% in treated mutant mice compared to non-treated mutant mice. Furthermore, we were able to uncover the involvement of CB1 receptor (CB1R) signaling in the Avidekel oil mechanism, alongside a mitigation of cerebrospinal fluid (CSF) glutamate concentrations. Subsequently, RNA sequencing (RNA seq) of cerebellar brain samples revealed changes in mRNA expression of several neurotransmission-related genes post-treatment. Finally, our results question the relevancy of CBD enrichment of medical cannabis for treating the core symptoms of ASD, and emphasize the importance of the THC component for alleviating deficits in repetitive and social behaviors in ASD.

CB1 Cannabinoid Receptor Signaling and Biased Signaling

The CB1 cannabinoid receptor is a G-protein coupled receptor highly expressed throughout the central nervous system that is a promising target for the treatment of various disorders, including anxiety, pain, and neurodegeneration. Despite the wide therapeutic potential of CB1, the development of drug candidates is hindered by adverse effects, rapid tolerance development, and abuse potential. Ligands that produce biased signaling—the preferential activation of a signaling transducer in detriment of another—have been proposed as a strategy to dissociate therapeutic and adverse effects for a variety of G-protein coupled receptors. However, biased signaling at the CB1 receptor is poorly understood due to a lack of strongly biased agonists. Here, we review studies that have investigated the biased signaling profile of classical cannabinoid agonists and allosteric ligands, searching for a potential therapeutic advantage of CB1 biased signaling in different pathological states. Agonist and antagonist bound structures of CB1 and proposed mechanisms of action of biased allosteric modulators are used to discuss a putative molecular mechanism for CB1 receptor activation and biased signaling. Current studies suggest that allosteric binding sites on CB1 can be explored to yield biased ligands that favor or hinder conformational changes important for biased signaling.

The chemistry and toxicology of vaping

Vaping is the process of inhaling and exhaling an aerosol produced by an e-cigarette, vape pen, or personal aerosolizer. When the device contains nicotine, the Food and Drug Administration (FDA) lists the product as an electronic nicotine delivery system or ENDS device. Similar electronic devices can be used to vape cannabis extracts. Over the past decade, the vaping market has increased exponentially, raising health concerns over the number of people exposed and a nationwide outbreak of cases of severe, sometimes fatal, lung dysfunction that arose suddenly in otherwise healthy individuals. In this review, we discuss the various vaping technologies, which are remarkably diverse, and summarize the use prevalence in the U.S. over time by youths and adults. We examine the complex chemistry of vape carrier solvents, flavoring chemicals, and transformation products. We review the health effects from epidemiological and laboratory studies and, finally, discuss the proposed mechanisms underlying some of these health effects. We conclude that since much of the research in this area is recent and vaping technologies are dynamic, our understanding of the health effects is insufficient. With the rapid growth of ENDS use, consumers and regulatory bodies need a better understanding of constituent-dependent toxicity to guide product use and regulatory decisions.

Control of exploration, motor coordination and amphetamine sensitization by cannabinoid CB1 receptors expressed in medium spiny neurons

Activation of cannabinoid 1 receptors (CB₁ R) modulates multiple behaviours, including exploration, motor coordination and response to psychostimulants. It is known that CB₁ R expressed by either excitatory or inhibitory neurons mediates different behavioural responses to CB₁ R activation, yet the involvement of CB₁ R expressed by medium spiny neurons (MSNs), the neuronal subpopulation that expresses the highest level of CB₁ R in the CNS, remains unknown. We report a new genetically modified mouse line that expresses functional CB₁ R in MSN on a CB₁ R knockout (KO) background (CB₁ R_(MSN) mice). The absence of cannabimimetic responses measured in CB₁ R KO mice was not rescued in CB₁ R_(MSN) mice, nor was decreased spontaneous locomotion, impaired instrumental behaviour or reduced amphetamine-triggered hyperlocomotion measured in CB₁ R KO mice. Significantly, reduced novel environment exploration of an open field and absence of amphetamine sensitization (AS) measured in CB₁ R KO mice were fully rescued in CB₁ R_(MSN) mice. Impaired motor coordination in CB₁ R KO mice measured on the Rotarod was partially rescued in CB₁ R_(MSN) mice. Thus, CB₁ R expressed by MSN control exploration, motor coordination, and AS. Our study demonstrates a new functional roles for cell specific CB₁ R expression and their causal link in the control of specific behaviors.

Δ9 -Tetrahydrocannabinol promotes functional remyelination in the mouse brain

BACKGROUND AND PURPOSE

Research on demyelinating disorders aims to find novel molecules that are able to induce oligodendrocyte precursor cell differentiation to promote central nervous system remyelination and functional recovery. Δ⁹ -Tetrahydrocannabinol (THC), the most prominent active constituent of the hemp plant Cannabis sativa, confers neuroprotection in animal models of demyelination. However, the possible effect of THC on myelin repair has never been studied.

EXPERIMENTAL APPROACH

By using oligodendroglia-specific reporter mouse lines in combination with two models of toxin-induced demyelination, we analysed the effect of THC on the processes of oligodendrocyte regeneration and functional remyelination.

KEY RESULTS

We show that THC administration enhanced oligodendrocyte regeneration, white matter remyelination and motor function recovery. THC also promoted axonal remyelination in organotypic cerebellar cultures. THC remyelinating action relied on the induction of oligodendrocyte precursor differentiation upon cell cycle exit and via CB₁ cannabinoid receptor activation.

CONCLUSIONS AND IMPLICATIONS

Overall, our study identifies THC administration as a promising pharmacological strategy aimed to promote functional CNS remyelination in demyelinating disorders.

Be cool to be far: Exploiting hibernation for space exploration

In mammals, torpor/hibernation is a state that is characterized by an active reduction in metabolic rate followed by a progressive decrease in body temperature. Torpor was successfully mimicked in non-hibernators by inhibiting the activity of neurons within the brainstem region of the Raphe Pallidus, or by activating the adenosine A1 receptors in the brain. This state, called synthetic torpor, may be exploited for many medical applications, and for space exploration, providing many benefits for biological adaptation to the space environment, among which an enhanced protection from cosmic rays. As regards the use of synthetic torpor in space, to fully evaluate the degree of physiological advantage provided by this state, it is strongly advisable to move from Earth-based experiments to 'in the field' tests, possibly on board the International Space Station.

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.

Sex-dependent pharmacological profiles of the synthetic cannabinoid MMB-Fubinaca

Synthetic cannabinoids have emerged as novel psychoactive substances with damaging consequences for public health. They exhibit high affinity at the cannabinoid type-1 (CB₁ ) receptor and produce similar and often more potent effects as other CB₁ receptor agonists. However, we are still far from a complete pharmacological understanding of these compounds. In this study, by using behavioral, molecular, pharmacological, and electrophysiological approaches, we aimed at characterizing several in vitro and in vivo pharmacological effects of the synthetic cannabinoid MMB-Fubinaca (also known as AMB-Fubinaca or FUB-AMB), a particular synthetic cannabinoid. MMB-Fubinaca stimulates CB₁ receptor-mediated functional coupling to G-proteins in mouse and human brain preparations in a similar manner as the CB₁ receptor agonist WIN55,512-2 but with a much greater potency. Both drugs similarly activate the CB₁ receptor-dependent extracellular signal-regulated kinase (ERK) pathway. Notably, in vivo administration of MMB-Fubinaca in mice induced greater behavioral and electrophysiological effects in male than in female mice in a CB₁ receptor-dependent manner. Overall, these data provide a solid pharmacological profiling of the effects of MMB-Fubinaca and important information about the mechanisms of action underlying its harmful impact in humans. At the same time, they reinforce the significant sexual dimorphism of cannabinoid actions, which will have to be taken into account in future animal and clinical studies.

Appetitive, antinociceptive, and hypothermic effects of vaped and injected Δ-9-tetrahydrocannabinol (THC) in rats: exposure and dose-effect comparisons by strain and sex

Advances in drug vapor exposure systems have enabled evaluation of Δ-9-tetrahydrocannabinol (THC) vapor effects in laboratory animals. The purpose of this study was to 1) establish a range of parameters of THC vapor exposure in rats sufficient to produce a behavioral dose-effect curve in a battery of tasks sensitive to THC; and 2) to investigate sex differences in the effects of THC vapor exposure and THC injection (intraperitoneal, IP) on these behaviors in two strains of outbred rats. Male and female Sprague Dawley and Wistar rats (N = 22, 5-6/sex per group) received THC via passive vapor exposure (200 mg/mL; 5 conditions) and IP injection (1-20 mg/kg) in a within subject design. The effects of vaped and injected THC on appetite was determined using progressive ratio responding for food pellets. THC effects on nociception, measured using the tail withdrawal assay, and body temperature were also assessed during a 5-h test period for evaluation of time course of effects. Plasma THC concentrations were assessed after THC vapor and 10 mg/kg IP THC. THC vapor produced exposure-related increases and decreases in motivation to obtain food under the progressive ratio schedule. IP THC (3-20 mg/kg) reduced breakpoints. Vaped and injected THC produced exposure and dose-dependent antinociception and hypothermia. Sex and strain differences in THC effects were also observed. Plasma THC concentrations were higher after 10 mg/kg IP THC (152 ng/mL) compared to the highest vapor exposure condition tested (38 ng/mL), but magnitude of behavioral effects were comparable. THC vapor exposure produced reliable, dose orderly effects on food-maintained behavior, nociception, and body temperature that are comparable to effects of IP THC, although there were differences in the time course of behavioral outcomes.

Inhibition of striatonigral autophagy as a link between cannabinoid intoxication and impairment of motor coordination

The use of cannabis is rapidly expanding worldwide. Thus, innovative studies aimed to identify, understand and potentially reduce cannabis-evoked harms are warranted. Here, we found that Δ⁹-tetrahydrocannabinol, the psychoactive ingredient of cannabis, disrupts autophagy selectively in the striatum, a brain area that controls motor behavior, both in vitro and in vivo. Boosting autophagy, either pharmacologically (with temsirolimus) or by dietary intervention (with trehalose), rescued the Δ⁹-tetrahydrocannabinol-induced impairment of motor coordination in mice. The combination of conditional knockout mouse models and viral vector-mediated autophagy-modulating strategies in vivo showed that cannabinoid CB₁ receptors located on neurons belonging to the direct (striatonigral) pathway are required for the motor-impairing activity of Δ⁹-tetrahydrocannabinol by inhibiting local autophagy. Taken together, these findings identify inhibition of autophagy as an unprecedented mechanistic link between cannabinoids and motor performance, and suggest that activators of autophagy might be considered as potential therapeutic tools to treat specific cannabinoid-evoked behavioral alterations.

Translation of in vitro cannabinoid 1 receptor agonist activity to in vivo pharmacodynamic endpoints

INTRODUCTION

Building an understanding of in vivo efficacy based on the evaluation of in vitro affinity or potency is critical in expediting early decision making in drug discovery and can significantly reduce the need for animal studies. The aim of the present study was to understand the translation of in vitro to in vivo endpoints for the cannabinoid receptor 1 (CB1).

METHODS

Using a selection of CB1 agonists we describe an evaluation of in vitro to in vivo translation comparing in vitro receptor affinity or functional potency, using both cAMP and β-arrestin endpoints, to various in vivo CB1 agonist-associated endpoints.

RESULTS

We demonstrate that in vitro CB1 agonism significantly correlates with the CB1-induced cue in the drug discrimination model in vivo, but not with other purported CB1 agonist-mediated in vivo endpoints, including hypothermia and sedation. Thus, these data challenge common perceptions regarding CB1 agonist-induced tetrad effects in rodents.

DISCUSSION

This work exemplifies how in vitro profiling of receptor affinity or potency can predict in vivo pharmacodynamic effects, using the CB1 as an example system. The translatability of in vitro activity to in vivo efficacy allows for the ability to rapidly contextualize off-target CB1 in vitro findings, allowing clear and rapid definition of the risk posed by such activity without the need for extensive animal studies. This has significant implications in terms of early decision making in drug discovery and reducing the use of animals in research, while also outlining a template for expanding the approach for additional targets.

An Open Source Automated Bar Test for Measuring Catalepsy in Rats

Catalepsy bar tests are widely used to measure the failure to correct an imposed posture resulting from muscular rigidity. Procedures for measuring catalepsy vary greatly in the published literature, but one commonly used test measures the time it takes for a rodent to remove one or both of its forelimbs from a bar. The following paper describes an affordable, adjustable, open-source bar test that automatically measures and logs the time it takes for a rat to remove itself from a bar. While commercially available automated bar tests are prohibitively expensive, requiring proprietary software and hardware to operate, the proposed apparatus runs on an Arduino-based microcontroller making it low-cost and customizable. This 3D-printed design costs less than 65 United States dollars to build and is simple to assemble and operate. The beam-break sensor design also eliminates many of the pitfalls of the “complete-the-circuit”-based approach to recording catalepsy. The paper further describes the successful validation of the design using adult male rats injected with different doses of haloperidol to demonstrate a dose-dependent cataleptic effect. This design provides a versatile, low-cost solution to standardizing and automating measurement of catalepsy in rodents.

Cannabis sativa: Much more beyond Δ9-tetrahydrocannabinol

Cannabis is the most used illicit drug worldwide and its medicinal use is under discussion, being regulated in several countries. However, the psychotropic effects of Δ⁹-tetrahydrocannabinol (THC), the main psychoactive compound of Cannabis sativa, are of concern. Thus, the interest in the isolated constituents without psychotropic activity, such as cannabidiol (CBD) and cannabidivarin (CBDV) is growing. CBD and CBDV are lipophilic molecules with poor oral bioavailability and are mainly metabolized by cytochrome P450 (CYP450) enzymes. The pharmacodynamics of CBD is the best explored, being able to interact with diverse molecular targets, like cannabinoid receptors, G protein-coupled receptor-55, transient receptor potential vanilloid 1 channel and peroxisome proliferator-activated receptor-γ. Considering the therapeutic potential, several clinical trials are underway to study the efficacy of CBD and CBDV in different pathologies, such as neurodegenerative diseases, epilepsy, autism spectrum disorders and pain conditions. The anti-cancer properties of CBD have also been demonstrated by several pre-clinical studies in different types of tumour cells. Although less studied, CBDV, a structural analogue of CBD, is receiving attention in the last years. CBDV exhibits anticonvulsant properties and, currently, clinical trials are underway for the treatment of autism spectrum disorders. Despite the benefits of these phytocannabinoids, it is important to highlight their potential interference with relevant physiologic mechanisms. In fact, CBD interactions with CYP450 enzymes and with drug efflux transporters may have serious consequences when co-administered with other drugs. This review summarizes the therapeutic advances of CBD and CBDV and explores some aspects of their pharmacokinetics, pharmacodynamics and possible interactions. Moreover, it also highlights the therapeutic potential of CBD and CBDV in several medical conditions and clinical applications.

Isolation of a High-Affinity Cannabinoid for the Human CB1 Receptor from a Medicinal Cannabis sativa Variety: Δ9-Tetrahydrocannabutol, the Butyl Homologue of Δ9-Tetrahydrocannabinol

The butyl homologues of Δ⁹-tetrahydrocannabinol, Δ⁹-tetrahydrocannabutol (Δ⁹-THCB), and cannabidiol, cannabidibutol (CBDB), were isolated from a medicinal Cannabis sativa variety (FM2) inflorescence. Appropriate spectroscopic and spectrometric characterization, including NMR, UV, IR, ECD, and HRMS, was carried out on both cannabinoids. The chemical structures and absolute configurations of the isolated cannabinoids were confirmed by comparison with the spectroscopic data of the respective compounds obtained by stereoselective synthesis. The butyl homologue of Δ⁹-THC, Δ⁹-THCB, showed an affinity for the human CB1 (K_i = 15 nM) and CB2 receptors (K_i = 51 nM) comparable to that of (-)-trans-Δ⁹-THC. Docking studies suggested the key bonds responsible for THC-like binding affinity for the CB1 receptor. The formalin test in vivo was performed on Δ⁹-THCB in order to reveal possible analgesic and anti-inflammatory properties. The tetrad test in mice showed a partial agonistic activity of Δ⁹-THCB toward the CB1 receptor.

A novel phytocannabinoid isolated from Cannabis sativa L. with an in vivo cannabimimetic activity higher than Δ9-tetrahydrocannabinol: Δ9-Tetrahydrocannabiphorol

(-)-Trans-Δ9-tetrahydrocannabinol (Δ9-THC) is the main compound responsible for the intoxicant activity of Cannabis sativa L. The length of the side alkyl chain influences the biological activity of this cannabinoid. In particular, synthetic analogues of Δ9-THC with a longer side chain have shown cannabimimetic properties far higher than Δ9-THC itself. In the attempt to define the phytocannabinoids profile that characterizes a medicinal cannabis variety, a new phytocannabinoid with the same structure of Δ9-THC but with a seven-term alkyl side chain was identified. The natural compound was isolated and fully characterized and its stereochemical configuration was assigned by match with the same compound obtained by a stereoselective synthesis. This new phytocannabinoid has been called (-)-trans-Δ9-tetrahydrocannabiphorol (Δ9-THCP). Along with Δ9-THCP, the corresponding cannabidiol (CBD) homolog with seven-term side alkyl chain (CBDP) was also isolated and unambiguously identified by match with its synthetic counterpart. The binding activity of Δ9-THCP against human CB1 receptor in vitro (Ki = 1.2 nM) resulted similar to that of CP55940 (Ki = 0.9 nM), a potent full CB1 agonist. In the cannabinoid tetrad pharmacological test, Δ9-THCP induced hypomotility, analgesia, catalepsy and decreased rectal temperature indicating a THC-like cannabimimetic activity. The presence of this new phytocannabinoid could account for the pharmacological properties of some cannabis varieties difficult to explain by the presence of the sole Δ9-THC.

Lipokines and Thermogenesis

Adaptive thermogenesis is a catabolic process that consumes energy-storing molecules and expends that energy as heat in response to environmental changes. This process occurs primarily in brown and beige adipose tissue. Thermogenesis is regulated by many factors, including lipid derived paracrine and endocrine hormones called lipokines. Recently, technologic advances for identifying new lipid biomarkers of thermogenic activity have shed light on a diverse set of lipokines that act through different pathways to regulate energy expenditure. In this review, we highlight a few examples of lipokines that regulate thermogenesis. The biosynthesis, regulation, and effects of the thermogenic lipokines in several families are reviewed, including oloeylethanolamine, endocannabinoids, prostaglandin E2, and 12,13-diHOME. These thermogenic lipokines present potential therapeutic targets to combat states of excess energy storage, such as obesity and related metabolic disorders.

Dark Classics in Chemical Neuroscience: Δ9-Tetrahydrocannabinol

Cannabis ( Cannabis sativa) is the most widely used illicit drug in the world, with an estimated 192 million users globally. The main psychoactive component of cannabis is (-)- trans-Δ⁹-tetrahydrocannabinol (Δ⁹-THC), a compound with a diverse range of pharmacological actions. The unique and distinctive intoxication caused by Δ⁹-THC primarily reflects partial agonist action at central cannabinoid type 1 (CB₁) receptors. Δ⁹-THC is an approved therapeutic treatment for a range of conditions, including chronic pain, chemotherapy-induced nausea and vomiting, and multiple sclerosis, and is being investigated in indications such as anorexia nervosa, agitation in dementia, and Tourette's syndrome. It is available as a regulated pharmaceutical in products such as Marinol, Sativex, and Namisol as well as in an ever-increasing range of unregistered medicinal and recreational cannabis products. While cannabis is an ancient medicament, contemporary use is embroiled in legal, scientific, and social controversy, much of which relates to the potential hazards and benefits of Δ⁹-THC itself. Robust contemporary debate surrounds the therapeutic value of Δ⁹-THC in different diseases, its capacity to produce psychosis and cognitive impairment, and the addictive and "gateway" potential of the drug. This review will provide a profile of the chemistry, pharmacology, and therapeutic uses of Δ⁹-THC as well as the historical and societal import of this unique, distinctive, and ubiquitous psychoactive substance.

Aging circadian rhythms and cannabinoids

Numerous aspects of mammalian physiology exhibit cyclic daily patterns known as circadian rhythms. However, studies in aged humans and animals indicate that these physiological rhythms are not consistent throughout the life span. The simultaneous development of disrupted circadian rhythms and age-related impairments suggests a shared mechanism, which may be amenable to therapeutic intervention. Recently, the endocannabinoid system has emerged as a complex signaling network, which regulates numerous aspects of circadian physiology relevant to the neurobiology of aging. Agonists of cannabinoid receptor-1 (CB1) have consistently been shown to decrease neuronal activity, core body temperature, locomotion, and cognitive function. Paradoxically, several lines of evidence now suggest that very low doses of cannabinoids are beneficial in advanced age. One potential explanation for this phenomenon is that these drugs exhibit hormesis-a biphasic dose-response wherein low doses produce the opposite effects of higher doses. Therefore, it is important to determine the dose-, age-, and time-dependent effects of these substances on the regulation of circadian rhythms and other processes dysregulated in aging. This review highlights 3 fields-biological aging, circadian rhythms, and endocannabinoid signaling-to critically assess the therapeutic potential of endocannabinoid modulation in aged individuals. If the hormetic properties of exogenous cannabinoids are confirmed, we conclude that precise administration of these compounds may bidirectionally entrain central and peripheral circadian clocks and benefit multiple aspects of aging physiology.

Progress in brain cannabinoid CB2 receptor research: From genes to behavior

The type 2 cannabinoid receptor (CB2R) was initially regarded as a peripheral cannabinoid receptor. However, recent technological advances in gene detection, alongside the availability of transgenic mouse lines, indicate that CB2Rs are expressed in both neurons and glial cells in the brain under physiological and pathological conditions, and are involved in multiple functions at cellular and behavioral levels. Brain CB2Rs are inducible and neuroprotective via up-regulation in response to various insults, but display species differences in gene and receptor structures, CB2R expression, and receptor responses to various CB2R ligands. CB2R transcripts also differ between the brain and spleen. In the brain, CB2A is the major transcript isoform, while CB2A and CB2B transcripts are present at higher levels in the spleen. These new findings regarding brain versus spleen CB2R isoforms may in part explain why early studies failed to detect brain CB2R gene expression. Here, we review evidence supporting the expression and function of brain CB2R from gene and receptor levels to cellular functioning, neural circuitry, and animal behavior.