Cannabinoid Receptor Type 1 and Its Role as an Analgesic: An Opioid Alternative?

 Publication Cover“Understanding how the body regulates pain is fundamental to develop rational strategies to combat the growing prevalence of chronic pain states, opioid dependency, and the increased financial burden to the medical care system.

Pain is the most prominent reason why Americans seek medical attention and extensive literature has identified the importance of the endocannabinoid pathway in controlling pain. Modulation of the endocannabinoid system offers new therapeutic opportunities for the selective control of excessive neuronal activity in several pain conditions (acute, inflammatory, chronic, and neuropathic).

Cannabinoids have a long history of medicinal use and their analgesic properties are well documented; however, there are major impediments to understanding cannabinoid pain modulation.

One major issue is the presence of psychotropic side effects associated with D9-tetrahydrocannabinol (THC) or synthetic derivatives, which puts an emphatic brake on their use. This dose-limiting effect prevents the appropriate degree of analgesia .

Animal studies have shown that the psychotropic effects are mediated via brain cannabinoid type 1 (CB1) receptors, while analgesic activity in chronic pain states may be mediated via CB1R action in the spinal cord, brainstem, peripheral sensory neurons, or immune cells.

The development of appropriate therapies is incumbent on our understanding of the role of peripheral versus central endocannabinoid-driven analgesia. Recent physiological, pharmacological, and anatomical studies provide evidence that one of the main roles of the endocannabinoid system is the regulation of gamma-aminobutyric acid (GABA) and/or glutamate release.

This article will review this evidence in the context of its implications for pain. We first provide a brief overview of CB1R’s role in the regulation of nociception, followed by a review of the evidence that the peripheral endocannabinoid system modulates nociception.

We then look in detail at regulation of central-mediated analgesia, followed up with evidence that cannabinoid mediated modulation of pain involves modulation of GABAergic and glutamatergic neurotransmission in key brain regions. Finally, we discuss cannabinoid action on non-neuronal cells in the context of inflammation and direct modulation of neurons.

This work stands to reveal long-standing controversies in the cannabinoid analgesia area that have had an impact on failed clinical trials and implementation of therapeutics targeting this system.”

https://www.ncbi.nlm.nih.gov/pubmed/31596190

https://www.tandfonline.com/doi/abs/10.1080/15504263.2019.1668100?journalCode=wjdd20

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The effect of cannabis laws on opioid use.

International Journal of Drug Policy“Many Americans rely on opioids at varying dosages to help ameliorate their suffering. However, empirical evidence is mounting that opioids are ineffective at controlling non-cancer related chronic pain, and many argue the strategies meant to relieve patient suffering are contributing to the growing opioid epidemic.

Concurrently, several states now allow the use of medical cannabis to treat a variety of medical conditions, including chronic pain. Needing more exploration is the impact of cannabis laws on general opioid reliance and whether chronic pain sufferers are opting to use cannabis medicinally instead of opioids.

METHODS:

This study investigates the effect of Medical Marijuana Laws (MML)s on opioid use and misuse controlling for a number of relevant factors using data from several years of the National Survey on Drug Use and Health and multivariate logistic regression and longitudinal analysis strategies.

RESULTS:

Results provide evidence that MMLs may be effective at reducing opioid reliance as survey respondents living in states with medical cannabis legislation are much less apt to report using opioid analgesics than people living in states without such laws, net other factors. Results further indicate that the presence of medicinal cannabis legislation appears to have no influence over opioid misuse.

CONCLUSION:

MMLs may ultimately serve to attenuate the consequences of opioid overreliance.”

https://www.ncbi.nlm.nih.gov/pubmed/31590091

https://www.sciencedirect.com/science/article/abs/pii/S0955395919302567?via%3Dihub

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Role of Cannabinoids and Terpenes in Cannabis-Mediated Analgesia in Rats.

View details for Cannabis and Cannabinoid Research cover image

“Cannabis sativa has been used for centuries in treating pain. However, the analgesic role of many of its constituents including terpenes is unknown. This research examined the contributions of terpenes (volatile oil) and cannabinoids in cannabis-mediated analgesia in rats.

Methods: Animals received intraperitoneal administration of either vehicle, 10.0 or 18.0 mg/kg morphine, or various doses of the extract without terpenes, isolated terpenes, Δ9-tetrahydrocannabinol (THC), or the full extract. Thirty minutes later animals were tested on hotplate and tail-flick tests of thermal nociception. One week later, rats received a second administration of test articles and were tested 30 min later in the abdominal writhing test of inflammatory nociception.

Results: In the thermal assays, hotplate and tail-flick latencies for morphine-treated rats were dose dependent and significantly higher than vehicle-treated animals. All the cannabinoid compounds except for the isolated terpenes produced dose-dependent increases in hotplate and tail-flick latencies. In the inflammatory nociceptive assay, animals treated with vehicle and isolated terpenes demonstrated increased abdominal writhing, whereas all the cannabinoid compounds significantly decreased abdominal writhing responses.

Conclusions: Overall, THC alone produced robust analgesia equivalent to the full cannabis extract, whereas terpenes alone did not produce analgesia. These data suggest the analgesic activity of cannabis is largely mediated by THC, whereas terpenes alone do not cause alterations in cannabis-mediated analgesia.”

https://www.ncbi.nlm.nih.gov/pubmed/31579834

“The work herein demonstrates that cannabis extracts can not only produce robust analgesia without the terpene-containing volatile oils, but isolated THC appears to be all that is required to produce such effects.”

https://www.liebertpub.com/doi/10.1089/can.2018.0054

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Cannabinoids, Pain, and Opioid Use Reduction: The Importance of Distilling and Disseminating Existing Data.

View details for Cannabis and Cannabinoid Research cover image“The high prevalence of chronic pain conditions combined with an over-reliance on opioid prescriptions has resulted in an opioid epidemic and a desperate need for solutions.

There is some debate about whether cannabis might play a role in addressing chronic pain conditions as well as the opioid epidemic.

Recent surveys suggest that a large number of people are using cannabis as a treatment for pain and to reduce use of opioids, and cannabis-derived products demonstrate at least modest efficacy in the treatment of pain in randomized controlled trials.

In addition, surveillance studies from countries that have approved the use of Sativex, which is a cannabis-based product, have demonstrated that a combination of Δ9-tetrahydrocannabinol and cannabidiol has low potential for harm, is well tolerated, and is helpful to patients.

Given the number of people in the United States who are already using cannabis to manage pain and opioid use in state-regulated markets, it is imperative to conduct additional research in these areas, and to disseminate information on how to minimize harm and maximize any benefits of using cannabinoids to mitigate pain and reduce opioid use.

The purpose of this article is to call attention to the fact that cannabis is being used in the management of chronic pain. Thus, this article also provides a set of guidelines on how to approach using cannabis to treat pain.”

https://www.ncbi.nlm.nih.gov/pubmed/31579833

https://www.liebertpub.com/doi/10.1089/can.2018.0052

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Endogenous cannabinoid modulation of restraint stress-induced analgesia in thermal nociception.

Journal of Neurochemistry banner“It is thought that endogenous cannabinoids have a role in the analgesia induced by specific forms of stress.

We examined if the role of endogenous cannabinoids is also dependent upon the mode of nociception, and whether this could be altered by drugs which block their enzymatic degradation.

These findings indicate the role of endocannabinoids in stress-induced analgesia differs with the type of thermal pain behaviour. However, by inhibiting their breakdown, endocannabinoids can be recruited to substitute for endogenous opioid signalling when their activity is blocked, indicating a degree of redundancy between opioid and cannabinoid systems.

Together these data suggest targeting endocannabinoid breakdown could provide an alternative, or adjuvant to mainstream analgesics such as opioids.”

https://www.ncbi.nlm.nih.gov/pubmed/31571215

https://onlinelibrary.wiley.com/doi/abs/10.1111/jnc.14884

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Targeting Cannabinoid 1 and Delta Opioid Receptor Heteromers Alleviates Chemotherapy-Induced Neuropathic Pain.

“Cannabinoid 1 (CB1R) and delta opioid receptors (DOR) associate to form heteromers that exhibit distinct pharmacological properties.

Not much is known about CB1R-DOR heteromer location or signaling along the pain circuit in either animal models or patients with chemotherapy-induced peripheral neuropathy (CIPN).

Here, we use paclitaxel to induce CIPN in mice and confirm the development of mechanical allodynia.

Together, these results imply that CB1R-DOR heteromers upregulated during CIPN-associated mechanical allodynia could serve as a potential target for treatment of neuropathic pain including CIPN.”

https://www.ncbi.nlm.nih.gov/pubmed/31565698

https://pubs.acs.org/doi/10.1021/acsptsci.9b00008

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Comparative studies of endocannabinoid modulation of pain.

Philosophical Transactions of the Royal Society B: Biological Sciences cover image

“Cannabinoid-based therapies have long been used to treat pain, but there remain questions about their actual mechanisms and efficacy. From an evolutionary perspective, the cannabinoid system would appear to be highly conserved given that the most prevalent endogenous cannabinoid (endocannabinoid) transmitters, 2-arachidonyl glycerol and anandamide, have been found throughout the animal kingdom, at least in the species that have been analysed to date. This review will first examine recent findings regarding the potential conservation across invertebrates and chordates of the enzymes responsible for endocannabinoid synthesis and degradation and the receptors that these transmitters act on. Next, comparisons of how endocannabinoids modulate nociception will be examined for commonalities between vertebrates and invertebrates, with a focus on the medicinal leech Hirudo verbana. Evidence is presented that there are distinct, evolutionarily conserved anti-nociceptive and pro-nociceptive effects. The combined studies across various animal phyla demonstrate the utility of using comparative approaches to understand conserved mechanisms for modulating nociception. This article is part of the Theo Murphy meeting issue ‘Evolution of mechanisms and behaviour important for pain’.”

https://www.ncbi.nlm.nih.gov/pubmed/31544609

https://royalsocietypublishing.org/doi/10.1098/rstb.2019.0279

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Medical cannabis for chronic pain: can it make a difference in pain management?

 “Globally, chronic pain is a major therapeutic challenge and affects more than 15% of the population. As patients with painful terminal diseases may face unbearable pain, there is a need for more potent analgesics.

Although opioid-based therapeutic agents received attention to manage severe pain, their adverse drug effects and mortality rate associated with opioids overdose are the major concerns.

Evidences from clinical trials showed therapeutic benefits of cannabis, especially delta-9-tetrahydrocannabinol and cannabinoids reduced neuropathic pain intensity in various conditions. Also, there are reports on using combination cannabinoid therapies for chronic pain management.

The association of cannabis dependence and addiction has been discussed much and the reports mentioned that it can be comparatively lower than other substances such as nicotine and alcohol.

More countries have decided to legalise the medicinal use of cannabis and marijuana.

Healthcare professionals should keep themselves updated with the changing state of medical cannabis and its applications.”

https://www.ncbi.nlm.nih.gov/pubmed/31535218

https://link.springer.com/article/10.1007%2Fs00540-019-02680-y

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The effects of cannabis, cannabinoids, and their administration routes on pain control efficacy and safety: A systematic review and network meta-analysis.

“To determine the effects of cannabis, cannabinoids, and their administration routes on pain and adverse euphoria events.

Randomized controlled trials investigating the effects of cannabis or cannabinoids on pain reduction.

RESULTS:

A total of 25 studies involving 2270 patients were included. We found that delta-9-tetrahydrocannabinol/cannabidiol (THC/CBD) (oromucosal route), THC (oromucosal route), and standardized dried cannabis (with THC; SCT; inhalation route) could reduce neuropathic pain score (SMD -0.41, 95% CI -0.7 to -0.1; -0.61, 95% CI -1.2 to -0.02; and -0.77, 95% CI -1.4 to -0.2; respectively). For nociceptive pain, only standardized cannabis extract (with THC; SCET) via oral route could reduce pain score (SMD -1.8, 95% C; -2.4 to -1.2). In cancer pain, THC/CBD via oromucosal route and THC via oral or oromucosal route could reduce pain score (SMD -0.7, 95% CI -1.2 to -0.2; and -2.1, 95% CI -2.8 to -1.4; respectively). No study was observed for THC/CBD via oral route or inhalation or THC via inhalation for cancer and nociceptive pain, SCET via oromucosal route or inhalation for neuropathic and cancer pain, THC via oromucosal route for nociceptive pain, and SCT via oromucosal or oral route for neuropathic, cancer, and nociceptive pain. Statistically significant increased risks of euphoria were observed in THC/CBD (oromucosal), THC (oromucosal), and SCT (inhalation).

CONCLUSION:

The use of cannabis and cannabinoids via certain administration routes could reduce different types of pain. Product developers could consider our findings as part of their product design so that the effective route of cannabis and cannabinoids for pain control can be achieved.”

https://www.ncbi.nlm.nih.gov/pubmed/31495691

https://www.japha.org/article/S1544-3191(19)30353-X/fulltext

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Insights into biased signaling at cannabinoid receptors: synthetic cannabinoid receptor agonists.

Biochemical Pharmacology“Cannabinoid receptors type 1 (CB1) and type 2 (CB2) are promising targets for a number of diseases, including obesity, neuropathic pain, and multiple sclerosis, among others.

Upon ligand-mediated activation of these receptors, multiple receptor conformations could be stabilized, resulting in a complex pattern of possible intracellular effects. Although numerous compounds have been developed and widely used to target cannabinoid receptors, their mode of action and signaling properties are often only poorly characterized.

From a drug development point of view, unraveling the underlying complex signaling mechanism could offer the possibility to generate medicines with the desired therapeutic profile.

Recently, an increased interest has emerged for the development of agonists that are signaling pathway-selective and thereby do not evoke on-target adverse effects. This phenomenon, in which specific pathways are preferred upon receptor activation by certain ligands, is also known as ‘biased signaling’.

For a particular group of cannabinoid receptor ligands (i.e. CB1/CB2 agonists), namely the synthetic cannabinoid receptor agonists (SCRAs), the research on biased signaling is still in its infancy and interesting outcomes are only recently being revealed.

Therefore, this review aims at providing insights into the recent knowledge about biased agonism mediated by SCRAs so far. In addition, as these outcomes are obtained using a distinct panel of functional assays, the accompanying difficulties and challenges when comparing functional outcomes are critically discussed. Finally, some guidance on the conceptualization of ideal in vitro assays for the detection of SCRA-mediated biased agonism, which is also relevant for compounds belonging to other chemical classes, is provided.”

https://www.ncbi.nlm.nih.gov/pubmed/31472128

https://www.sciencedirect.com/science/article/abs/pii/S0006295219303132?via%3Dihub

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