Cannabidiol Is a Potential Therapeutic for the Affective-Motivational Dimension of Incision Pain in Rats

A journey through cannabidiol in Parkinson's disease

Parkinson's disease is a chronic neurodegenerative disorder with no known cure characterized by motor symptoms such as tremors, rigidity, bradykinesia (slowness of movement), and postural instability. Non-motor symptoms like cognitive impairment, mood disturbances, and sleep disorders often accompany the disease. Pharmacological treatments for these symptoms are limited and frequently induce significant adverse reactions, underscoring the necessity for appropriate treatment options. Cannabidiol is a phytocannabinoid devoid of the euphoric and cognitive effects of tetrahydrocannabinol. The study of cannabidiol's pharmacological effects has increased exponentially in recent years. Preclinical and preliminary clinical studies suggest that cannabidiol holds therapeutic potential for alleviating symptoms of Parkinson's disease, offering neuroprotective, anti-inflammatory, and antioxidant properties. However, knowledge of cannabidiol neuromolecular mechanisms is limited, and its pharmacology, which appears complex, has not yet been fully elucidated. By examining the evidence, this review aims to provide and synthesize scientifically proven evidence for the potential use of cannabidiol as a novel treatment option for Parkinson's disease. We focus on studies that administrated cannabidiol alone. The results of preclinical trials using cannabidiol in models of Parkinson's disease are encouraging. Nevertheless, drawing firm conclusions on the therapeutic efficacy of cannabidiol for patients is challenging. Cannabidiol doses, formulations, outcome measures, and methodologies vary considerably across studies. Though, cannabidiol holds promise as a novel therapeutic option for managing both motor and non-motor symptoms of Parkinson's disease, offering hope for improved quality of life for affected individuals.

Cannabidiol and it fluorinate analog PECS-101 reduces hyperalgesia and allodynia in trigeminal neuralgia via TRPV1 receptors

Trigeminal neuralgia (TN) is an intense and debilitating orofacial pain. The gold standard treatment for TN is carbamazepine. This antiepileptic drug provides pain relief with limited efficacy and side effects. To study the antinociceptive potential of cannabidiol (CBD) and its fluorinated analog PECS-101 (former HUF-101), we induced unilateral chronic constriction injury of the infraorbital nerve (IoN-CCI) in male Wistar rats. Seven days of treatment with CBD (30 mg/kg), PECS-101 (3, 10, and 30 mg/kg), or carbamazepine (10 and 30 mg/kg) reduced allodynia and hyperalgesia responses. Unlike carbamazepine, CBD and PECS-101 did not impair motor activity. The relief of the hypersensitive reactions has been associated with transient receptor potential vanilloid type 1 (TRPV1) modulation in the trigeminal spinal nucleus. CBD (30 mg/kg) and PECS-101 (10 and 30 mg/kg) reversed the increased expression of TRPV1 induced by IoN-CCI in this nucleus. Using a pharmacological strategy, the combination of the selective TRPV1 antagonist (capsazepine-CPZ - 5 mg/kg) with sub-effective doses of CBD (3 and 10 mg/kg) is also able to reverse the IoN-CCI-induced allodynia and hyperalgesia responses. This effect was accompanied by reduced TRPV1 protein expression in the trigeminal spinal nucleus. Our results suggest that CBD and PECS-101 may benefit trigeminal neuralgia without motor coordination impairments. PECS-101 is more potent against the hypernociceptive and motor impairment induced by TN compared to CBD and carbamazepine. The antinociceptive effect of these cannabinoids is partially mediated by TRPV1 receptors in the caudal part of the trigeminal spinal nucleus, the first central station of orofacial pain processing.

Cannabidiol Treatment Shows Therapeutic Efficacy in a Rodent Model of Social Transfer of Pain in Pair-Housed Male Mice

Introduction: Prosocial behavior refers to sharing emotions and sensations such as pain. Accumulated data indicate that cannabidiol (CBD), a nonpsychotomimetic component of the Cannabis sativa plant, attenuates hyperalgesia, anxiety, and anhedonic-like behavior. Nevertheless, the role of CBD in the social transfer of pain has never been evaluated. In this study, we investigated the effects of acute systemic administration of CBD in mice that cohabited with a conspecific animal suffering from chronic constriction injury. Furthermore, we assessed whether repeated CBD treatment decreases hypernociception, anxiety-like behavior, and anhedonic-like responses in mice undergoing chronic constriction injury and whether this attenuation would be socially transferred to the partner. Materials and Methods: Male Swiss mice were Housed in pairs for 28 days. On the 14th day of living together, animals were then divided into two groups: cagemate nerve constriction (CNC), in which one animal of each partner was subjected to sciatic nerve constriction; and cagemate sham (CS), subjected to the same surgical procedure but without suffering nerve constriction. In Experiments 1, 2, and 3 on day 28 of living together, the cagemates (CNC and CS) animals received a single systemic injection (intraperitoneally) of vehicle or CBD (0.3, 1, 10, or 30 mg/kg). After 30 min, the cagemates were subjected to the elevated plusmaze followed by exposure to the writhing and sucrose splash tests. For chronic treatment (Exp. 4), sham and chronic constriction injury animals received a repeated systemic injection (subcutaneous) of vehicle or CBD (10 mg/kg) for 14 days after the sciatic nerve constriction procedure. On days 28 and 29 sham and chronic constriction injury animals and their cagemates were behaviorally tested. Results and Conclusion: Acute CBD administration attenuated anxiety-like behavior, pain hypersensitivity, and anhedonic-like behavior in cagemates that cohabited with a pair in chronic pain. In addition, repeated CBD treatment reversed the anxiety-like behavior induced by chronic pain and enhanced the mechanical withdrawal thresholds in Von Frey filaments and the grooming time in the sucrose splash test. Moreover, repeated CBD treatment effects were socially transferred to the chronic constriction injury cagemates.

Pharmacological Interaction Between Cannabidiol and Tramadol on Experimental Diabetic Neuropathic Pain: An Isobolographic Analysis

Introduction: Diabetic neuropathies are the most prevalent chronic complications of diabetes, characterized by pain and substantial morbidity. Although many drugs have been approved for the treatment of this type of pain, including gabapentin, tramadol (TMD), and classical opioids, it is common to report short-term results or potentially severe side effects. TMD, recommended as a second-line treatment can lead to unwanted side effects. Cannabidiol (CBD) has been gaining attention recently due to its therapeutic properties, including pain management. This study aimed to characterize the pharmacological interaction between CBD and TMD over the mechanical allodynia associated with experimental diabetes using isobolographic analysis. Materials and Methods: After diabetes induction by streptozotocin (STZ), diabetic rats were systemically treated with CBD or TMD alone or in combination (doses calculated based on linear regression of effective dose 40% [ED40]) and had the mechanical threshold evaluated using the electronic Von Frey apparatus. Both experimental and theoretical additive ED40 values (Zmix and Zadd, respectively) were determined for the combination of CBD plus TMD in this model. Results: Acute treatment with CBD (3 or 10 mg/kg) or TMD (2.5, 5, 10, or 20 mg/kg) alone or in combination (0.38+1.65 or 1.14+4.95 mg/kg) significantly improved the mechanical allodynia in STZ-diabetic rats. Isobolographic analysis revealed that experimental ED40 of the combination (Zmix) was 1.9 mg/kg (95% confidence interval [CI]=1.2-2.9) and did not differ from the theoretical additive ED40 2.0 mg/kg (95% CI=1.5-2.8; Zadd), suggesting an additive antinociceptive effect in this model. Conclusions: Using an isobolographic analysis, these results provide evidence of additive pharmacological interaction between CBD and TMD over the neuropathic pain associated with experimental diabetes induced by STZ.

Exploring the therapeutic potential of cannabidiol for sleep deprivation-induced hyperalgesia

Hyperalgesia resulting from sleep deprivation (SD) poses a significant a global public health challenge with limited treatment options. The nucleus accumbens (NAc) plays a crucial role in the modulation of pain and sleep, with its activity regulated by two distinct types of medium spiny neurons (MSNs) expressing dopamine 1 or dopamine 2 (D1-or D2) receptors (referred to as D1-MSNs and D2-MSNs, respectively). However, the specific involvement of the NAc in SD-induced hyperalgesia remains uncertain. Cannabidiol (CBD), a nonpsychoactive phytocannabinoid, has demonstrated analgesic effects in clinical and preclinical studies. Nevertheless, its potency in addressing this particular issue remains to be determined. Here, we report that SD induced a pronounced pronociceptive effect attributed to the heightened intrinsic excitability of D2-MSNs within the NAc in Male C57BL/6N mice. CBD (30 mg/kg, i.p.) exhibited an anti-hyperalgesic effect. CBD significantly improved the thresholds for thermal and mechanical pain and increased wakefulness by reducing delta power. Additionally, CBD inhibited the intrinsic excitability of D2-MSNs both in vitro and in vivo. Bilateral microinjection of the selective D2 receptor antagonist raclopride into the NAc partially reversed the antinociceptive effect of CBD. Thus, these findings strongly suggested that SD activates NAc D2-MSNs, contributing heightened to pain sensitivity. CBD exhibits antinociceptive effects by activating D2R, thereby inhibiting the excitability of D2-MSNs and promoting wakefulness under SD conditions.

Antinociceptive action of cannabidiol on thermal sensitivity and post-operative pain in male and female rats

This study investigated the antinociceptive potential of cannabidiol (CBD) in male and female Wistar rats. The assessment and analysis included tail withdrawal to thermal stimulation (tail flick test) and mechanical allodynia induced by plantar incision injury (von Frey test). CBD reduced acute thermal sensitivity in uninjured animals and post-operative mechanical allodynia in males and females. In the tail flick test, CBD 30 mg/kg i.p. was required to induce antinociception in males. During the proestrus phase, females did not show a statistically significant antinociceptive response to CBD treatment despite a noticeable trend. In contrast, in a separate group of rats tested during the late diestrus phase, antinociception varied with CBD dosage and time. In the post-operative pain model, CBD at 3 mg/kg decreased mechanical allodynia in males. Similarly, this dose reduced allodynia in females during proestrus. However, in females during late diestrus, the lower dose of CBD (0.3 mg/kg) reduced mechanical allodynia, although the latency to onset of the effect was slower (90 min). The effectiveness of a 10-fold lower dose of CBD during the late diestrus stage in females suggests that ovarian hormones can influence the action of CBD. While CBD has potential for alleviating pain in humans, personalized dosing regimens may need to be developed to treat pain in women.

An Overview of Cannabidiol

Cannabidiol (CBD) is one of the most interesting constituents of cannabis, garnering significant attention in the medical community in recent years due to its proven benefit for reducing refractory seizures in pediatric patients. Recent legislative changes in the United States have made CBD readily available to the general public, with up to 14% of adults in the United States having tried it in 2019. CBD is used to manage a myriad of symptoms, including anxiety, pain, and sleep disturbances, although rigorous evidence for these indications is lacking. A significant advantage of CBD over the other more well-known cannabinoid delta-9-tetrahydroncannabinol (THC) is that CBD does not produce a "high." As patients increasingly self-report its use to manage their medical conditions, and as the opioid epidemic continues to drive the quest for alternative pain management approaches, the aims of this narrative review are to provide a broad overview of the discovery, pharmacology, and molecular targets of CBD, its purported and approved neurologic indications, evidence for its analgesic potential, regulatory implications for patients and providers, and future research needs.

Cannabidiol modulates chronic neuropathic pain aversion behavior by attenuation of neuroinflammation markers and neuronal activity in the corticolimbic circuit in male Wistar rats

Chronic neuropathic pain (CNP) is a vast world health problem often associated with the somatosensory domain. This conceptualization is problematic because, unlike most other sensations that are usually affectively neutral and may present emotional, affective, and cognitive impairments. Neuronal circuits that modulate pain can increase or decrease painful sensitivity based on several factors, including context and expectation. The objective of this study was to evaluate whether subchronic treatment with Cannabidiol (CBD; 0.3, 3, and 10 mg/kg intraperitoneal route - i.p., once a day for 3 days) could promote pain-conditioned reversal, in the conditioned place preference (CPP) test, in male Wistar rats submitted to chronic constriction injury (CCI) of the sciatic nerve. Then, we evaluated the expression of astrocytes and microglia in animals treated with CBD through the immunofluorescence technique. Our results demonstrated that CBD promoted the reversal of CPP at 3 and 10 mg/kg. In CCI animals, CBD was able to attenuate the increase in neuronal hyperactivity, measured by FosB protein expression, in the regions of the corticolimbic circuit: anterior cingulate cortex (ACC), complex basolateral amygdala (BLA), granular layer of the dentate gyrus (GrDG), and dorsal hippocampus (DH) - adjacent to subiculum (CA1). CBD also prevented the increased expression of GFAP and IBA-1 in CCI animals. We concluded that CBD effects on CNP are linked to the modulation of the aversive component of pain. These effects decrease chronic neuronal activation and inflammatory markers in regions of the corticolimbic circuit.

Evaluation of cannabidiol nanoparticles and nanoemulsion biodistribution in the central nervous system after intrathecal administration for the treatment of pain

We investigated how the biodistribution of cannabidiol (CBD) within the central nervous system (CNS) is influenced by two different formulations, an oil-in-water (O/W) nanoemulsion and polymer-coated nanoparticles (PCNPs). We observed that both CBD formulations administered were preferentially retained in the spinal cord, with high concentrations reaching the brain within 10 min of administration. The CBD nanoemulsion reached C_max in the brain at 210 ng/g within 120 min (T_max), whereas the CBD PCNPs had a C_max of 94 ng/g at 30 min (T_max), indicating that rapid brain delivery can be achieved through the use of PCNPs. Moreover, the AUC_0-4h of CBD in the brain was increased 3.7-fold through the delivery of the nanoemulsion as opposed to the PCNPs, indicating higher retention of CBD at this site. Both formulations exhibited immediate anti-nociceptive effects in comparison to the respective blank formulations.

The role of cannabinoids in pain modulation in companion animals

The use of cannabinoids in both veterinary and human medicine is controversial for legal and ethical reasons. Nonetheless, the availability and therapeutic use of naturally occurring or synthetic phytocannabinoids, such as Δ9-tetrahydrocannabidiol and cannabidiol, have been the focus of attention in studies regarding their medical uses. This review aims to examine the role of cannabinoids in pain modulation by analyzing scientific findings regarding the signaling pathways of the endocannabinoid system and discussing the analgesic effects of synthetic cannabinoids compared to cannabinoid extracts and the extent and involvement of their receptors. In animals, studies have shown the analgesic properties of these substances and the role of the cannabinoid binding -1 (CB1) and cannabinoid binding -2 (CB2) receptors in the endocannabinoid system to modulate acute, chronic and neuropathic pain. This system consists of three main components: endogenous ligands (anandamide and 2-arachidonoylglycerol), G protein-coupled receptors and enzymes that degrade and recycle the ligands. Evidence suggests that their interaction with CB1 receptors inhibits signaling in pain pathways and causes psychoactive effects. On the other hand, CB2 receptors are associated with anti-inflammatory and analgesic reactions and effects on the immune system. Cannabis extracts and their synthetic derivatives are an effective therapeutic tool that contributes to compassionate pain care and participates in its multimodal management. However, the endocannabinoid system interacts with different endogenous ligands and neurotransmitters, thus offering other therapeutic possibilities in dogs and cats, such is the case of those patients who suffer from seizures or epilepsy, contact and atopic dermatitis, degenerative myelopathies, asthma, diabetes and glaucoma, among other inflammatory diseases. Moreover, these compounds have been shown to possess antineoplastic, appetite-stimulating, and antiemetic properties. Ultimately, the study of the endocannabinoid system, its ligands, receptors, mechanism of action, and signaling, has contributed to the development of research that shows that hemp-derived and their synthetic derivatives are an effective therapeutic alternative in the multimodal management of pain in dogs and cats due to their ability to prevent peripheral and central sensitization.

Sex-dependent differences in the anxiolytic-like effect of cannabidiol in the elevated plus-maze

RATIONALE

Cannabidiol (CBD), the major non-psychoactive constituent of cannabis, has therapeutic potential for the treatment of anxiety. Most preclinical studies investigate only acute effects of CBD and only in males, yet the drug is most likely to be used over a sustained period in clinical practice.

OBJECTIVES

The objectives of this study were to investigate the anxiolytic-like effect of CBD in female rats compared to males and to determine whether the responsiveness of females was influenced by the stage of the estrous cycle.

METHODS

We carried out experiments to compare the effect of CBD in male and female rats in the elevated plus maze (EPM) in response to acute and short-term (4 days) administration through a complete cycle in females.

RESULTS

Male and female rats behaved in a similar manner in the EPM, but females in the late diestrus (LD) phase exhibited more anxiety-like behavior than at other stages, the difference reaching statistical significance compared to proestrus stages. CBD produced anxiolytic-like effects in both sexes, but female rats were responsive only in LD and 10-fold lower dose than males. After sub-chronic (4 days) treatment, responsiveness to CBD was maintained in females in LD, but females in proestrus remained unresponsive to CBD treatment.

CONCLUSIONS

We suggest that there are sex differences in the anxiolytic-like effects of CBD in rats that reflect different underlying mechanisms: based on literature data, gonadal hormone status linked to GABA_A receptor expression in females, and 5-HT_1A receptor activation in males.

Chronic Pain and Cannabidiol in Animal Models: Behavioral Pharmacology and Future Perspectives

The incidence of chronic pain is around 8% in the general population, and its impact on quality of life, mood, and sleep exceeds the burden of its causal pathology. Chronic pain is a complex and multifaceted problem with few effective and safe treatment options. It can be associated with neurological diseases, peripheral injuries or central trauma, or some maladaptation to traumatic or emotional events. In this perspective, animal models are used to assess the manifestations of neuropathy, such as allodynia and hyperalgesia, through nociceptive tests, such as von Frey, Hargreaves, hot plate, tail-flick, Randall & Selitto, and others. Cannabidiol (CBD) has been considered a promising strategy for treating chronic pain and diseases that have pain as a consequence of neuropathy. However, despite the growing body of evidence linking the efficacy of CBD on pain management in clinical and basic research, there is a lack of reviews focusing on chronic pain assessments, especially when considering pre-clinical studies, which assess chronic pain as a disease by itself or as a consequence of trauma or peripheral or central disease. Therefore, this review focused only on studies that fit our inclusion criteria: (1) used treatment with CBD extract; (2) used tests to assess mechanical or thermal nociception in at least one of the following most commonly used tests (von Frey, hot plate, acetone, Hargreaves, tail-flick, Randall & Selitto, and others); and (3) studies that assessed pain sensitivity in chronic pain induction models. The current literature points out that CBD is a well-tolerated and safe natural compound that exerts analgesic effects, decreasing hyperalgesia, and mechanical/thermal allodynia in several animal models of pain and patients. In addition, CBD presents several molecular and cellular mechanisms of action involved in its positive effects on chronic pain. In conclusion, using CBD seems to be a promising strategy to overcome the lack of efficacy of conventional treatment for chronic pain.

Review: Cannabinoids as Medicinals

PURPOSE OF REVIEW

There have been many debates, discussions, and published writings about the therapeutic value of cannabis plant and the hundreds of cannabinoids it contains. Many states and countries have attempted, are attempting, or have already passed bills to allow legal use of cannabinoids, especially cannabidiol (CBD), as medicines to treat a wide range of clinical conditions without having been approved by a regulatory body. Therefore, by using PubMed and Google Scholar databases, we have reviewed published papers during the past 30 years on cannabinoids as medicines and comment on whether there is sufficient clinical evidence from well-designed clinical studies and trials to support the use of CBD or any other cannabinoids as medicines.

RECENT FINDINGS

Current research shows that CBD and other cannabinoids currently are not ready for formal indications as medicines to treat a wide range of clinical conditions as promoted except for several exceptions including limited use of CBD for treating two rare forms of epilepsy in young children and CBD in combination with THC for treating multiple-sclerosis-associated spasticity.

SUMMARY

Research indicates that CBD and several other cannabinoids have potential to treat multiple clinical conditions, but more preclinical, and clinical studies and clinical trials, which follow regulatory guidelines, are needed to formally recommend CBD and other cannabinoids as medicines.

The Reversal of Empathy-Induced Hypernociception in Male Mice by Intra-Amygdala Administration of Midazolam and Cannabidiol Depends on 5-HT3 Receptors

Introduction: Empathy is a fundamental prosocial behavior. It has been defined as perception, awareness, and understanding of others' emotional states, including painful processes. Mice living in pairs with conspecific chronic suffering from constriction injury exhibit pain hypersensitivity mediated by the amygdaloid complex. Nevertheless, the underlying mechanisms in the amygdala responsible for this response remain to be determined. This study investigated if the anxiolytic benzodiazepine midazolam (MDZ) and cannabidiol (CBD), a phytocannabinoid with multiple molecular targets, would attenuate this behavioral change. We also investigated if serotonergic and γ-aminobutyric acid (GABA)ergic mechanisms in the amygdala are involved in this effect. Materials and Methods: Male Swiss mice were housed in pairs for 28 days. The pairs were divided into two groups on the 14th day: cagemate nerve constriction and cagemate sham. On the 24th day, cagemates underwent a stereotaxic surgery and, on the 28th day, were evaluated on the writhing test. Results: The results showed that living with chronic pain leads to hypernociception in the cagemate and increases the expression of 5-HT₃ receptor (5-HT₃R) and glutamic acid decarboxylase 67 within the amygdala. MDZ (3.0 and 30 nmol) and CBD (30 and 60 nmol) attenuated the hypernociceptive behavior. The 5-HT₃R antagonist ondansetron (0.3 nmol) prevented the antinociceptive effects of MDZ and CBD. Conclusion: These findings indicate that 5-HT₃R and GABAergic mechanisms within the amygdala are involved in the pain hypersensitivity induced by the empathy for pain model. They also suggest that MDZ and CBD could be a new potential therapy to alleviate emotional pain disorders.

Review: Cannabinoids as Medicinals

Purpose of review

There have been many debates, discussions, and published writings about the therapeutic value of cannabis plant and the hundreds of cannabinoids it contains. Many states and countries have attempted, are attempting, or have already passed bills to allow legal use of cannabinoids, especially cannabidiol (CBD), as medicines to treat a wide range of clinical conditions without having been approved by a regulatory body. Therefore, by using PubMed and Google Scholar databases, we have reviewed published papers during the past 30 years on cannabinoids as medicines and comment on whether there is sufficient clinical evidence from well-designed clinical studies and trials to support the use of CBD or any other cannabinoids as medicines.

Recent findings

Current research shows that CBD and other cannabinoids currently are not ready for formal indications as medicines to treat a wide range of clinical conditions as promoted except for several exceptions including limited use of CBD for treating two rare forms of epilepsy in young children and CBD in combination with THC for treating multiple-sclerosis-associated spasticity.

Summary

Research indicates that CBD and several other cannabinoids have potential to treat multiple clinical conditions, but more preclinical, and clinical studies and clinical trials, which follow regulatory guidelines, are needed to formally recommend CBD and other cannabinoids as medicines.

Cannabidiol enhances the antinociceptive effects of morphine and attenuates opioid-induced tolerance in the chronic constriction injury model

Neuropathic pain (NP) is a complex health problem that includes sensorial manifestations such as evoked and ongoing pain. Cannabidiol (CBD) has shown potential in the treatment of NP and the combination between opioids and cannabinoids has provided promising results on pain relief. Thus, our study aimed to investigate the effect of treatment combination between CBD and morphine on evoked and ongoing pain, and the effect of CBD on morphine-induced tolerance in the model of chronic constriction injury (CCI) of the sciatic nerve in rats. Mechanical thresholds (i.e., evoked pain) were evaluated before and 7 days after surgery. We also employed a 4-day conditioned place preference (CPP) protocol, to evaluate relief of ongoing pain (6-9 days after surgery). Treatment with morphine (2 and 4 mg/kg) or CBD (30 mg/kg) induced a significant antinociceptive effect on evoked pain. The combination of CBD (30 mg/kg) and morphine (1 mg/kg) produced an enhanced antinociceptive effect, when compared to morphine alone (1 mg/Kg). Treatment with morphine (1 and 2 mg/kg) or CBD (30 mg/kg) alone failed to induce significant scores in the CPP test. However, combined treatment of CBD (30 mg/kg) and morphine (1 mg/kg) provided significant positive scores, increased the number of entrances in the drug-paired chamber in the CPP test and did not alter locomotor activity in rats. Lastly, treatment with CBD partially attenuated morphine-induced tolerance. In summary, our results support the indication of CBD as an adjuvant to opioid therapy for the attenuation of NP and opioid-induced analgesic tolerance.

Anti-inflammatory potential of cannabidiol (CBD) on combination of caecal slurry, LPS, and E. coli-induced systemic inflammatory response syndrome (SIRS) in Sprague Dawley Rats

OBJECTIVE

The study objective was to evaluate the therapeutic effect of cannabidiol (CBD) on a combination of caecal slurry, lipopolysaccharide (LPS), and Escherichia coli (E. coli)-induced systemic inflammatory response syndrome (SIRS) in male Sprague Dawley rats.

METHODS

The therapeutic activity was monitored in behavioral tests and inflammatory biomarkers by the enzyme-linked immune sorbent assay (ELISA) method.

RESULTS

Behavioral tasks were significantly increased like a tail flick response by 73.84% (p ≤ 0.001), grip strength by 33.56% (p ≤ 0.028), locomotor activity by 20.71% (p = 0.034) in the CBD (60 mg/kg) group compared to disease control (DC) group. Levels of inflammatory serum biomarkers like interleukin-1β (IL-1β), matrix metallopeptidase-9 (MMP-9), IL-6, and tumor necrosis factor-alpha (TNF-α) were significantly decreased by 29.56 (p = 0.041), 71.20 (p ≤ 0.001), 35.05 (p ≤ 0.001), and 75.56% (p = 0.002), respectively, in the CBD-60 compared with DC. Inflammatory cytokines levels, viz. IL-1β, MMP-9, IL-6, and TNF-α, in the liver were significantly (p ≤ 0.001) decreased by 81.01, 40.41, 22.84, and 69.46%, respectively, in CBD-60 to DC. Similarly, levels of inflammatory cytokines such as IL-1β and MMP-9 in the kidney were significantly (p ≤ 0.001) decreased by 80.90 and 43.93%, respectively, in CBD-60 compared to DC.

CONCLUSION

Taken together, results suggest that CBD treatment significantly improved behavioral tasks and decreased the level of inflammatory cytokines under SIRS conditions that might provide an opportunity to manage acute and chronic inflammatory disorders.

Cannabidiol-based natural health products for companion animals: Recent advances in the management of anxiety, pain, and inflammation

Recent advances in cannabidiol (CBD) use in canines and felines for anxiety management, pain management, and anti-inflammatory effects were reviewed using a literature search conducted with the following keywords: CBD, anxiety, inflammation, pain, dogs, cats, and companion animals. For decades, research on CBD has been hindered due to the status of cannabis (C. sativa L.) as an illicit drug. Limited safety data show that CBD is well-tolerated in dogs, with insufficient information on the safety profile of CBD in cats. Upon oral supplementation of CBD, elevation in liver enzymes was observed for both dogs and cats, and pharmacokinetics of CBD are different in the two species. There is a significant gap in the literature on the therapeutic use of CBD in cats, with no feline data on anxiety, pain, and inflammation management. There is evidence that chronic osteoarthritic pain in dogs can be reduced by supplementation with CBD. Furthermore, experiments are required to better understand whether CBD has an influence on noise-induced fear and anxiolytic response. Preliminary evidence exists to support the analgesic properties of CBD in treating chronic canine osteoarthritis; however, there are inter- and intra-species differences in pharmacokinetics, tolerance, dosage, and safety of CBD. Therefore, to validate the anxiety management, pain management, and anti-inflammatory efficacy of CBD, it is essential to conduct systematic, randomized, and controlled trials. Further, the safety and efficacious dose of CBD in companion animals warrants investigation.

Cannabidiol effectively reverses mechanical and thermal allodynia, hyperalgesia, and anxious behaviors in a neuropathic pain model: Possible role of CB1 and TRPV1 receptors

The incidence of chronic pain is high in the general population and it is closely related to anxiety disorders, which promote negative effects on the quality of life. The cannabinoid system has essential participation in the pain sensitivity circuit. In this perspective, cannabidiol (CBD) is considered a promising strategy for treating neuropathic pain. Our study aimed to evaluate the effects of sub-chronic systemic treatment with CBD (0.3, 3, 10, or 30 mg/kg, i.p.) in male in rats submitted to chronic constriction injury of the sciatic nerve (CCI) or not (SHAM) and assessed in nociceptive tests (von Frey, acetone, and hot plate, three days CBD's treatment) and in the open field test (OFT, two days CBD's treatment). We performed a screening immunoreactivity of CB1 and TRPV1 receptors in cortical and limbic regions tissues, which were collected after 1.5 h of behavioral tests on the 24th experimental day. This study presents a dose-response curve to understand better the effects of low doses (3 mg/kg) on CBD's antiallodynic and anxiolytic effects. Also, low doses of CBD were able to (1) reverse mechanical and thermal allodynia (cold) and hyperalgesia, (2) reverse anxious behaviors (reduction of the % of grooming and freezing time, and increase of the % of center time in the OFT) induced by chronic pain. The peripheral neuropathy promoted the increase in the expression of CB1 and TRPV1 receptors in the anterior cingulate cortex (ACC), anterior insular cortex (AIC), basolateral amygdala (BLA), dorsal hippocampus (DH), and ventral hippocampus (VH). CBD potentiated this effect in the ACC, AIC, BLA, DH, and VH regions. These results provide substantial evidence of the role of the ACC-AIC-BLA corticolimbic circuit, and BLA-VH for pain regulation. These results can be clinically relevant since they contribute to the evidence of CBD's beneficial effects on treating chronic pain and associated comorbidities such as anxiety.

Cannabidiol has therapeutic potential for myofascial pain in female and male parkinsonian rats

The musculoskeletal orofacial pain is a complex symptom of Parkinson's disease (PD) resulting in stomatognathic system dysfunctions aggravated by the disease rigidity and postural instability. We tested the effect of cannabidiol (CBD), a non-psychotomimetic constituent of Cannabis sativa, in PD-related myofascial pain. Wistar adult female and male rats orofacial allodynic and hyperalgesic responses were tested by Von Frey and formalin tests, before and 21 days past 6-OHDA lesion. Algesic response was tested after masseter muscle injection of CBD (10, 50, 100 μg in 10 μL) or vehicle. Males compared to females in all estrous cycles' phases presented reduced orofacial allodynia and hyperalgesia. According to the estrous cycle's phases, females presented distinct orofacial nociceptive responses, being the estrus phase well-chosen for nociceptive analysis after 6-OHDA lesion (phase with fewer hormone alterations and adequate length). Dopaminergic neuron lesion decreased mechanical and inflammatory nociceptive thresholds in females and males in a higher proportion in females. CBD local treatment reduced the increased orofacial allodynia and hyperalgesia, in males and females. The female rats were more sensitive to CBD effect considering allodynia, responding to the lowest dose. Although females and males respond to the effect of three doses of CBD in the formalin test, males showed a superior reduction in the hyperalgesic response. These results indicate that hemiparkinsonian female in the estrus phase and male answer differently to the different doses of CBD therapy and nociceptive tests. CBD therapy is effective for parkinsonism-induced orofacial nociception.

Cannabinoids, the endocannabinoid system, and pain: a review of preclinical studies

ABSTRACT

This narrative review represents an output from the International Association for the Study of Pain's global task force on the use of cannabis, cannabinoids, and cannabis-based medicines for pain management, informed by our companion systematic review and meta-analysis of preclinical studies in this area. Our aims in this review are (1) to describe the value of studying cannabinoids and endogenous cannabinoid (endocannabinoid) system modulators in preclinical/animal models of pain; (2) to discuss both pain-related efficacy and additional pain-relevant effects (adverse and beneficial) of cannabinoids and endocannabinoid system modulators as they pertain to animal models of pathological or injury-related persistent pain; and (3) to identify important directions for future research. In service of these goals, this review (1) provides an overview of the endocannabinoid system and the pharmacology of cannabinoids and endocannabinoid system modulators, with specific relevance to animal models of pathological or injury-related persistent pain; (2) describes pharmacokinetics of cannabinoids in rodents and humans; and (3) highlights differences and discrepancies between preclinical and clinical studies in this area. Preclinical (rodent) models have advanced our understanding of the underlying sites and mechanisms of action of cannabinoids and the endocannabinoid system in suppressing nociceptive signaling and behaviors. We conclude that substantial evidence from animal models supports the contention that cannabinoids and endocannabinoid system modulators hold considerable promise for analgesic drug development, although the challenge of translating this knowledge into clinically useful medicines is not to be underestimated.

The role of the anterior pretectal nucleus in pain modulation: A comprehensive review

Descending pain modulation involves multiple encephalic sites and pathways that range from the cerebral cortex to the spinal cord. Behavioral studies conducted in the 1980s revealed that electrical stimulation of the pretectal area causes antinociception dissociation from aversive responses. Anatomical and physiological studies identified the anterior pretectal nucleus and its descending projections to several midbrain, pontine, and medullary structures. The anterior pretectal nucleus is morphologically divided into a dorsal part that contains a dense neuron population (pars compacta) and a ventral part that contains a dense fiber band network (pars reticulata). Connections of the two anterior pretectal nucleus parts are broad and include prominent projections to and from major encephalic systems associated with somatosensory processes. Since the first observation that acute or chronic noxious stimuli activate the anterior pretectal nucleus, it has been established that numerous mediators participate in this response through distinct pathways. Recent studies have confirmed that at least two pain inhibitory pathways are activated from the anterior pretectal nucleus. This review focuses on rodent anatomical, behavioral, molecular, and neurochemical data that have helped to identify mediators of the anterior pretectal nucleus and pathways related to its role in pain modulation.

Palmitoylethanolamide and hemp oil extract exert synergistic anti-nociceptive effects in mouse models of acute and chronic pain

The use of products derived from hemp - i.e., cannabis varieties with low Δ⁹-tetrahydrocannabinol (Δ⁹-THC) content - as self-medication for pain and other health conditions is gaining in popularity but preclinical and clinical evidence for their effectiveness remains very limited. In the present study, we assessed the efficacy of a full-spectrum hemp oil extract (HOE; 10, 50 and 100 mg-kg^-1; oral route), alone or in combination with the anti-inflammatory and analgesic agent palmitoylethanolamide (PEA; 10, 30, 100 and 300 mg-kg^-1; oral route), in the formalin and chronic constriction injury (CCI) tests. We found that HOE exerts modest antinociceptive effects when administered alone, whereas the combination of sub-effective oral doses of HOE and PEA produces a substantial greater-than-additive alleviation of pain-related behaviors. Transcription of interleukin (IL)-6 and IL-10 increased significantly in lumbar spinal cord tissue on day 7 after CCI surgery, an effect that was attenuated to the same extent by HOE alone or by the HOE/PEA combination. Pharmacokinetic experiments show that co-administration of HOE enhances and prolongs systemic exposure to PEA. Collectively, our studies lend support to possible beneficial effects of using HOE in combination with PEA to treat acute and chronic pain.

Cannabidiol for Pain Treatment: Focus on Pharmacology and Mechanism of Action

Cannabis has a long history of medical use. Although there are many cannabinoids present in cannabis, Δ9tetrahydrocannabinol (Δ9-THC) and cannabidiol (CBD) are the two components found in the highest concentrations. CBD itself does not produce typical behavioral cannabimimetic effects and was thought not to be responsible for psychotropic effects of cannabis. Numerous anecdotal findings testify to the therapeutic effects of CBD, which in some cases were further supported by research findings. However, data regarding CBD’s mechanism of action and therapeutic potential are abundant and omnifarious. Therefore, we review the basic research regarding molecular mechanism of CBD’s action with particular focus on its analgesic potential. Moreover, this article describes the detailed analgesic and anti-inflammatory effects of CBD in various models, including neuropathic pain, inflammatory pain, osteoarthritis and others. The dose and route of the administration-dependent effect of CBD, on the reduction in pain, hyperalgesia or allodynia, as well as the production of pro and anti-inflammatory cytokines, were described depending on the disease model. The clinical applications of CBD-containing drugs are also mentioned. The data presented herein unravel what is known about CBD’s pharmacodynamics and analgesic effects to provide the reader with current state-of-art knowledge regarding CBD’s action and future perspectives for research.

The effect of cannabidiol on sevoflurane minimum alveolar concentration reduction produced by morphine in rats

OBJECTIVE

To investigate the effect of cannabidiol (CBD) on sevoflurane minimum alveolar concentration (MAC_SEV) reduction produced by morphine in rats.

STUDY DESIGN

Randomized, blinded trial.

ANIMALS

A total of 75 male Wistar Han rats weighing 276 ± 23 g (mean and standard deviation), aged 3 months.

METHODS

Cannabidiol (CBD) was prepared in an ethanol-solutol-saline vehicle. Animals were randomly divided into 15 groups and given an intraperitoneal bolus of 1, 3, 5, 6.5, 7.5 or 10 mg kg^-1 of CBD alone (CBD1, CBD3, CBD5, CBD6.5, CBD7.5 and CBD10 respectively) or combined with 5 mg kg^-1 of morphine (MOR+CBD1, MOR+CBD3, MOR+CBD5, MOR+CBD6.5, MOR+CBD7.5 and MOR+CBD10). While three controls groups: MOR+saline, MOR+vehicle and vehicle were given an intraperitoneal bolus of morphine with saline, morphine with vehicle or vehicle alone respectively. The MAC_SEV was determined from alveolar gas samples at the time of tail clamp application. The MAC_SEV reduction was analyzed using a one-way ANOVA followed by Tukey's test. Additionally, Kruskal-Wallis test for non-normally-distributed data was performed. Data are presented as mean ± standard deviation. P < 0.05 RESULTS: The mean MAC_SEV was not reduced by the action of CBD administered alone, but the addition of morphine to the different doses of CBD significantly reduced the MAC_SEV. That reduction was greatest in the MOR+CBD1, MOR+CBD7.5 and MOR+CBD10 groups (29 ± 5%, 32 ± 5% and 30 ± 6% respectively), less in MOR+CBD3 and MOR+CBD6.5 groups (24 ± 3% and 26 ± 4% respectively) and least in MOR+CBD5 group (17 ± 2%). However, only the MOR+CBD5 group was statistically significantly different from MOR+CBD1, MOR+CBD7.5 and MOR+CBD10 groups.

CONCLUSIONS AND CLINICAL RELEVANCE

MAC_SEV in rat was unaltered by the action of CBD alone, the reduction in MAC_SEV produced by morphine was not enhanced by the addition of CBD at the doses studied.

Cannabidiol and Sports Performance: a Narrative Review of Relevant Evidence and Recommendations for Future Research

Cannabidiol (CBD) is a non-intoxicating cannabinoid derived from Cannabis sativa. CBD initially drew scientific interest due to its anticonvulsant properties but increasing evidence of other therapeutic effects has attracted the attention of additional clinical and non-clinical populations, including athletes. Unlike the intoxicating cannabinoid, Δ9-tetrahydrocannabinol (Δ9-THC), CBD is no longer prohibited by the World Anti-Doping Agency and appears to be safe and well-tolerated in humans. It has also become readily available in many countries with the introduction of over-the-counter "nutraceutical" products. The aim of this narrative review was to explore various physiological and psychological effects of CBD that may be relevant to the sport and/or exercise context and to identify key areas for future research. As direct studies of CBD and sports performance are is currently lacking, evidence for this narrative review was sourced from preclinical studies and a limited number of clinical trials in non-athlete populations. Preclinical studies have observed robust anti-inflammatory, neuroprotective and analgesic effects of CBD in animal models. Preliminary preclinical evidence also suggests that CBD may protect against gastrointestinal damage associated with inflammation and promote healing of traumatic skeletal injuries. However, further research is required to confirm these observations. Early stage clinical studies suggest that CBD may be anxiolytic in "stress-inducing" situations and in individuals with anxiety disorders. While some case reports indicate that CBD improves sleep, robust evidence is currently lacking. Cognitive function and thermoregulation appear to be unaffected by CBD while effects on food intake, metabolic function, cardiovascular function, and infection require further study. CBD may exert a number of physiological, biochemical, and psychological effects with the potential to benefit athletes. However, well controlled, studies in athlete populations are required before definitive conclusions can be reached regarding the utility of CBD in supporting athletic performance.

The Therapeutic Effectiveness of Full Spectrum Hemp Oil Using a Chronic Neuropathic Pain Model

BACKGROUND

Few models exist that can control for placebo and expectancy effects commonly observed in clinical trials measuring 'Cannabis' pharmacodynamics. We used the Foramen Rotundum Inflammatory Constriction Trigeminal Infraorbital Nerve injury (FRICT-ION) model to measure the effect of "full-spectrum" whole plant extracted hemp oil on chronic neuropathic pain sensitivity in mice.

METHODS

Male BALBc mice were submitted to the FRICT-ION chronic neuropathic pain model with oral insertion through an incision in the buccal/cheek crease of 3 mm of chromic gut suture (4-0). The suture, wedged along the V2 trigeminal nerve branch, creates a continuous irritation that develops into secondary mechanical hypersensitivity on the snout. Von Frey filament stimuli on the mouse whisker pad was used to assess the mechanical pain threshold from 0-6 h following dosing among animals (n = 6) exposed to 5 μL of whole plant extracted hemp oil combined with a peanut butter vehicle (0.138 mg/kg), the vehicle alone (n = 3) 7 weeks post-surgery, or a naïve control condition (n = 3).

RESULTS

Mechanical allodynia was alleviated within 1 h (d = 2.50, p < 0.001) with a peak reversal effect at 4 h (d = 7.21, p < 0.001) and remained significant throughout the 6 h observation window. There was no threshold change on contralateral whisker pad after hemp oil administration, demonstrating the localization of anesthetic response to affected areas.

CONCLUSION

Future research should focus on how whole plant extracted hemp oil affects multi-sensory and cognitive-attentional systems that process pain.

Terpenoids, Cannabimimetic Ligands, beyond the Cannabis Plant

Medicinal use of Cannabis sativa L. has an extensive history and it was essential in the discovery of phytocannabinoids, including the Cannabis major psychoactive compound-Δ9-tetrahydrocannabinol (Δ9-THC)-as well as the G-protein-coupled cannabinoid receptors (CBR), named cannabinoid receptor type-1 (CB1R) and cannabinoid receptor type-2 (CB2R), both part of the now known endocannabinoid system (ECS). Cannabinoids is a vast term that defines several compounds that have been characterized in three categories: (i) endogenous, (ii) synthetic, and (iii) phytocannabinoids, and are able to modulate the CBR and ECS. Particularly, phytocannabinoids are natural terpenoids or phenolic compounds derived from Cannabis sativa. However, these terpenoids and phenolic compounds can also be derived from other plants (non-cannabinoids) and still induce cannabinoid-like properties. Cannabimimetic ligands, beyond the Cannabis plant, can act as CBR agonists or antagonists, or ECS enzyme inhibitors, besides being able of playing a role in immune-mediated inflammatory and infectious diseases, neuroinflammatory, neurological, and neurodegenerative diseases, as well as in cancer, and autoimmunity by itself. In this review, we summarize and critically highlight past, present, and future progress on the understanding of the role of cannabinoid-like molecules, mainly terpenes, as prospective therapeutics for different pathological conditions.

Is cannabidiol the ideal drug to treat non-motor Parkinson's disease symptoms?

Parkinson's disease (PD) is a chronic neurodegenerative disorder characterized by motor symptoms such as bradykinesia, rest tremor, postural disturbances, and rigidity. PD is also characterized by non-motor symptoms such as sleep disturbances, cognitive deficits, and psychiatric disorders such as psychosis, depression, and anxiety. The pharmacological treatment for these symptoms is limited in efficacy and induce significant adverse reactions, highlighting the need for better treatment options. Cannabidiol (CBD) is a phytocannabinoid devoid of the euphoriant and cognitive effects of tetrahydrocannabinol, and preclinical and preliminary clinical studies suggest that this compound has therapeutic effect in non-motor symptoms of PD. In the present text, we review the clinical studies of cannabinoids in PD and the preclinical and clinical studies specifically on CBD. We found four randomized controlled trials (RCTs) involving the administration of agonists/antagonists of the cannabinoid 1 receptor, showing that these compounds were well tolerated, but only one study found positive results (reductions on levodopa-induced dyskinesia). We found seven preclinical models of PD using CBD, with six studies showing a neuroprotective effect of CBD. We found three trials involving CBD and PD: an open-label study, a case series, and an RCT. CBD was well tolerated, and all three studies reported significant therapeutic effects in non-motor symptoms (psychosis, rapid eye movement sleep behaviour disorder, daily activities, and stigma). However, sample sizes were small and CBD treatment was short (up to 6 weeks). Large-scale RCTs are needed to try to replicate these results and to assess the long-term safety of CBD.

Mechanisms of acute and chronic pain after surgery: update from findings in experimental animal models

PURPOSE OF REVIEW

Management of postoperative pain is still a major issue and relevant mechanisms need to be investigated. In preclinical research, substantial progress has been made, for example, by establishing specific rodent models of postoperative pain. By reviewing most recent preclinical studies in animals related to postoperative, incisional pain, we outline the currently available surgical-related pain models, discuss assessment methods for pain-relevant behavior and their shortcomings to reflect the clinical situation, delineate some novel clinical-relevant mechanisms for postoperative pain, and point toward future needs.

RECENT FINDINGS

Since the development of the first rodent model of postoperative, incisional pain almost 20 years ago, numerous variations and some procedure-specific models have been emerged including some conceivably relevant for investigating prolonged, chronic pain after surgery. Many mechanisms have been investigated by using these models; most recent studies focussed on endogenous descending inhibition and opioid-induced hyperalgesia. However, surgical models beyond the classical incision model have so far been used only in exceptional cases, and clinical relevant behavioral pain assays are still rarely utilized.

SUMMARY

Pathophysiological mechanisms of pain after surgery are increasingly discovered, but utilization of pain behavior assays are only sparsely able to reflect clinical-relevant aspects of acute and chronic postoperative pain in patients.

Cannabidiol presents an inverted U-shaped dose-response curve in a simulated public speaking test

Objective:

Cannabidiol (CBD), one of the non-psychotomimetic compounds of Cannabis sativa, causes anxiolytic-like effects in animals, with typical bell-shaped dose-response curves. No study, however, has investigated whether increasing doses of this drug would also cause similar curves in humans. The objective of this study was to compare the acute effects of different doses of CBD and placebo in healthy volunteers performing a simulated public speaking test (SPST), a well-tested anxiety-inducing method.

Method:

A total of 57 healthy male subjects were allocated to receive oral CBD at doses of 150 mg (n=15), 300 mg (n=15), 600 mg (n=12) or placebo (n=15) in a double-blind procedure. During the SPST, subjective ratings on the Visual Analogue Mood Scale (VAMS) and physiological measures (systolic and diastolic blood pressure, heart rate) were obtained at six different time points.

Results:

Compared to placebo, pretreatment with 300 mg of CBD significantly reduced anxiety during the speech. No significant differences in VAMS scores were observed between groups receiving CBD 150 mg, 600 mg and placebo.

Conclusion:

Our findings confirm the anxiolytic-like properties of CBD and are consonant with results of animal studies describing bell-shaped dose-response curves. Optimal therapeutic doses of CBD should be rigorously determined so that research findings can be adequately translated into clinical practice.

Cannabinoid-Based Therapies and Brain Development: Potential Harmful Effect of Early Modulation of the Endocannabinoid System

The endocannabinoid retrograde signaling pathway is widely expressed in the central nervous system, where it plays major roles in regulating synaptic plasticity (excitatory and inhibitory) through long-term potentiation and long-term depression. The endocannabinoid system (ECS) components-cannabinoid receptors, endocannabinoids and synthesis/degradation enzymes-are expressed and are functional from early developmental stages and throughout adolescent cortical development, regulating progenitor cell fate, neural differentiation, migration and survival. This may potentially confer increased vulnerability to adverse outcomes from early cannabinoid exposure. Cannabidiol (CBD) is one of the most studied exogenous cannabinoids, and CBD-enriched Cannabis extracts have been widely (and successfully) used as adjuvants to treat children with refractory epilepsy, and there is even a Food and Drug Administration (FDA)-approved drug with purified CBD derived from Cannabis. However, there is insufficient information on possible long-term changes in the central nervous system caused by cannabinoid treatments during early childhood. Like the majority of cannabinoids, CBD is able to exert its effects directly and indirectly through the ECS, which can perturb the regulatory processes mediated by this system. In addition, CBD has a large number of non-endocannabinoid targets, which can explain CBD's effects. Here, we review the current knowledge about CBD-based therapies-pure and CBD-enriched Cannabis extracts-in studies with pediatric patients, their side effects, and their mechanisms of action regarding the central nervous system and neurodevelopment aspects. Since Cannabis extracts contain Δ⁹-tetrahydrocannabinol (Δ⁹-THC), we consider that pure CBD is possibly safer for young patients. Nevertheless, CBD, as well as other natural and/or synthetic cannabinoids, should be studied in more detail as a therapeutic alternative to CBD-enriched Cannabis extracts for young patients.