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

Cannabidiol and pain

Chronic pain presents significant personal, psychological, and socioeconomic hurdles, impacting over 30% of adults worldwide and substantially contributing to disability. Unfortunately, current pharmacotherapy often proves inadequate, leaving fewer than 70% of patients with relief. This shortfall has sparked a drive to seek alternative treatments offering superior safety and efficacy profiles. Cannabinoid-based pharmaceuticals, notably cannabidiol (CBD), hold promise in pain management, driven by their natural origins, versatility, and reduced risk of addiction. As we navigate the opioid crisis, ongoing research plunges into CBD's therapeutic potential, buoyed by animal studies revealing its pain-relieving prowess through various system tweaks. However, the efficacy of cannabis in chronic pain management remains a contentious and stigmatized issue. The International Association for the Study of Pain (IASP) presently refrains from endorsing cannabinoid use for pain relief. Nevertheless, evidence indicates their potential in alleviating cancer-related, neuropathic, arthritis, and musculoskeletal pain, necessitating further investigation. Crucially, our comprehension of CBD's role in pain management is a journey still unfolding, with animal studies illustrating its analgesic effects through interactions with the endocannabinoid, inflammatory, and nociceptive systems. As the plot thickens, it's clear: the saga of chronic pain and CBD's potential offers a compelling narrative ripe for further exploration and understanding.

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.

Promising immunomodulators for management of substance and alcohol use disorders

INTRODUCTION

The neuroimmune system has emerged as a novel target for the treatment of substance use disorders (SUDs), with immunomodulation producing encouraging therapeutic benefits in both preclinical and clinical settings.

AREAS COVERED

In this review, we describe the mechanism of action and immune response to methamphetamine, opioids, cocaine, and alcohol. We then discuss off-label use of immunomodulators as adjunctive therapeutics in the treatment of neuropsychiatric disorders, demonstrating their potential efficacy in affective and behavioral disorders. We then discuss in detail the mechanism of action and recent findings regarding the use of ibudilast, minocycline, probenecid, dexmedetomidine, pioglitazone, and cannabidiol to treat (SUDs). These immunomodulators are currently being investigated in clinical trials described herein, specifically for their potential to decrease substance use, withdrawal severity, central and peripheral inflammation, comorbid neuropsychiatric disorder symptomology, as well as their ability to improve cognitive outcomes.

EXPERT OPINION

We argue that although mixed, findings from recent preclinical and clinical studies underscore the potential benefit of immunomodulation in the treatment of the behavioral, cognitive, and inflammatory processes that underlie compulsive substance use.

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.

Endogenous opiates and behavior: 2022

This paper is the forty-fifth consecutive installment of the annual anthological review of research concerning the endogenous opioid system, summarizing articles published during 2022 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides and receptors as well as effects of opioid/opiate agonists and antagonists. The review is subdivided into the following specific topics: molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors (1), the roles of these opioid peptides and receptors in pain and analgesia in animals (2) and humans (3), opioid-sensitive and opioid-insensitive effects of nonopioid analgesics (4), opioid peptide and receptor involvement in tolerance and dependence (5), stress and social status (6), learning and memory (7), eating and drinking (8), drug abuse and alcohol (9), sexual activity and hormones, pregnancy, development and endocrinology (10), mental illness and mood (11), seizures and neurologic disorders (12), electrical-related activity and neurophysiology (13), general activity and locomotion (14), gastrointestinal, renal and hepatic functions (15), cardiovascular responses (16), respiration and thermoregulation (17), and immunological responses (18).

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.

Research trends and hotspots of neuropathic pain in neurodegenerative diseases: a bibliometric analysis

Background

Neuropathic pain is caused by a neurological injury or disease and can have a significant impact on people's daily lives. Studies have shown that neuropathic pain is commonly associated with neurodegenerative diseases. In recent years, there has been a lot of literature on the relationship between neuropathic pain and neurodegenerative diseases. However, bibliometrics is rarely used in analyzing the general aspects of studies on neuropathic pain in neurodegenerative diseases.

Methods

The bibliometric analysis software CiteSpace and VOSviewer were used to analyze the knowledge graph of 387 studies in the Science Citation Index Expanded of the Web of Science Core Collection Database.

Results

We obtained 2,036 documents through the search, leaving 387 documents after culling. 387 documents were used for the data analysis. The data analysis showed that 330 papers related to neuropathic pain in neurodegenerative diseases were published from 2007-2022, accounting for 85.27% of all published literature. In terms of contributions to the scientific study of neuropathic pain, the United States is in the top tier, with the highest number of publications, citations, and H-indexes.

Conclusion

The findings in our study may provide researchers with useful information about research trends, frontiers, and cooperative institutions. Multiple sclerosis, Parkinson's disease, and Alzheimer's disease are the three most studied neurodegenerative diseases. Among the pathological basis of neurodegenerative diseases, microglia-regulated neuroinflammation is a hot research topic. Deep brain stimulation and gamma knife radiosurgery are two popular treatments.

The therapeutic potential of purified cannabidiol

The use of cannabidiol (CBD) for therapeutic purposes is receiving considerable attention, with speculation that CBD can be useful in a wide range of conditions. Only one product, a purified form of plant-derived CBD in solution (Epidiolex), is approved for the treatment of seizures in patients with Lennox-Gastaut syndrome, Dravet syndrome, or tuberous sclerosis complex. Appraisal of the therapeutic evidence base for CBD is complicated by the fact that CBD products sometimes have additional phytochemicals (like tetrahydrocannabinol (THC)) present, which can make the identification of the active pharmaceutical ingredient (API) in positive studies difficult. The aim of the present review is to critically review clinical studies using purified CBD products only, in order to establish the upcoming indications for which purified CBD might be beneficial. The areas in which there is the most clinical evidence to support the use of CBD are in the treatment of anxiety (positive data in 7 uncontrolled studies and 17 randomised controlled trials (RCTs)), psychosis and schizophrenia (positive data in 1 uncontrolled study and 8 RCTs), PTSD (positive data in 2 uncontrolled studies and 4 RCTs) and substance abuse (positive data in 2 uncontrolled studies and 3 RCTs). Seven uncontrolled studies support the use of CBD to improve sleep quality, but this has only been verified in one small RCT. Limited evidence supports the use of CBD for the treatment of Parkinson's (3 positive uncontrolled studies and 2 positive RCTs), autism (3 positive RCTs), smoking cessation (2 positive RCTs), graft-versus-host disease and intestinal permeability (1 positive RCT each). Current RCT evidence does not support the use of purified oral CBD in pain (at least as an acute analgesic) or for the treatment of COVID symptoms, cancer, Huntington's or type 2 diabetes. In conclusion, published clinical evidence does support the use of purified CBD in multiple indications beyond epilepsy. However, the evidence base is limited by the number of trials only investigating the acute effects of CBD, testing CBD in healthy volunteers, or in very small patient numbers. Large confirmatory phase 3 trials are required in all indications.

Ferulic acid-loaded nanostructure prevents morphine reinstatement: the involvement of dopamine system, NRF2, and ΔFosB in the striatum brain area of rats

Morphine is among the most powerful analgesics and pain-relieving agents. However, its addictive properties limit their medical use because patients may be susceptible to abuse and reinstatement. Morphine addiction occurs because of dopamine release in the mesolimbic brain area, implying in an increase in oxidative stress. Ferulic acid (FA), a phenolic phytochemical found in a variety of foods, has been reported to exert antioxidant and neuroprotective effects; however, its low bioavailability makes its nano-encapsulated form a promising alternative. This study aimed to evaluate the protective effects of a novel nanosystem with FA on morphine reinstatement and the consequent molecular neuroadaptations and oxidative status in the mesolimbic region. Rats previously exposed to morphine in conditioned place preference (CPP) paradigm were treated with ferulic acid-loaded nanocapsules (FA-Nc) or nonencapsulated FA during morphine-preference extinction. Following the treatments, animals were re-exposed to morphine to induce the reinstatement. While morphine-preference extinction was comparable among all experimental groups, FA-Nc treatment prevented morphine reinstatement. In the dorsal striatum, while morphine exposure increased lipid peroxidation (LP) and reactive species (RS), FA-Nc decreased LP and FA decreased RS levels. Morphine exposure increased the dopaminergic markers (D1R, D3R, DAT) and ΔFosB immunoreactivity in the ventral striatum; however, FA-Nc treatment decreased D1R, D3R, and ΔFosB and increased D2R, DAT, and NRF2. In conclusion, FA-Nc treatment prevented the morphine reinstatement, promoted antioxidant activity, and modified the dopaminergic neurotransmission, NRF2, and ΔFosB, what may indicate a neuroprotective and antioxidant role of this nanoformulation.

Differential regulation of Cav 3.2 and Cav 2.2 calcium channels by CB1 receptors and cannabidiol

BACKGROUND AND PURPOSE

Cannabinoids are a promising therapeutic avenue for chronic pain. However, clinical trials often fail to report analgesic efficacy of cannabinoids. Inhibition of voltage gate calcium (Ca_v ) channels is one mechanism through which cannabinoids may produce analgesia. We hypothesized that cannabinoids and cannabinoid receptor agonists target different types of Ca_v channels through distinct mechanisms.

EXPERIMENTAL APPROACH

Electrophysiological recordings from tsA-201 cells expressing either Ca_v 3.2 or Ca_v 2.2 were used to assess inhibition by HU-210 or cannabidiol (CBD) in the absence and presence of the CB₁ receptor. Homology modelling assessed potential interaction sites for CBD in both Ca_v 2.2 and Ca_v 3.2. Analgesic effects of CBD were assessed in mouse models of inflammatory and neuropathic pain.

KEY RESULTS

HU-210 (1 μM) inhibited Ca_v 2.2 function in the presence of CB₁ receptor but had no effect on Ca_v 3.2 regardless of co-expression of CB₁ receptor. By contrast, CBD (3 μM) produced no inhibition of Ca_v 2.2 and instead inhibited Ca_v 3.2 independently of CB₁ receptors. Homology modelling supported these findings, indicating that CBD binds to and occludes the pore of Ca_v 3.2, but not Ca_v 2.2. Intrathecal CBD alleviated thermal and mechanical hypersensitivity in both male and female mice, and this effect was absent in Ca_v 3.2 null mice.

CONCLUSION AND IMPLICATIONS

Our findings reveal differential modulation of Ca_v 2.2 and Ca_v 3.2 channels by CB₁ receptors and CBD. This advances our understanding of how different cannabinoids produce analgesia through action at different voltage-gated calcium channels and could influence the development of novel cannabinoid-based therapeutics for treatment of chronic pain.