Category Archives: Pain

Involvement of cannabinoid receptors in peripheral and spinal morphine analgesia.

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“The interactions between the cannabinoid and opioid systems for pain modulation are reciprocal. However, the role and the importance of the cannabinoid system in the antinociceptive effects of opioids remain uncertain. We studied these interactions with the goal of highlighting the involvement of the cannabinoid system in morphine-induced analgesia.

In both phases of the formalin test, intra paw and intrathecal morphine produced similar antinociceptive effects in C57BL/6, cannabinoid type 1 and type 2 receptor wildtype (respectively cnr1WT and cnr2WT) mice. In cnr1 and cnr2 knockout (KO) mice, at the dose used the antinociceptive effect of intra paw morphine in the inflammatory phase of the formalin test was decreased by 87% and 76%, respectively. Similarly, the antinociceptive effect of 0.1 μg spinal morphine in the inflammatory phase was abolished in cnr1KO mice and decreased by 90% in cnr2KO mice. Interestingly, the antinociceptive effect of morphine in the acute phase of the formalin test was only reduced in cnr1KO mice. Notably, systemic morphine administration produced similar analgesia in all genotypes, in both the formalin and the hot water immersion tail flick tests.

Because the pattern of expression of the mu opioid receptor (MOP), its binding properties and its G protein coupling remained unchanged across genotypes, it is unlikely that the loss of morphine analgesia in the cnr1KO and cnr2KO mice is the consequence of MOP malfunction or downregulation due to the absence of its heterodimerization with either the CB1 or the CB2 receptors, at least at the level of the spinal cord.”

http://www.ncbi.nlm.nih.gov/pubmed/24365460

The agonist binding mechanism of human CB2 receptor studied by molecular dynamics simulation, free energy calculation and 3D-QSAR studies.

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“CB2-selective agonists have drawn attention in drug discovery, since CB2 becomes a promising target for the treatment of neuropathic pain without psychoactive or other CNS-related side effects…

A combinational exploration of both CoMFA steric and potential contour maps for CB2 affinities and the MD studied interaction modes sheds light on the structural requirements for CB2 agonists and serves as a basis for the design of novel CB2 agonists.”

http://www.ncbi.nlm.nih.gov/pubmed/24358778

Cannabinoid CB2 Receptors Regulate Central Sensitization and Pain Responses Associated with Osteoarthritis of the Knee Joint.

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“Osteoarthritis (OA) of the joint is a prevalent disease accompanied by chronic, debilitating pain. Recent clinical evidence has demonstrated that central sensitization contributes to OA pain. An improved understanding of how OA joint pathology impacts upon the central processing of pain is crucial for the identification of novel analgesic targets/new therapeutic strategies.

Inhibitory cannabinoid 2 (CB2) receptors attenuate peripheral immune cell function and modulate central neuro-immune responses in models of neurodegeneration…

These findings suggest that targeting CB2 receptors may have therapeutic potential for treating OA pain.”

http://www.ncbi.nlm.nih.gov/pubmed/24282543

The endocannabinoid system, cannabinoids, and pain.

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“The endocannabinoid system is involved in a host of homeostatic and physiologic functions, including modulation of pain and inflammation… Exogenous plant-based cannabinoids (phytocannabinoids) and chemically related compounds, like the terpenes, commonly found in many foods, have been found to exert significant analgesic effects in various chronic pain conditions.

Currently, the use of Δ9-tetrahydrocannabinol is limited by its psychoactive effects and predominant delivery route (smoking), as well as regulatory or legal constraints.

 However, other phytocannabinoids in combination, especially cannabidiol and β-caryophyllene, delivered by the oral route appear to be promising candidates for the treatment of chronic pain due to their high safety and low adverse effects profiles.

This review will provide the reader with the foundational basic and clinical science linking the endocannabinoid system and the phytocannabinoids with their potentially therapeutic role in the management of chronic pain.”

http://www.ncbi.nlm.nih.gov/pubmed/24228165

The endocannabinoid system mediates aerobic exercise-induced antinociception in rats.

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“These results indicate that exercise could activate the endocannabinoid system, producing antinociception.

Supporting this hypothesis, liquid-chromatography/mass-spectrometry measurements demonstrated that plasma levels of endocannabinoids (anandamide and 2-arachidonoylglycerol) and of anandamide-related mediators (palmitoylethanolamide and oleoylethanolamide) were increased after AE.

Therefore, these results suggest that the endocannabinoid system mediates aerobic exercise-induced antinociception at peripheral and central levels.”

http://www.ncbi.nlm.nih.gov/pubmed/24148812

Endocannabinoid system and pain: an introduction.

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“The endocannabinoid (EC) system consists of two main receptors: cannabinoid type 1 receptor cannabinoid receptors are found in both the central nervous system (CNS) and periphery, whereas the cannabinoid type 2 receptor cannabinoid receptor is found principally in the immune system and to a lesser extent in the CNS.

 The EC family consists of two classes of well characterised ligands; the N-acyl ethanolamines, such as N-arachidonoyl ethanolamide or anandamide (AEA), and the monoacylglycerols, such as 2-arachidonoyl glycerol. The various synthetic and catabolic pathways for these enzymes have been (with the exception of AEA synthesis) elucidated.

 To date, much work has examined the role of EC in nociceptive processing and the potential of targeting the EC system to produce analgesia.

Cannabinoid receptors and ligands are found at almost every level of the pain pathway from peripheral sites, such as peripheral nerves and immune cells, to central integration sites such as the spinal cord, and higher brain regions such as the periaqueductal grey and the rostral ventrolateral medulla associated with descending control of pain. EC have been shown to induce analgesia in preclinical models of acute nociception and chronic pain states.

 The purpose of this review is to critically evaluate the evidence for the role of EC in the pain pathway and the therapeutic potential of EC to produce analgesia. We also review the present clinical work conducted with EC, and examine whether targeting the EC system might offer a novel target for analgesics, and also potentially disease-modifying interventions for pathophysiological pain states.”

http://www.ncbi.nlm.nih.gov/pubmed/24148358

The oral administration of trans-caryophyllene attenuates acute and chronic pain in mice.

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“Trans-caryophyllene is a sesquiterpene present in many medicinal plants’ essential oils, such as Ocimum gratissimum and Cannabis sativa. In this study, we evaluated the antinociceptive activity of trans-caryophyllene in murine models of acute and chronic pain and the involvement of trans-caryophyllene in the opioid and endocannabinoid systems…

 These results demonstrate that trans-caryophyllene reduced both acute and chronic pain in mice, which may be mediated through the opioid and endocannabinoid systems.”

http://www.ncbi.nlm.nih.gov/pubmed/24055516

Therapeutic potential of cannabinoid medicines.

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Drug Testing and Analysis

“Cannabis was extensively used as a medicine throughout the developed world in the nineteenth century but went into decline early in the twentieth century ahead of its emergence as the most widely used illicit recreational drug later that century. Recent advances in cannabinoid pharmacology alongside the discovery of the endocannabinoid system (ECS) have re-ignited interest in cannabis-based medicines.

The ECS has emerged as an important physiological system and plausible target for new medicines. Its receptors and endogenous ligands play a vital modulatory role in diverse functions including immune response, food intake, cognition, emotion, perception, behavioural reinforcement, motor co-ordination, body temperature, wake/sleep cycle, bone formation and resorption, and various aspects of hormonal control. In disease it may act as part of the physiological response or as a component of the underlying pathology.

In the forefront of clinical research are the cannabinoids delta-9-tetrahydrocannabinol and cannabidiol, and their contrasting pharmacology will be briefly outlined. The therapeutic potential and possible risks of drugs that inhibit the ECS will also be considered. This paper will then go on to review clinical research exploring the potential of cannabinoid medicines in the following indications: symptomatic relief in multiple sclerosis, chronic neuropathic pain, intractable nausea and vomiting, loss of appetite and weight in the context of cancer or AIDS, psychosis, epilepsy, addiction, and metabolic disorders.”

http://www.ncbi.nlm.nih.gov/pubmed/24006213

http://onlinelibrary.wiley.com/doi/10.1002/dta.1529/abstract

Texas A&M Pharmacy Researcher Fights Cancer, Pain With New Cannabinoid Receptor Drug

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DrDaiLu

“Dr. Lu has been working to find new types of chemotherapeutic drugs that both kill pancreatic cancer and suppress the cancer pain at the same time by targeting a special G-protein coupled receptor that belongs to the biological system responsible for the effects of Tetrahydrocannabinol (THC), a compound derived from some varieties of cannabis (hemp) or made synthetically, that is the primary psychoactive agent in marijuana and hashish.

 Dr. Lu says pancreatic cancer cells have more type 2 cannabinoid receptors than do healthy cells.

 Consequently, drug molecules that selectively activate this receptor can induce cancer cell death without affecting normal pancreatic cells, noting that when given to mice with pancreatic tumors, the molecule prevented tumor growth and suppressed the spread of cancer to healthy organs.

 Meanwhile, this class of compounds also generates painkillers comparable to morphine’s pain killing effect…”

More: http://www.bionews-tx.com/news/2013/08/20/texas-am-pharmacy-researcher-fights-cancer-pain-with-new-cannabinoid-receptor-drug/

The Major Brain Endocannabinoid 2-AG Controls Neuropathic Pain and Mechanical Hyperalgesia in Patients with Neuromyelitis Optica.

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“Recurrent myelitis is one of the predominant characteristics in patients with neuromyelitis optica (NMO). While paresis, visual loss, sensory deficits, and bladder dysfunction are well known symptoms in NMO patients, pain has been recognized only recently as another key symptom of the disease. Although spinal cord inflammation is a defining aspect of neuromyelitis, there is an almost complete lack of data on altered somatosensory function, including pain. Therefore, eleven consecutive patients with NMO were investigated regarding the presence and clinical characteristics of pain. All patients were examined clinically as well as by Quantitative Sensory Testing (QST) following the protocol of the German Research Network on Neuropathic Pain (DFNS). Additionally, plasma endocannabinoid levels and signs of chronic stress and depression were determined. Almost all patients (10/11) suffered from NMO-associated neuropathic pain for the last three months, and 8 out of 11 patients indicated relevant pain at the time of examination. Symptoms of neuropathic pain were reported in the vast majority of patients with NMO. Psychological testing revealed signs of marked depression. Compared to age and gender-matched healthy controls, QST revealed pronounced mechanical and thermal sensory loss, strongly correlated to ongoing pain suggesting the presence of deafferentation-induced neuropathic pain. Thermal hyperalgesia correlated to MRI-verified signs of spinal cord lesion. Heat hyperalgesia was highly correlated to the time since last relapse of NMO. Patients with NMO exhibited significant mechanical and thermal dysesthesia, namely dynamic mechanical allodynia and paradoxical heat sensation. Moreover, they presented frequently with either abnormal mechanical hypoalgesia or hyperalgesia, which depended significantly on plasma levels of the endogenous cannabinoid 2-arachidonoylglycerole (2-AG). These data emphasize the high prevalence of neuropathic pain and hyperalgesia in patients with NMO. The degree of mechanical hyperalgesia reflecting central sensitization of nociceptive pathways seems to be controlled by the major brain endocannabinoid 2-AG.”

http://www.ncbi.nlm.nih.gov/pubmed/23951176