Changes in Monoaminergic Neurotransmission in an Animal Model of Osteoarthritis: The Role of Endocannabinoid Signaling.

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“Chronic pain is a main symptom of osteoarthritis (OA). Moreover, a high percentage of OA patients suffer from mental health problems.

The endocannabinoid (EC) system has attracted attention as an emerging drug target for pain treatment together with its activity on the mesolimbic reward system.

Understanding the circuits that govern the reward of pain relief is crucial for the search for effective analgesics. Therefore, we investigated the role of the EC system on dopamine (DA) and noradrenaline (NA) in an animal model of OA-related chronic pain.

Our results demonstrated that chronic pain in OA rats was reflected by the inhibition of mesolimbic and mesocortical dopaminergic transmission, and may indicate the pro-pain role of NA in the FCx.

The data provide understanding about changes in neurotransmission in chronic pain states and may explain the clinical improvement in perceived life quality following cannabinoid treatment.

Additional mechanistic studies in preclinical models examining the intersection between chronic pain and reward circuits may offer new approaches for improving pain therapy.”

https://www.ncbi.nlm.nih.gov/pubmed/30618615

https://www.frontiersin.org/articles/10.3389/fnmol.2018.00466/full

Pharmacokinetics, Safety, and Clinical Efficacy of Cannabidiol Treatment in Osteoarthritic Dogs.

“The objectives of this study were to determine basic oral pharmacokinetics, and assess safety and analgesic efficacy of a cannabidiol (CBD) based oil in dogs with osteoarthritis (OA). Results: Pharmacokinetics revealed an elimination half-life of 4.2 h at both doses and no observable side effects. Clinically, canine brief pain inventory and Hudson activity scores showed a significant decrease in pain and increase in activity (p < 0.01) with CBD oil. Veterinary assessment showed decreased pain during CBD treatment (p < 0.02). No side effects were reported by owners, however, serum chemistry showed an increase in alkaline phosphatase during CBD treatment (p < 0.01). Clinical significance: This pharmacokinetic and clinical study suggests that 2 mg/kg of CBD twice daily can help increase comfort and activity in dogs with OA.” https://www.ncbi.nlm.nih.gov/pubmed/30083539 https://www.frontiersin.org/articles/10.3389/fvets.2018.00165/full]]>

Endogenous systems involved in exercise-induced analgesia.

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“Exercise-induced analgesia is a phenomenon discussed worldwide. This effect began to be investigated in the early 1970s in healthy individuals and rodents during and after an acute or chronic session of running or swimming. Thereafter, studies found this effect was also induced by resistance exercises. Over the years, many studies have demonstrated the importance of exercise-induced analgesia in relieving pain caused by different conditions, such as fibromyalgia, low back pain, neuropathy, and osteoarthritis. This review aims to provide the reader with an in-depth description of the main endogenous systems, substances, neurotransmitters, receptors and enzymes that are thought to be involved in the analgesic effect induced by exercise. Many hypotheses have been proposed to elucidate the mechanisms responsible for exercise-induced analgesia. One of the most accepted hypotheses has been the activation of several endogenous systems described as analgesics. Studies have demonstrated that during and after exercise different endogenous systems are activated, which release substances or neurotransmitters, such as opioids, nitric oxide, serotonin, catecholamines and endocannabinoids, that may modulate the pain perception.”  https://www.ncbi.nlm.nih.gov/pubmed/29769416 http://www.jpp.krakow.pl/journal/archive/02_18/pdf/jpp.2018.1.01.pdf

“Exercise activates the endocannabinoid system.”  https://www.ncbi.nlm.nih.gov/pubmed/14625449

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