Mu-opioid receptors in nociceptive afferents produce a sustained suppression of hyperalgesia in chronic pain

The latent sensitization model of chronic pain reveals that recovery from some types of long-term hyperalgesia is an altered state in which nociceptive sensitization persists but is suppressed by the ongoing activity of analgesic receptors such as μ-opioid receptors (MORs). To determine whether these MORs are the ones present in nociceptive afferents, we bred mice expressing Cre-recombinase under the Nav1.8 channel promoter (Nav1.8cre) with MOR-floxed mice (flMOR). These Nav1.8cre/flMOR mice had reduced MOR expression in primary afferents, as revealed by quantitative PCR, in situ hybridization, and immunofluorescence colocalization with the neuropeptide calcitonin gene-related peptide. We then studied the recovery from chronic pain of these mice and their flMOR littermates. When Nav1.8cre/flMOR mice were injected in the paw with complete Freund adjuvant they developed mechanical hyperalgesia that persisted for more than 2 months, whereas the responses of flMOR mice returned to baseline after 3 weeks. We then used the inverse agonist naltrexone to assess ongoing MOR activity. Naltrexone produced a robust reinstatement of hyperalgesia in control flMOR mice, but produced no effect in the Nav1.8/flMOR males and a weak reinstatement of hyperalgesia in Nav1.8/flMOR females. Naltrexone also reinstated swelling of the hind paw in flMOR mice and female Nav1.8cre/flMOR mice, but not male Nav1.8cre/flMOR mice. The MOR agonist DAMGO inhibited substance P release in flMOR mice but not ...
Source: Pain - Category: Anesthesiology Tags: Research Paper Source Type: research

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CONCLUSION: The etiology of chronic groin pain post hernia repair is related in part to nerve injury. This is supported by the high frequency of sensory symptoms and numbness in these patients. However other factors including the role of tissue injury and inflammatory postoperative changes need to be considered. KEY WORDS: Chronic postoperative pain, Inguinal hernia repair, Open surgery, Laparoscopic surgery. PMID: 31719216 [PubMed - as supplied by publisher]
Source: Annali Italiani di Chirurgia - Category: Surgery Tags: Ann Ital Chir Source Type: research
Abstract The Editor-in-Chief has retracted this article [1] because an investigation by Keio University has concluded that there are inaccuracies in the data reported. PMID: 31730223 [PubMed - in process]
Source: Aging Clinical and Experimental Research - Category: Geriatrics Authors: Tags: Aging Clin Exp Res Source Type: research
The opioid epidemic is a significant public health concern linked to chronic pain. Despite efforts to change opioid prescribing practices for chronic pain, opioid-involved overdoses remain at an all-time high. Research focused on identifying individual dif...
Source: SafetyLit - Category: International Medicine & Public Health Tags: Alcohol and Other Drugs Source Type: news
Publication date: Available online 16 November 2019Source: Orthopaedics &Traumatology: Surgery &ResearchAuthor(s): Christophe Mathoulin, Mathilde GrasAbstractScapholunate ligament tear is most frequently encountered in the aftermath of trauma in supination and extension of the wrist. It generates chronic instability, leading to osteoarthritis. It may be associated with fracture of the distal epiphysis of the radius or of the scaphoid. These lesions are often difficult to diagnose, especially in early stages. Treatment of chronic scapholunate ligament lesions before onset of osteoarthritis is a challenge for the sur...
Source: Orthopaedics and Traumatology: Surgery and Research - Category: Orthopaedics Source Type: research
ConclusionsPatients with lower educational level showed a three-time higher association to develop CPSP. Considering SHD could be of relevance when elaborating new interventions or health strategies and more specialized counseling for patients with persistent pain after TKA.
Source: International Orthopaedics - Category: Orthopaedics Source Type: research
Publication date: Available online 14 November 2019Source: Life SciencesAuthor(s): Wanli Ji, Kun Liang, Rui An, Xinhong WangAbstractAimsCurrently, chronic gastritis is a high incidence of digestive diseases, along with loss of appetite, abdominal pain and diarrhea. Baicalin belongs to the major bioactive flavonoids compounds from Scutellariae Radix, it exhibited anti-inflammatory and anti-bacteria activities. Nonetheless, the protective effects of baicalin on ethanol-induced gastritis have not been completely clarified. Our study was designed to evaluate the protective activity of baicalin on ethanol-induced chronic gastri...
Source: Life Sciences - Category: Biology Source Type: research
Publication date: Available online 15 November 2019Source: Journal of Pediatric Surgery Case ReportsAuthor(s): I. Stoica, A. Muntean, M.B. McDermott, F.M.J. QuinnAbstractXanthogranulomatous pyelonephritis (XGP) is an uncommon chronic destructive granulomatous inflammation of the kidney that can sometimes mimic other renal pathologies like tumours or infections. For this reason, it is also called “the great imitator”.This is the case of a 7-year old girl that presented to the hospital with right hip pain and a suspicious right sided abdominal lesion, thought initially to be a Wilms’ tumour and then an appe...
Source: Journal of Pediatric Surgery Case Reports - Category: Surgery Source Type: research
CONCLUSIONS: While controversies related to medical cannabis are expected to remain rampant, the validated vignettes may facilitate assessment of clinical practices, which is essential for a successful implementation of medical cannabis policies. These vignettes may additionally be used in medical training for appropriate patient selection for medical cannabis authorization. PMID: 31713356 [PubMed - indexed for MEDLINE]
Source: The Israel Medical Association Journal - Category: General Medicine Tags: Isr Med Assoc J Source Type: research
ConclusionMore research is needed to ensure health professionals working with adults who have chronic unrelenting musculoskeletal pain may safely recommend these exercises as one possible remedy for reducing intractable musculoskeletal pain.
Source: Current Rheumatology Reports - Category: Rheumatology Source Type: research
Authors: Hay ME, Connelly DM Abstract Physical inactivity and chronic back pain are prevalent among older adults; however, there are individuals who persist in exercising despite daily pain. This research explored the meaning of exercise in the lives of older adults with chronic back pain. Hermeneutic phenomenology, valuing everyday experiences and highlighting meaning, was employed. Individual in-depth interviews with 10 adults aged 65 years and older gathered rich descriptions of their experiences. Data collection and analyses were iterative processes. The experience of exercise was inextricably connected with ol...
Source: Journal of Aging and Physical Activity - Category: Geriatrics Tags: J Aging Phys Act Source Type: research
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