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The aim of this study was to determine simple risk factors for severe pain intensity (≥7 points on a numeric rating scale [NRS]), to analyse their relation to other patient-reported outcome measures and to develop a simple prediction model.
Learn More >Naltrexone reversibly blocks the effects of opioids and has been shown to decrease placebo analgesia. However, it is not clear (1) to what extent naltrexone affects pain modulation in a nontreatment context, for example, in response to pain cues or (2) how naltrexone given prior to pain-cue learning shapes pain responses. In a double-blind procedure prior to pain-cue conditioning, 30 healthy participants were randomized to receive an oral dose of naltrexone (50 mg) or inert pill. During functional magnetic resonance imaging, high and low pain pressures were paired with two different visual cues: a high pain cue and a low pain cue (learning sequence). During a test sequence, medium levels of pressure were used for both cues and the difference in subjective pain ratings following high and low pain cues was calculated. Results showed significant conditioned pain responses across groups (<.001); however, no significant difference between participants receiving naltrexone or inert pill (=.193). There was a significant correlation between the difference in high and low pain ratings during the learning sequence and the effect of high and low pain cues during the test sequence (r = .575, =.002). Functional magnetic resonance imaging analyses revealed no significant difference in brain activation between groups. Here, we demonstrate comparable learning of pain responses in participants treated with naltrexone or inert pill. The results point to the possibility that associative learning, and conditional responding to pain cues, is not dependent on endogenous opioids. Our results, using pain-cue conditioning to create reduced pain responses, contrast previous studies where opioid antagonists significantly reduced the placebo effect in treatment of pain.
Learn More >Cancer pain is often treated with opioids, a therapeutic regimen that can become a challenge in patients with an opioid use disorder (OUD). While use of the buprenorphine-naloxone combination is an effective medication-assisted treatment (MAT) for OUD, its use in pain patients with OUD has been controversial due to concerns that co-administration of buprenorphine can reduce or block analge-sia and precipitate opioid withdrawal in those patients requiring full opioid agonists. Data on its use in cancer pain patients are lack-ing. In this case series, the authors explore the frequency of buprenorphine-naloxone use and its outcomes in patients in a Compre-hensive Care Center (CCC) Pain Registry. OUD was deduced from an International Classification of Diseases (ICD-10) diagnostic code for opioid-related disorders recorded in the electronic medical records. Of 2,320 chronic cancer pain patients, 125 patients had ICD-10 code for opioid-related disorders, and 43 had a diagnosis of opioid abuse of whom 11 received buprenorphine-naloxone combina-tions. Eight patients on 18 (6-24) mg per day of buprenorphine-naloxone remained in therapy for 4 (2-7) years without opioid abuse relapse. This assessment was based on clinician's notes, the Prescription Monitoring Program, random urine drug screening, and the absence of Urgent Care Center visits for opioid withdrawal or overdose. When short-term opioids were administered for acute pain, these patients were able to taper down and stop them quickly without an opioid abuse relapse. Buprenorphine-naloxone was effec-tive as the sole analgesic in selected patients. Given its success at the CCC, buprenorphine-naloxone should be made available and strongly considered as a treatment for patients suffering from OUD during and following cancer treatment and when cancer pain re-duces or resolves.
Learn More >Telomere length, a measure of cellular aging, is inversely associated with chronic pain severity. While psychological resilience factors (e.g., optimism, acceptance, positive affect, active coping) are associated with lower levels of clinical pain and greater physical functioning, it is unknown whether resilience may buffer against telomere shortening in individuals with chronic pain. Additionally, a broader conceptualization of resilience that includes social and biobehavioral factors may improve our understanding of the relationship between resilience, chronic pain, and health outcomes. In individuals with and without chronic knee pain, we investigated whether: 1) psychological resilience would be positively associated with telomere length, and if 2) a broader conceptualization of resilience including social and biobehavioral factors would strengthen the association. Seventy-nine adults, 45-85 years of age, with and without knee pain completed demographic, health, clinical pain, psychological, social, and biobehavioral questionnaires. Resilience levels were determining by summing the total number of measures indicating resilience based on published clinical ranges and norms. Blood samples were collected and telomere length determined. In regression analyses controlling for sex, race, age, and characteristic pain intensity, greater psychological resilience and psychosocial/biobehavioral resilience were associated with longer telomeres (p = .0295 and p = .0116, respectively). When compared, psychosocial/biobehavioral resilience was significantly more predictive of telomere length than the psychological resilience (p < .0001). Findings are promising and encourage further investigations to enhance understanding of the biological interface of psychosocial and biobehavioral resilience factors in individuals with musculoskeletal chronic pain conditions.
Learn More >The glutamate type 1 transporter (GLT1) plays a major role in glutamate homeostasis in the brain. Although alterations of GLT1 activity have been linked to persistent pain, the significance of these changes is poorly understood. Focusing on the rostral ventromedial medulla, a key site in pain modulation, we examined the expression and function of GLT1 and related transcription factor kappa B-motif binding phosphoprotein (KBBP) in rats after adjuvant-induced hind paw inflammation.
Learn More >Medication-overuse headache (MOH) is a common chronic headache caused by overuse of headache analgesics. It has similarities with substance dependence disorders. The treatment of choice for MOH is withdrawal of the offending analgesics. Behavioral brief intervention treatment using methods adapted from substance misuse settings is effective. Here we investigate the severity of analgesics dependence in MOH using the Severity of Dependence Scale (SDS), validate the SDS score against formal substance dependence diagnosis based on the Diagnostic and Statistical Manual of Mental Disorders, 4th edition (DSM-IV) and examine whether the SDS predicts successful withdrawal.
Learn More >Accumulating evidence has demonstrated that the enhanced synaptic plasticity of nociceptive interneurons in the spinal dorsal horn is the basis of central sensitization in neuropathic pain. Our previous results demonstrate that Sirtuin 1 (SIRT1), a nicotinamide adenosine dinucleotide (NAD+)-dependent deacetylase, alleviates neuropathic pain in type 2 diabetes mellitus (T2DM) rats. SIRT1 has also been reported to regulate synaptic plasticity in different brain neurons. However, the role of SIRT1 in synaptic plasticity of spinal dorsal horn neurons remains unknown. In this study, we found that in the spinal dorsal horn of diabetic neuropathic pain (DNP) rats and db/db mice, decreased SIRT1 expression was accompanied by enhanced structural synaptic plasticity. The levels of post-synaptic density protein 95 (PSD-95), growth associated protein 43 (GAP43) and synaptophysin (SYP) increased in the spinal dorsal horn of DNP rats and db/db mice and in high glucose (HG)-cultured primary spinal neurons. Upregulation of spinal SIRT1 by SIRT1 activator SRT1720 relieved pain behavior, inhibited the enhanced structural synaptic plasticity in DNP rats and db/db mice, and decreased the levels of synapse-associated proteins in DNP rats, db/db mice, and HG-cultured spinal neurons. SIRT1 shRNA induced pain behavior, enhanced structural synaptic plasticity in normal rats, and increased synapse-associated proteins levels in normal rats and spinal neurons. Intrathecal AAV-Cre-EGFP into SIRT1 mice also induced pain behavior and enhanced synaptic plasticity of the spinal dorsal horn neurons. These results suggest that SIRT1 plays an important role in the progression of DNP by regulating synaptic plasticity of spinal dorsal horn neurons.
Learn More >Fibroblast Growth Factor Homologous Factors (FHF) constitute a subfamily of FGF proteins with four prototypes (FHF1-4; also known as FGF11-14). FHF proteins have been shown to bind directly to the membrane-proximal segment of the C-terminus in voltage-gated sodium channels (Nav), and regulate current density, availability, and frequency-dependent inhibition of sodium currents. Members of the FHF2 subfamily, FHF2A and FHF2B, differ in the length and sequence of their N-termini, and, importantly, differentially regulate Nav1.6 gating properties. Using immunohistochemistry, we show that FHF2 isoforms are expressed in adult dorsal root ganglion (DRG) neurons where they co-localize with Nav1.6 and Nav1.7. FHF2A and FHF2B show differential localization in neuronal compartments in DRG neurons, and levels of expression of FHF2 factors are down-regulated following sciatic nerve axotomy. Because Nav1.7 in nociceptors plays a critical role in pain, we reasoned that its interaction with FHF2 isoforms might regulate its current properties. Using whole-cell patch clamp in heterologous expression systems, we show that the expression of FHF2A in HEK293 cell line stably expressing Nav1.7 channels causes no change in activation, whereas FHF2B depolarizes activation. Both FHF2 isoforms depolarize fast-inactivation. Additionally, FHF2A causes an accumulation of inactivated channels at all frequencies tested due to a slowing of recovery from inactivation, whereas FHF2B has little effect on these properties of Nav1.7. Measurements of the Nav1.7 current in DRG neurons in which FHF2 levels are knocked down confirmed the effects of FHF2A on repriming, and FHF2B on activation, however FHF2A and B did not have an effect on fast inactivation. Our data demonstrates that FHF2 does indeed regulate the current properties of Nav1.7 and does so in an isoform and cell-specific manner.
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