Identification of patient characteristics influencing treatment outcomes is a top low back pain (LBP) research priority. Results from the STarT Back Trial support the effectiveness of prognostic stratified care for LBP compared to current best care, however patient characteristics associated with treatment response have not yet been explored. The purpose of this secondary analysis was to identify treatment-effect modifiers within the STarT Back Trial at 4 months follow-up (n=688). Treatment response was dichotomized using back-specific physical disability measured by the Roland-Morris Disability Questionnaire (≥7).
from The Journal of Pain http://ift.tt/2efMmoQ
via IFTTT
Monday, October 17, 2016
Mu and delta opioid receptor knockout mice show increased colonic sensitivity
Abstract
Background
Opiates act through opioid receptors to diminish pain. Here, we investigated whether mu (MOR) and delta (DOR) receptor endogenous activity assessed in the whole mouse body or in particular at peripheral receptors on primary nociceptive neurons, control colonic pain.
Methods
We compared global MOR and DOR receptor knockout (KO) mice, mice with a conditional deletion of MOR and DOR in Nav1.8-positive nociceptive primary afferent neurons (cKO), and control floxed mice of both genders for visceral sensitivity. Visceromotor responses to colorectal distension (CRD) and macroscopic colon scores were recorded on naïve mice and mice with acute colitis induced by 3% dextran sodium sulphate (DSS) for 5 days. Transcript expression for opioid genes and cytokines was measured by quantitative RT-PCR.
Results
Naïve MOR and DOR global KO mice show increased visceral sensitivity that was not observed in cKO mice. MOR and preproenkephalin (Penk) were the most expressed opioid genes in colon. MOR KO mice had augmented kappa opioid receptor and Tumour-Necrosis-Factor-α and diminished Penk transcript levels while DOR, preprodynorphin and Interleukin-1β were unchanged. Global MOR KO females had a thicker colon than floxed females. No alteration was detected in DOR mutant animals. A 5-day DSS treatment led to comparable hypersensitivity in the different mouse lines.
Conclusion
Our results suggest that mu and delta opioid receptor global endogenous activity but not activity at the peripheral Nav1.8 neurons contribute to visceral sensitivity in naïve mice, and that endogenous MOR and DOR tones were insufficient to elicit analgesia after 5-day DSS-induced colitis.
Significance
Knockout mice for mu and delta opioid receptor have augmented colon sensitivity in the CRD assay. It shows endogenous mu and delta opioid analgesia that may be explored as potential targets for alleviating chronic intestinal pain.
from European Journal of Pain http://ift.tt/2eaw0jW
via IFTTT
Effects of subtle cognitive manipulations on placebo analgesia – An implicit priming study
Abstract
Background
Expectancy is widely accepted as a key contributor to placebo effects. However, it is not known whether non-conscious expectancies achieved through semantic priming may contribute to placebo analgesia. In this study, we investigated if an implicit priming procedure, where participants were unaware of the intended priming influence, affected placebo analgesia.
Methods
In a double-blind experiment, healthy participants (n = 36) were randomized to different implicit priming types; one aimed at increasing positive expectations and one neutral control condition. First, pain calibration (thermal) and a credibility demonstration of the placebo analgesic device were performed. In a second step, an independent experimenter administered the priming task; Scrambled Sentence Test. Then, pain sensitivity was assessed while telling participants that the analgesic device was either turned on (placebo) or turned off (baseline). Pain responses were recorded on a 0–100 Numeric Response Scale.
Results
Overall, there was a significant placebo effect (p < 0.001), however, the priming conditions (positive/neutral) did not lead to differences in placebo outcome. Prior experience of pain relief (during initial pain testing) correlated significantly with placebo analgesia (p < 0.001) and explained 34% of placebo variance. Trait neuroticism correlated positively with placebo analgesia (p < 0.05) and explained 21% of placebo variance.
Conclusions
Priming is one of many ways to influence behaviour, and non-conscious activation of positive expectations could theoretically affect placebo analgesia. Yet, we found no SST priming effect on placebo analgesia. Instead, our data point to the significance of prior experience of pain relief, trait neuroticism and social interaction with the treating clinician.
Significance
Our findings challenge the role of semantic priming as a behavioural modifier that may shape expectations of pain relief, and affect placebo analgesia.
from European Journal of Pain http://ift.tt/2dI4l6O
via IFTTT
Friday, October 14, 2016
Stimulating TRPV1 externalization and synthesis in dorsal root ganglion neurons contributes to PGE2 potentiation of TRPV1 activity and nociceptor sensitization
Abstract
Background
Persistent peripheral sensitization contributes to chronic pain. Plasticity of nociceptive dorsal root ganglion (DRG) neurons (nociceptors) induced by pro-inflammatory mediators contributes to sensitization. Prostaglandin E2 (PGE2) enriched in injured tissues is known not only directly to sensitize DRG neurons, but also to potentiate sensitizing effects of other pain mediators such as capsaicin and its receptor transient receptor potential vanilloid-1 (TRPV1). It remains unknown whether PGE2 potentiates TRPV1 activity by stimulating its synthesis, cell surface and axonal trafficking in DRG neurons.
Methods
Combined biochemical, morphological, pharmacological and behavioral approaches have been used to address this issue in both in vitro and in vivo models.
Results
PGE2 increased TRPV1 externalization in cultured rat DRG neurons in a time- and concentration-dependent manner, an event blocked by an inhibitor of protein synthesis or anterograde export. EP1 and EP4, but not EP2 and EP3, mediated this event. EP1 agonist-induced TRPV1 externalization was suppressed by inhibitors of CaMKII, PLC, PKC and PKCε, while EP4 agonist-induced TRPV1 externalization by inhibitors of cAMP/PKA and ERK/MAPK. Pre-exposure to PGE2 potentiated release of calcitonin gene-related peptide from cultured DRG neurons evoked by subsequent capsaicin stimulation. This event was blocked by an inhibitor of protein synthesis or export, suggesting that PGE2-induced TRPV1 synthesis and externalization is coupled to enhanced TRPV1 activity. Pre-exposure to PGE2 not only prolonged tactile allodynia evoked by subsequent capsaicin challenge, but also increased TRPV1 levels in L4-6 DRG, sciatic nerves and plantar skin.
Conclusions
Our data indicate that facilitating TRPV1 synthesis, cell surface and axonal trafficking is a novel mechanism underlying PGE2 potentiation of TRPV1 activity.
from European Journal of Pain http://ift.tt/2dSkZ92
via IFTTT
Prescriptions of analgesics during complete disease trajectories in patients who are diagnosed with and die from cancer within the five-year period 2005–2009
Abstract
Background
Even though validation studies of the WHO analgesic ladder have indicated that the simple approach of the analgesic ladder can provide adequate pain control in most patients, prevalence studies have documented a high prevalence of pain in cancer patients. Little is known about how analgesics are actually prescribed for cancer pain. The aim of the study was to study prescriptions of analgesics during the entire disease trajectory in patients dying from cancer within five years of diagnosis.
Methods
Complete national data from the Norwegian Cancer Registry, the Norwegian Prescription Database, the Cause of Death Registry and Statistics Norway were used to study prescriptions of analgesics in a complete study population of all patients dying from cancer within five years of diagnosis in Norway from 2005 to 2009.
Results
Of a total of 10,977 subjects who received prescriptions for analgesics between diagnosis and death, 56% started analgesic treatment at step I of the analgesic ladder, 29% started at step II and 14% started at step III. Of the patients starting at step I, 28% continued to step II, 37% bypassed step II and moved directly to step III whereas the remaining 35% remained at step I. Approximately 60% received one or more dispensed prescription of a step III analgesic during the disease trajectory, whereas nearly 20% remained at step I and 20% at step II respectively.
Conclusion
The study indicates that clinicians seem to individually tailor analgesic treatment instead of applying the stepwise approach in the WHO analgesic ladder.
Significance
Complete national data covering the complete disease trajectory in cancer patients dying within five years of diagnosis. The majority of patients do not receive treatment in concordance with the stepwise approach suggested by the WHO analgesic ladder.
from European Journal of Pain http://ift.tt/2e6J4nY
via IFTTT
Applying causal mediation methods to clinical trial data: What can we learn about why our interventions (don't) work?
Abstract
Background
Many randomized controlled trials (RCTs) of psychosocial interventions for low back pain (LBP) have been found to have only small effects on disability outcomes. Investigations of the specific mechanisms that may lead to an improvement in outcome have therefore been called for.
Methods
We present an application of the causal inference approach to mediation analysis using the example of a cluster RCT in a primary care population with (sub)acute LBP randomized to either usual GP care (n = 171) or a minimal psychosocial intervention (n = 143). Mediation analysis explored the causal pathway between treatment allocation and disability at 3 months by considering pain catastrophizing, fear-avoidance beliefs, distress and receiving and following advice as potential mediators, all measured at 6 weeks. We have attempted to explain this approach to mediation analysis in a step-by-step manner to help clinical researchers apply this method more easily.
Results
In unadjusted mediation analyses, fear-avoidance beliefs were identified as a mediator of treatment on disability, with an indirect effect of −0.30 (95% CI: −0.86, −0.03), although this relationship was found to be non-significant after adjusting for age, gender and baseline scores. This finding supports the trial authors’ hypothesis that while fear-avoidance beliefs are important, this intervention may not have targeted them strongly enough to lead to change.
Conclusion
The use of mediation analysis to identify what factors may be part of the causal pathway between intervention and outcome, regardless of whether the intervention was successful, can provide useful information and insight into how to improve future interventions.
Significance
This study presents a step-by-step approach to mediation analysis using the causal inference framework to investigate why a psychosocial intervention for LBP was unsuccessful. Fear-avoidance beliefs were found to mediate the relationship between treatment and disability, although not when controlling for baseline scores.
from European Journal of Pain http://ift.tt/2dSihAh
via IFTTT
Pain expectations in neuropathic pain: Is it best to be optimistic?
Abstract
Background
Pain expectancy may be an important variable that has been found to influence the effectiveness of treatments for pain. Much of the literature supports a self-fulfilment perspective where expectations for pain relief predict the actual pain experienced. However, in conditions such as neuropathic pain (NeP) where pain relief is difficult to attain, expectations for pain relief could be unrealistic. The objective of this study was to investigate the relationship between realistic/unrealistic expectations and 6-month, post-treatment outcomes.
Methods
We performed a retrospective analysis of a large cohort of patients with NeP (n = 789) attending tertiary care centres to determine the association between unrealistic (both positive and negative) and realistic expectations with outcomes after multidisciplinary treatment. An expectation variable with three categories was calculated: realistic expectations were those whose expected reduction in pain was similar to the observed mean group reduction in pain, while optimistic and pessimistic expectations were those who over- or under-estimated the expected response to treatment, respectively. The association between baseline realistic/unrealistic expectations and 6-month pain-related disability, catastrophizing and psychological distress was assessed.
Results
Univariable analyses suggested that realistic expectations were associated with lower levels of disability, catastrophizing and psychological distress, compared to unrealistic expectations. However, after adjustment for baseline symptom severity, multivariable analysis revealed that patients with optimistic expectations had lower levels of disability, than those with realistic expectations. Those with pessimistic expectations had higher levels of catastrophizing and psychological distress at follow-up.
Conclusions
These findings are largely congruent with the self-fulfilment perspective to expectations.
Significance
This study defined realistic pain expectations with patient data. Examining the relationship between expectations between pain and disability in a large cohort of patients with neuropathic pain.
from European Journal of Pain http://ift.tt/2e6IHJN
via IFTTT
Subscribe to:
Posts (Atom)