Adrenergic dysregulation and pain with and without acute beta-blockade in women with fibromyalgia and temporomandibular disorder

Nociplastic pain mechanisms and toll-like receptors as promising targets for its management

ABSTRACT

Nociplastic pain, characterized by abnormal pain processing without an identifiable organic cause, affects a significant portion of the global population. Unfortunately, current pharmacological treatments for this condition often prove ineffective, prompting the need to explore new potential targets for inducing analgesic effects in patients with nociplastic pain. In this context, toll-like receptors (TLRs), known for their role in the immune response to infections, represent promising opportunities for pharmacological intervention because they play a relevant role in both the development and maintenance of pain. Although TLRs have been extensively studied in neuropathic and inflammatory pain, their specific contributions to nociplastic pain remain less clear, demanding further investigation. This review consolidates current evidence on the connection between TLRs and nociplastic pain, with a specific focus on prevalent conditions like fibromyalgia, stress-induced pain, sleep deprivation-related pain, and irritable bowel syndrome. In addition, we explore the association between nociplastic pain and psychiatric comorbidities, proposing that modulating TLRs can potentially alleviate both pain syndromes and related psychiatric disorders. Finally, we discuss the potential sex differences in TLR signaling, considering the higher prevalence of nociplastic pain among women. Altogether, this review aims to shed light on nociplastic pain, its underlying mechanisms, and its intriguing relationship with TLR signaling pathways, ultimately framing the potential therapeutic role of TLRs in addressing this challenging condition.

Adrenergic dysfunction in patients with myalgic encephalomyelitis/chronic fatigue syndrome and fibromyalgia: A systematic review and meta-analysis

BACKGROUND

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) and fibromyalgia (FM) are comorbid disorders with overlapping symptoms. Research highlights autonomic dysfunction compared to healthy individuals, particularly involving the sympathetic branch. While past reviews focused on neurophysiological assessments, this systematic review summarises biological adrenergic markers, offering deeper insights into the observed sympathetic dysfunction in ME/CFS and FM aiming to identify targetable pathophysiological mechanisms.

METHODS

A systematic search was performed on PubMed, Web of Science, Embase and Scopus. Studies investigating peripheral biological markers of adrenergic function in patients with ME/CFS or FM compared to healthy controls at baseline were included. Meta-analyses were performed using R statistical software.

RESULTS

This meta-analysis of 37 studies, encompassing 543 ME/CFS patients and 651 FM patients, compared with 747 and 447 healthy controls, respectively, revealed elevated adrenaline (SMD = .49 [.31-.67]; Z = 5.29, p < .01) and β1 adrenergic receptor expression (SMD = .79 [.06-1.52]; Z = 2.13; p = .03) in blood of ME/CFS patients at rest. Additionally, patients with ME/CFS had a greater increase in the expression of α2A adrenergic receptor (AR, SMD = .57 [.18-.97]; Z = 2.85, p < .01), β2 AR (SMD = .41 [.02-.81]; Z = 2.04; p = .04) and COMT (SMD = .42 [.03-.81]; Z = 2.11; p = .03) after exercise and an increased response of noradrenaline to an orthostatic test (SMD = .11 [-.47 to -.70]; Z = 2.10; p = .04), both found in blood. FM patients showed no significant differences at baseline but exhibited a diminished adrenaline response to exercise (SMD = -.79 [-1.27 to -.30]; Z = -3.14; p < .01).

CONCLUSION

This systematic review and meta-analysis revealed adrenergic dysfunction mainly in patients with ME/CFS. Higher baseline adrenaline levels and atypical responses to exercise in ME/CFS indicate that sympathetic dysfunction, underscored by adrenergic abnormalities, is more involved in the pathophysiology of ME/CFS rather than FM.

Reduced sympathetic activity is associated with the development of pain and muscle atrophy in a female rat model of fibromyalgia

Fibromyalgia (FM) is characterized by chronic widespread musculoskeletal pain accompanied by fatigue and muscle atrophy. Although its etiology is not known, studies have shown that FM patients exhibit altered function of the sympathetic nervous system (SNS), which regulates nociception and muscle plasticity. Nevertheless, the precise SNS-mediated mechanisms governing hyperalgesia and skeletal muscle atrophy in FM remain unclear. Thus, we employed two distinct FM-like pain models, involving intramuscular injections of acidic saline (pH 4.0) or carrageenan in prepubertal female rats, and evaluated the catecholamine content, adrenergic signaling and overall muscle proteolysis. Subsequently, we assessed the contribution of the SNS to the development of hyperalgesia and muscle atrophy in acidic saline-injected rats treated with clenbuterol (a selective β2-adrenergic receptor agonist) and in animals maintained under baseline conditions and subjected to epinephrine depletion through adrenodemedullation (ADM). Seven days after inducing an FM-like model with acidic saline or carrageenan, we observed widespread mechanical hyperalgesia along with loss of strength and/or muscle mass. These changes were associated with reduced catecholamine content, suggesting a common underlying mechanism. Notably, treatment with a β2-agonist alleviated hyperalgesia and prevented muscle atrophy in acidic saline-induced FM-like pain, while epinephrine depletion induced mechanical hyperalgesia and increased muscle proteolysis in animals under baseline conditions. Together, the results suggest that reduced sympathetic activity is involved in the development of pain and muscle atrophy in the murine model of FM analyzed.

Sympathetic innervation induces exosomal miR-125 transfer from osteoarthritic chondrocytes, disrupting subchondral bone homeostasis and aggravating cartilage damage in aging mice

INTRODUCTION

Osteoarthritis (OA) is a progressive disease that poses a significant threat to human health, particularly in aging individuals: Although sympathetic activation has been implicated in bone metabolism, its role in the development of OA related to aging remains poorly understood. Therefore, this study aimed to investigate how sympathetic regulation impacts aging-related OA through experiments conducted both in vivo and in vitro.

METHODS

To analyze the effect of sympathetic regulation on aging-related OA, we conducted experiments using various mouse models. These models included a natural aging model, a medial meniscus instability model, and a load-induced model, which were used to examine the involvement of sympathetic nerves. In order to evaluate the expression levels of β1-adrenergic receptor (Adrβ1) and sirtuin-6 (Sirt6) in chondrocytes of naturally aging OA mouse models, we performed assessments. Additionally, we investigated the influence of β1-adrenergic receptor knockout or treatment with a β1-adrenergic receptor blocker on the progression of OA in aging mice and detected exosome release and detected downstream signaling expression by inhibiting exosome release. Furthermore, we explored the impact of sympathetic depletion through tyrosine hydroxylase (TH) on OA progression in aging mice. Moreover, we studied the effects of norepinephrine(NE)-induced activation of the β1-adrenergic receptor signaling pathway on the release of exosomes and miR-125 from chondrocytes, subsequently affecting osteoblast differentiation in subchondral bone.

RESULTS

Our findings demonstrated a significant increase in sympathetic activity, such as NE levels, in various mouse models of OA including natural aging, medial meniscus instability, and load-induced models. Notably, we observed alterations in the expression levels of β1-adrenergic receptor and Sirt6 in chondrocytes in OA mouse models associated with natural aging, leading to an improvement in the progression of OA. Critically, we found that the knockout of β1-adrenergic receptor or treatment with a β1-adrenergic receptor blocker attenuated OA progression in aging mice and the degraded cartilage explants produced more exosome than the nondegraded ones, Moreover, sympathetic depletion through TH was shown to ameliorate OA progression in aging mice. Additionally, we discovered that NE-induced activation of the β1-adrenergic receptor signaling pathway facilitated the release of exosomes and miR-125 from chondrocytes, promoting osteoblast differentiation in subchondral bone.

CONCLUSION

In conclusion, our study highlights the role of sympathetic innervation in facilitating the transfer of exosomal miR-125 from osteoarthritic chondrocytes, ultimately disrupting subchondral bone homeostasis and exacerbating cartilage damage in aging mice. These findings provide valuable insights into the potential contribution of sympathetic regulation to the pathogenesis of aging-related OA.

The association of gene polymorphisms in catechol-O'methyltransferase (COMT) and β2-adrenergic receptor (ADRB2) with temporomandibular joint disorders

OBJECTIVE

Temporomandibular disorder (TMD) has a multifactorial etiology that includes environmental, psychological, and genetic factors. This study aimed to evaluate the possible relationship between polymorphisms in Catechol-O-methyltransferase (COMT) and β2-adrenergic receptor (ADRB2) genes with TMD.

DESIGN

This observational case-control study included 80 patients and 70 healthy controls. The diagnosis of TMD was made using the diagnostic criteria for TMD and the following TMD categories were used for the case group: muscular TMD and articular TMD (disc displacement and arthralgia). A genotyping study of gene polymorphisms in COMT (rs 9332377) and ADRB2 (rs20530449) was performed from genomic DNA isolated from blood. The chi-square test was used to analyze the relationships. P < 0.05 was accepted as a significant difference.

RESULTS

The polymorphic TT and CT genotype for COMT (rs rs9332377) was significantly higher in the articular TMD group while the non-polymorphic CC genotype was significantly lower in the articular TMD group (P < 0.05). Regarding ADRB2 (rs20530449), the polymorphic GG genotype was similarly considerably more common in the articular TMD group (p < 0.05). In addition, the T allele in the COMT (rs rs9332377) gene was found to be significantly higher in the articular TMD group (p < 0.05).

CONCLUSIONS

In the Turkish population, gene polymorphisms in COMT (rs9332377) and ADRB2 (rs2053044) were associated with articular TMD. This study supports the hypothesis that changes in COMT and ADRB2 genes may play a role in temporomandibular joint pain and predisposition to TMD.

Effect of propranolol on temporomandibular joint pain in repeatedly stressed rats

Stress substantially increases the risk of developing painful temporomandibular disorders (TMDs) by influencing the release of endogenous catecholamines. Propranolol, an antagonist of β-adrenergic receptors, has shown potential in alleviating TMD-associated pain, particularly when the level of catecholamines is elevated. The aim of this study was to explore whether intra-articular propranolol administration is effective in diminishing temporomandibular joint (TMJ) pain during repeated stress situations. Additionally, we investigated the effect of repeated stress on the expression of genes encoding β-adrenoceptors in the trigeminal ganglion. In the present study, rats were exposed to a stress protocol induced by sound, then to the administration of formalin in the TMJ (to elicit a nociceptive response), followed immediately afterward by different doses of propranolol, after which the analgesic response to propranolol was evaluated. We also assessed the levels of beta-1 and beta-2 adrenergic receptor mRNAs (Adrb1 and Adrb2, respectively) using reverse transcription-quantitative PCR (RT-qPCR). Our findings revealed that propranolol administration reduces formalin-induced TMJ nociception more effectively in stressed rats than in non-stressed rats. Furthermore, repeated stress decreases the expression of the Adrb2 gene within the trigeminal ganglion. The findings of this study are noteworthy as they suggest that individuals with a chronic stress history might find potential benefits from β-blockers in TMD treatment.

The Use of β-Blockers and the Risk of Undergoing a Knee Arthroplasty: A Nested Case-Control Study

BACKGROUND

Research has indicated that β-blockers may downregulate various inflammatory mediators that are involved in osteoarthritis (OA). The objective of this study was to analyze the likelihood of total knee arthroplasty (TKA) among patients with OA who were being treated with β-blockers.

METHODS

A nested case-control study was conducted with use of clinical records from our institutional database. We included patients who attended our outpatient clinic with a history of new-onset knee pain between 2010 and 2019. The case group included individuals who had undergone primary TKA between 2018 and 2019, whereas the control group included subjects who had not undergone TKA. Controls were matched by date of birth ±2 years, sex, calendar time (first outpatient visit ±1 year), and the grade of arthritis; the control-to-case ratio was 1:1. Adherence to β-blocker use was measured with use of the proportion of days covered (PDC) (i.e.,<0.25, ≥0.25 to <0.75, ≥0.75), and the cumulative effect was measured on the basis of the total number of years of treatment with β-blockers. A binary logistic regression analysis adjusted to potential confounders was carried out to assess the risk of TKA associated with the intake of β-blockers.

RESULTS

A total of 600 patients were included (300 in the case group and 300 in the control group). Compared with non-users, any use of β-blockers during the follow-up period was associated with a reduction in the likelihood of undergoing TKA (adjusted odds ratio [OR], 0.51; 95% confidence interval [CI], 0.34-0.77). The adjusted ORs for the use of selective β1-blockers and nonselective β1-blockers were 0.69 (95% CI, 0.36 to 1.31) and 0.42 (95% CI, 0.24 to 0.70), respectively. The adjusted ORs for any recent use, PDC of <0.25, PDC of ≥0.25 to <0.75, and PDC of ≥0.75 were 0.65 (95% CI, 0.51 to 0.99), 0.62 (95% CI, 0.21 to 1.85), 0.32 (95% CI, 0.09 to 1.22), and 0.55 (95% CI, 0.34 to 0.88), respectively. Regarding the cumulative effect of β-blockers, the adjusted ORs for the use for <1 year, ≥1 to <5 years, and ≥5 years were 0.41 (95% CI, 0.20 to 0.85), 0.52 (95% CI, 0.21 to 1.33), and 0.36 (95% CI, 0.22 to 0.60), respectively.

CONCLUSIONS

The use of nonselective β-blockers was associated with a lower likelihood of undergoing TKA. Patients treated for prolonged periods were at a lower likelihood for undergoing TKA.

LEVEL OF EVIDENCE

Prognostic Level III . See Instructions for Authors for a complete description of levels of evidence.

Coping with fibromyalgia during the COVID-19 pandemic: adjustment and wellbeing

OBJECTIVE

Fibromyalgia syndrome (FMS) is a chronic condition with symptoms known to be exacerbated by stress. Individuals with FMS may be experiencing particular distress under Covid-19 pandemic-related lifestyle restrictions. The present study examined wellbeing, perceived symptom change and coping in individuals with and without FMS during pandemic-related social lockdown in the UK.

DESIGN

Participants with a diagnosis of FMS (N = 390) and a general public sample with no FMS (N = 151) completed questionnaires at three time points.

MAIN OUTCOME MEASURES

BBC Wellbeing Scale, Cognitive-Emotional Regulation Questionnaire measure of coping, perception of extent to which symptoms have worsened or improved over time.

RESULTS

Contrary to expectations, FMS participants reported no worsening of symptoms and an increase in wellbeing over the study period. Non-FMS participants experienced worsening health symptoms and no change in wellbeing. Coping strategies involving positive reappraisal, refocussing and planning were positively associated with wellbeing in the FMS group.

CONCLUSION

The unpredictable symptom profile in FMS, and the regular readjustment this necessitates, may support a form of resilience which has been adaptive during the pandemic. The results have implications for supporting people with FMS, and potentially other chronic conditions, especially at times of stress.

Stress biomarkers in individuals with fibromyalgia syndrome: a systematic review with meta-analysis

ABSTRACT

Evidence suggests an involvement of hypothalamic-pituitary-adrenal (HPA) axis dysregulation in the development and maintenance of fibromyalgia syndrome (FMS). However, studies on the stress response via the HPA-axis in individuals with FMS show conflicting results. To better understand the relationship between FMS and HPA-axis dysregulation, we (1) systematically summarized the current level of evidence on HPA biomarkers in individuals with FMS compared with individuals without and (2) evaluated whether FMS is associated with a specific pattern of HPA dysregulation. The main outcome measures were cortisol, adrenocorticotropic hormone (ACTH), corticotropin-releasing hormone (CRH), epinephrine, and norepinephrine. A systematic search of MEDLINE, EMBASE, and PsychMed yielded 47 studies eligible for meta-analysis, including 1465 individuals with FMS and 1192 FMS-free controls. No main effect of FMS was found on altered levels of blood cortisol, ACTH, CRH, and epinephrine. Compared with controls, salivary and urinary cortisol levels were decreased in individuals with FMS, whereas blood levels of norepinephrine were increased. However, heterogeneity of data was high with significant evidence for publication bias. Overall, the data are compatible with association of FMS with adrenocortical hypofunction in the presence of increased sympathetic tone. However, the data are partially contradictory, so it must be assumed that the data are highly dependent on the respective study designs, patient samples, and analytical methods and do not necessarily demonstrate an abnormal HPA-axis function in FMS.

Investigation of temporomandibular disorders in patients with fibromyalgia syndrome: A case-control study

INTRODUCTION

The aim of this study is to compare the frequency of temporomandibular disorders and to examine the temporomandibular pain and functionality levels between healthy female participants and female patients diagnosed with fibromyalgia.

MATERIALS AND METHODS

Our study included 300 participants. Patients were evaluated according to the Diagnostic Criteria for Temporomandibular Disorders: Assessment Instruments (DC/TMD). While evaluating the patients using DC/TMD, TMD Pain Screener and Symptom questionnaire were used within the scope of Axis I, and Graded Chronic Pain Scale, Jaw Functional Limitation Scale-8 (JFLS-8), Patient Health Questionnaire (PHQ-4) and Oral Behaviors Checklist were applied.

RESULTS

Bruxism, tooth grinding and masseter hypertrophy were found to be significantly higher in fibromyalgia patients compared to healthy volunteers (p<0.001). The pain screener, JFLS-8, PHQ-4 and OBC scores and GCPS levels were found to be increased in the fibromyalgia group compared to healthy individuals (p<0.001). Considering the post-examination diagnoses of the participants, the diagnoses of myalgia (p=0.022) and disc displacement with reduction (p<0.001) were significantly higher than healthy individuals.

CONCLUSIONS

Fibromyalgia is a common pathology, therefore, TMD symptoms, which are more difficult to diagnose and often missed, should be questioned in fibromyalgia patients and should be kept in mind in the management of fibromyalgia patients.

Anesthesia-induced Takotsubo cardiomyopathy in trigeminal neuralgia: illustrative case

BACKGROUND

Takotsubo syndrome (TS) represents a form of nonischemic cardiomyopathy characterized by sudden and temporary weakening of the myocardium. Many data suggest a primary role for sympathetic overstimulation in its pathogenesis. Nevertheless, these correlates are less easily identified during anesthesia.

OBSERVATIONS

A 50-year-old female patient with a 4-year history of drug-resistant left trigeminal neuralgia. She was scheduled for surgical microvascular decompression. In the operating room, after induction of general anesthesia and oral intubation, the electrocardiogram revealed a significant ST segment elevation along with a sudden decrease in systolic blood pressure and heart rate. Administration of atropine caused a conversion into ventricular tachycardia. The advanced cardiac life support protocols were applied with prompt defibrillation and rapid recovery at sinus rhythm. A transthoracic echocardiogram revealed apical akinesia with ballooning of the left ventricle with a reduction of systolic function. An emergency coronary arteriography was performed, showing normal epicardial coronary vessels. After 4 days, echocardiography revealed normalization of the left ventricular function with improvement of the ejection fraction.

LESSONS

In patients affected by trigeminal neuralgia, chronic pain can lead to a state of adrenergic hyperactivation, which can promote TS during the induction of general anesthesia, probably through the trigeminocardiac reflex.

Differences in the regulatory mechanism of blood flow in the orofacial area mediated by neural and humoral systems

Marked blood flow (BF) changes mediated by the autonomic neural and humoral systems may be important for orofacial hemodynamics and functions. However, it remains questionable whether differences in the autonomic vasomotor responses mediated by neural and humoral systems exist in the orofacial area. This study examined whether there are differences in changes in the BF and vascular conductance (VC) between the masseter muscle and lower lip mediated by autonomic neural and humoral systems in urethane-anesthetized rats. Electrical stimulation of the central cut end of the lingual nerve elicited BF increases in the masseter (mainly cholinergic) and lower lip (mainly non-cholinergic), accompanied by an increase in arterial blood pressure (ABP), while cervical sympathetic trunk stimulation consistently decreased BF at both sites. The lingual nerve stimulation induced a biphasic change in the VC in the masseter, consisting of an initial decrease and a successive increase. This decrease in VC was positively correlated with changes in ABP and diminished by guanethidine. Cervical vagus nerve stimulation also induced BF increases at both sites; the increases were greater in the masseter than in the lower lip. Adrenal nerve stimulation and isoproterenol administration induced BF increases in the masseter but not in the lower lip. These results indicate that cholinergic parasympathetic-mediated hemodynamics evoked by trigeminal somatosensory inputs are closely related to ABP changes. The sympathetic nervous system, including the sympathoadrenal system and visceral inputs, may be more involved in hemodynamics in the muscles than in epithelial tissues in the orofacial area.

Sex-Related Effects of Adrenergic Drugs on Conditioned Pain Modulation: A Randomized Controlled Cross-Over Double-Blind Trial

Objective

Endogenous pain inhibition can be investigated using conditioned pain modulation (CPM). CPM efficacy has been reported to be influenced by various factors, such as gender and cardiovascular (autonomic) activity. The aim of this study is to describe the effect of pharmacological manipulations of autonomic activity on CPM efficacy.

Methods

Thirty healthy participants were enrolled to assess CPM efficacy in 4 experimental sessions. The first session consisted of the determination of baseline CPM effectiveness. The three following sessions were performed in a randomized order and consisted of the injection of (1) esmolol, (2) ephedrine, or (3) placebo, before the conditioning stimulus. Pain intensity induced by using a contact heat stimulation thermode was compared before and after a cold-pressure conditioning stimulus to evaluate CPM effectiveness.

Results

Our results show that inhibiting sympathetic nervous activity with esmolol did not have a significant effect on CPM. Conversely, enhancing sympathetic nervous activity with ephedrine increased CPM effectiveness in healthy women but decreased it in men.

Conclusions

Increasing sympathetic activity with adrenergic agonists, such as ephedrine, could improve CPM effectiveness in women. It will be interesting to verify if the same results are present in patients suffering from chronic pain and if adrenergic agonists could have better therapeutic effects in women showing reduced CPM effectiveness.

The contribution of autonomic mechanisms to pain in temporomandibular disorders: A narrative review

BACKGROUND

Temporomandibular disorders (TMD) are diagnosed based on symptom presentation and, like other functional pain disorders, often lack definitive pathology. There is a strong association between elevated stress levels and the severity of TMD-related pain, which suggests that alterations in autonomic tone may contribute to this pain condition.

OBJECTIVES

This narrative review examines the association between altered autonomic function and pain in TMD.

METHODS

Relevant articles were identified by searching PubMed and through the reference list of those studies.

RESULTS

TMD sufferers report an increased incidence of orthostatic hypotension. As in other chronic musculoskeletal pain conditions, TMD is associated with increased sympathetic tone, diminished baroreceptor reflex sensitivity and decreased parasympathetic tone. It remains to be determined whether ongoing pain drives these autonomic changes and/or is exacerbated by them. To examine whether increased sympathetic tone contributes to TMD-related pain through β₂ adrenergic receptor activation, clinical trials with the beta blocker propranolol have been undertaken. Although evidence from small studies suggested propranolol reduced TMD-related pain, a larger clinical trial did not find a significant effect of propranolol treatment. This is consistent with human experimental pain studies that were unable to demonstrate an effect of β₂ adrenergic receptor activation or inhibition on masticatory muscle pain. In preclinical models of temporomandibular joint arthritis, β₂ adrenergic receptor activation appears to contribute to inflammation and nociception, whereas in masticatory muscle, α₁ adrenergic receptor activation has been found to induce mechanical sensitization. Some agents used to treat TMD, such as botulinum neurotoxin A, antidepressants and α₂ adrenergic receptor agonists, may interact with the autonomic nervous system as part of their analgesic mechanism.

CONCLUSION

Even if dysautonomia turns out to be a consequence rather than a causative factor of painful TMD, the study of its role has opened up a greater understanding of the pathogenesis of this condition.

Gentle Touch Therapy, Pain Relief and Neuroplasticity at Baseline in Fibromyalgia Syndrome: A Randomized, Multicenter Trial with Six-Month Follow-Up

Background: Fibromyalgia (FM) is considered a stress-related disorder characterized mainly by chronic widespread pain. Its pathogenesis is unknown, but cumulative evidence points at dysfunctional transmitter systems and inflammatory biomarkers that may underlie the major symptoms of the condition. This study aimed to evaluate pain scores (primary outcome), quality of life, inflammatory biomarkers and neurotransmitter systems in women with FM (secondary outcomes) subjected to gentle touch therapy (GTT) or placebo. Methods: A total of 64 female patients with FM were randomly assigned to two groups, namely GTT (n = 32) or Placebo (n = 32). Clinical assessments were conducted at baseline and post-intervention with six-month follow-up. We measured serum catecholamines (dopamine), indolamines and intermediary metabolites (serotonin or 5-hydroxyindolacetic acid (5-HIAA)), as well as tetrahydrobiopterin (BH4), which is a cofactor for the synthesis of neurotransmitters and inflammatory biomarkers in women with FM. A group of healthy individuals with no intervention (control group) was used to compare biochemical measurements. Intervention effects were analyzed using repeated measures (RM) two-way ANOVA followed by Bonferroni post hoc test and mixed ANCOVA model with intention to treat. Results: Compared to placebo, the GTT group presented lower pain scores and brain-derived neurotrophic factor (BDNF) levels without altering the quality of life of women with FM. Changes in BDNF had a mediating role in pain. Higher baseline serum BDNF and 5-HIAA or those with a history of anxiety disorder showed a higher reduction in pain scores across time. However, women with higher serum dopamine levels at baseline showed a lower effect of the intervention across the observation period revealed by an ANCOVA mixed model. Conclusions: In conclusion, lower pain scores were observed in the GTT group compared to the placebo group without altering the quality of life in women with FM. Reductions in BDNF levels could be a mechanism of FM pain status improvement. In this sense, the present study encourages the use of these GTT techniques as an integrative and complementary treatment of FM.

Effect of Cognitive-Behavioral Therapy on Nocturnal Autonomic Activity in Patients with Fibromyalgia: A Preliminary Study

Objective: fibromyalgia is a complex chronic pain syndrome characterized by widespread musculoskeletal pain, insomnia and autonomic alterations. Cognitive-behavioral therapy (CBT) is regarded as a promising treatment in fibromyalgia, but its impact on autonomic function remains uncertain. In this research, we studied the effect of CBT on autonomic functions in fibromyalgia. Methods: Twenty-five participants underwent overnight polysomnographic recordings before and after CBT programs focused on pain (CBT-P) or a hybrid modality focused on pain and insomnia (CBT-C). Sleep quality, daily pain, depression and anxiety were assessed by self-reported questionnaires. We analyzed heart rate variability (HRV) using high-frequency power (HF) as a marker for parasympathetic activity, and low-frequency power (LF) and the LF/HF ratio as relative sympathetic markers during wakefulness and at each sleep stage. Results: After treatment, 14 patients (/25, 58.0%) reported improvement in their sleep: 6 in the CBT-P condition (/12, 50%), and 8 in the CBT-C condition (/13, 61.5%). We found that, regardless of the type of CBT, patients who reported improvement in sleep quality (n = 14, 58%) had an increase in HF during stages N2 (p < 0.05) and N3 (p < 0.05). These changes were related to improvement in sleep quality (N2, r = −0.43, p = 0.033) but not to pain, depression or anxiety. Conclusions: This study showed an improvement in parasympathetic cardiac control during non-rapid-eye-movement sleep following CBT in fibromyalgia participants who reported better sleep after this therapy. CBT may have a cardio-protective effect and HRV could be used as a sleep monitoring tool in fibromyalgia.

Stellate ganglion intervention for chronic pain: A review

Stellate ganglion (SG) intervention is currently widely being studied in many kinds of chronic pain. As one of the convenient ways to treat the sympathetic nervous system, the indications for stellate ganglion intervention (SGI) include complex regional pain syndrome, postherpetic neuralgia, cancer pain of different origins, orofacial pain, and so forth. SGI refers to the reversible or irreversible blocking of the cervical sympathetic trunk, cervical sympathetic ganglion, and their innervation range through noninvasive or minimally invasive treatment. Current treatment options include stellate ganglion block (SGB), SG pulsed radiofrequency, continuous radiofrequency treatment, and noninvasive SGB. In particular, SGB continues to be one of the most studied methods in chronic pain management. However, a single SGB usually provides only short-term effects; repeated SGB may result in complications such as hoarseness, light-headedness, and vessel or nerve injury. Meanwhile, the mechanism of SGI is still unclear. This review discusses the research progress of SGI methods, effectiveness, complications, and possible mechanisms in the management of chronic pain.

Altered electromyographic responses to emotional and pain information in awake bruxers: case-control study

OBJECTIVES

This study aims to investigate how emotional information and pain-related information affect the activity of the masticatory muscles in participants with awake bruxism and controls.

MATERIAL AND METHODS

Different videos and texts, with positive, negative, and neutral valence or related to pain, were presented to a sample of university students, while their electromyographic (EMG) activity around the masseter muscle and their skin conductance were recorded. Two groups were selected, with 24 subjects each: one group of subjects with definitive awake bruxism (confirmed by posterior EMG activity) who also suffered from moderate jaw discomfort, and another group of subjects without bruxism.

RESULTS

The results demonstrated that the subjects with definitive awake bruxism displayed greater muscular activity when presented videos and texts with negative valence, especially when related to pain, than the non-bruxist group.

CONCLUSIONS

This study supports the idea that persons with bruxism who also suffer moderate levels of jaw discomfort present greater bruxism activity when watching pain-related stimuli, and to a lesser extent when watching negative stimuli.

CLINICAL RELEVANCE

The increased muscular activity induced by negative and pain-related information might contribute to pain exacerbation and perpetuation in persons with bruxism who suffer from discomfort.

Efficacy and safety of propranolol for treatment of temporomandibular disorder pain: a randomized, placebo-controlled clinical trial

Propranolol is a nonselective beta-adrenergic receptor antagonist. A multicenter, randomized, double-blind, placebo-controlled, parallel-group, phase 2b trial enrolled participants aged 18 to 65 years with temporomandibular disorder myalgia to evaluate efficacy and safety of propranolol compared with placebo in reducing facial pain. Participants were randomized 1:1 to either extended-release propranolol hydrochloride (60 mg, BID) or placebo. The primary endpoint was change in facial pain index (FPI = facial pain intensity multiplied by facial pain duration, divided by 100). Efficacy was analyzed as a mean change in FPI from randomization to week 9 and as the proportion of participants with ≥30% or ≥50% reductions in FPI at week 9. Regression models tested for treatment-group differences adjusting for study site, sex, race, and FPI at randomization. Of 299 participants screened, 200 were randomized; 199 had at least one postrandomization FPI measurement and were included in intention-to-treat analysis. At week 9, model-adjusted reductions in mean FPI did not differ significantly between treatment groups (-1.8, 95% CL: -6.2, 2.6; P = 0.41). However, the proportion with a ≥30% reduction in FPI was significantly greater for propranolol (69.0%) than placebo (52.6%), and the associated number-needed-to-treat was 6.1 (P = 0.03). Propranolol was likewise efficacious for a ≥50% reduction in FPI (number-needed-to-treat = 6.1, P = 0.03). Adverse event rates were similar between treatment groups, except for more frequent fatigue, dizziness, and sleep disorder in the propranolol group. Propranolol was not different from placebo in reducing mean FPI but was efficacious in achieving ≥30% and ≥50% FPI reductions after 9 weeks of treatment among temporomandibular disorder participants.

β-blocker prescription is associated with lower cumulative risk of knee osteoarthritis and knee pain consultations in primary care: a propensity score matched cohort study

Objectives

To examine the association between β-blocker prescription and first primary-care consultation for knee OA, hip OA, knee pain and hip pain.

Methods

Data source: Clinical Practice Research Datalink. Participants aged ≥40 years in receipt of new oral β-blocker prescriptions were propensity score (PS) matched to an unexposed control. Cox proportional hazard ratios (HRs) and 95% CIs were calculated, and adjusted for non-osteoporotic fractures, number of primary-care consultations for knee or hip injury, and, the number of primary-care consultations, out-patient referrals and hospitalizations in the 12 months preceding cohort entry. Analysis was stratified according to β-blocker class and for commonly prescribed drugs. P < 0.05 was considered statistically significant.

Results

A total of 111 718 β-blocker–exposed participants were 1:1 PS matched to unexposed controls. β-blocker prescription was associated with reduced cumulative risk of knee OA, knee pain, and hip pain consultations [with a HR (95% CI) of 0.90 (0.83, 0.98), 0.88 (0.83, 0.92) and 0.85 (0.79, 0.90), respectively]. Propranolol and atenolol were associated with a lower incidence of knee OA and knee pain consultations with a HR of between 0.78 and 0.91. β-blockers were associated with reduced incidence of consultation for large-joint lower-limb OA/pain as a composite outcome, defined as the earliest of knee OA, knee pain, hip OA or a hip pain consultation [with a HR (95% CI) of 0.87 (0.84, 0.90)].

Conclusion

Commonly used β-blockers have analgesic properties for musculoskeletal pain. Atenolol might be a therapeutic option for OA and cardiovascular co-morbidities in which β-blockers are indicated, while propranolol may be suitable for people with co-morbid anxiety. A confirmatory randomized controlled trial is needed before clinical practice is changed.

Adrenergic signalling in osteoarthritis

Adrenoceptors (ARs) mediate the effects of the sympathetic neurotransmitters norepinephrine (NE) and epinephrine (E) in the human body and play a central role in physiologic and pathologic processes. Therefore, ARs have long been recognized as targets for therapeutic agents, especially in the field of cardiovascular medicine. During the past decades, the contribution of the sympathetic nervous system (SNS) and particularly of its major peripheral catecholamine NE to the pathogenesis of osteoarthritis (OA) attracted growing interest. OA is the most common degenerative joint disorder worldwide and a disease of the whole joint. It is characterized by progressive degradation of articular cartilage, synovial inflammation, osteophyte formation, and subchondral bone sclerosis mostly resulting in chronic pain. The subchondral bone marrow, the periosteum, the synovium, the vascular meniscus and numerous tendons and ligaments are innervated by tyrosine hydroxylase-positive (TH+) sympathetic nerve fibers that release NE into the synovial fluid and cells of all abovementioned joint tissues express at least one out of nine AR subtypes. During the past decades, several in vitro studies explored the AR-mediated effects of NE on different cell types in the joint. So far, only a few studies used animal OA models to investigate the contribution of distinct AR subtypes to OA pathogenesis in vivo. This narrative review shortly summarizes the current background knowledge about ARs and their signalling pathways at first. In the second part, we focus on recent findings in the field of NE-induced AR-mediated signalling in different joint tissues during OA pathogenesis and at the end, we will delineate the potential of targeting the adrenergic signalling for OA prevention or treatment. We used the PubMed bibliographic database to search for keywords such as 'joint' or 'cartilage' or 'synovium' or 'bone' and 'osteoarthritis' and/or 'trauma' and 'sympathetic nerve fibers' and/or 'norepinephrine' and 'adrenergic receptors / adrenoceptors' as well as 'adrenergic therapy'.

Therapeutic Agents for the Treatment of Temporomandibular Joint Disorders: Progress and Perspective

Temporomandibular joint disorders (TMD) are a common health condition caused by the structural or functional disorders of masticatory muscles and the temporomandibular joint (TMJ). Abnormal mandibular movement in TMD patients may cause pain, chronic inflammation, and other discomfort, which could be relieved by a variety of drugs through various delivery systems. In this study, we summarized commonly used therapeutic agents in the management of TMD as well as novel bioactive molecules in preclinical stage and clinical trials. The emerging therapy strategies such as novel intra-TMJ delivery systems and implants based on tissue engineering are also discussed. This comprehensive review will strengthen our understanding of pharmacological approaches for TMD therapy.

The relationship between chronic pain, prehypertension, and hypertension. A population-based cross-sectional survey in Al-Kharj, Saudi Arabia

Background: Chronic pain and hypertension are highly prevalent in both developing and developed countries. Although they may appear to be two separate phenomena, several studies in developed countries have found them associated at the population level. Studies in developing countries are scarce and association between pain with prehypertension are rarely explored. The objective of this study was to explore the potential association between prehypertension, hypertension, and chronic pain in a Saudi population.Methods: A cross-sectional general population-based study was conducted on a random sample of employees and university students over a period of 6 months from January 2016 to June 2016 in Al Kharj, Saudi Arabia. A total of 1200 general population adults (aged 18 years and above) were invited to participate in the study.Results: With a response rate of 85.9%, 1031 individuals were included in the final analysis. Among the general population of Al-Kharj, statistically significant association was found between age and chronic pain [Odds ratio (OR) = 1.764 [95% C.I. = 1.391-1.927], P < 0.0001] and between hypertension and chronic pain [(OR) = 1.039 [95% C.I. = 1.018-1.060], P < 0.0001], respectively. The association between prehypertension and chronic pain was not statistically significant [(OR) = 1.211 [95% C.I. = 0.879-1.668, P = 0.243].Conclusion: Results of this survey suggests a statistically significant relationship between hypertension (but not prehypertension) and chronic pain. The temporality of the relationship between hypertension and chronic needs to be explored in future longitudinal studies.

Neuromodulation of bone: Role of different peptides and their interactions (Review)

Our understanding of the skeletal system has been expanded upon the recognition of several neural pathways that serve important roles in bone metabolism and skeletal homeostasis, as bone tissue is richly innervated. Considerable evidence provided by in vitro, animal and human studies have further elucidated the importance of a host of hormones and local factors, including neurotransmitters, in modulating bone metabolism and osteo-chondrogenic differentiation, both peripherally and centrally. Various cells of the musculoskeletal system not only express receptors for these neurotransmitters, but also influence their endogenous levels in the skeleton. As with a number of physiological systems in nature, a neuronal pathway regulating bone turnover will be neutralized by another pathway exerting an opposite effect. These neuropeptides are also critically involved in articular cartilage homeostasis and pathogenesis of degenerative joint disorders, such as osteoarthritis. In the present Review, data on the role of several neuronal populations in nerve-dependent skeletal metabolism is examined, and the molecular events involved are explored, which may reveal broader relationships between two apparently unrelated organs.

Temporomandibular disorders: a review of current concepts in aetiology, diagnosis and management

Temporomandibular disorders (TMD) is a collective term for a group of musculoskeletal conditions involving pain and/or dysfunction in the masticatory muscles, temporomandibular joints (TMJ) and associated structures. It is the most common type of non-odontogenic orofacial pain and patients can present with pain affecting the face/head, TMJ and or teeth, limitations in jaw movement, and sounds in the TMJ during jaw movements. Comorbid painful and non-painful conditions are also common among individuals with TMD. The diagnosis of TMD have significantly improved over time with the recent Diagnostic Criteria for TMD (DC/TMD) being reliable and valid for most common diagnoses, and an efficient way to communicate in multidisciplinary settings. This classification covers 12 most common TMD, including painful (myalgia, arthralgia and headache attributed to TMD) as well as the non-painful (disc displacements, degenerative joint disease and subluxation) TMD diagnoses. Recent studies have demonstrated that the pathophysiology of common painful TMD is biopsychosocial and multifactorial, where no one factor is responsible for its development. Importantly, research has suggested different predisposing, initiating and perpetuating factors, including both peripheral and central mechanisms. This is an active field of investigation and future studies will not only seek to clarify specific causal pathways but translate this knowledge into mechanism-directed diagnosis and treatment. In accordance with this complex aetiology, current evidence supports primarily conservative multidisciplinary treatment including self-management strategies, behavioural therapy, physical therapy and pharmacotherapy. The aim of this review is to present an overview of most recent developments in aetiology, pathophysiology, diagnosis and management of TMD.

Contribution of Baroreceptor Function to Pain Perception and Perioperative Outcomes

Baroreceptors are mechanosensitive elements of the peripheral nervous system that maintain homeostasis by coordinating physiologic responses to external and internal stimuli. While it is recognized that carotid and cardiopulmonary baroreceptor reflexes modulate autonomic output to mitigate excessive fluctuations in arterial blood pressure and to maintain intravascular volume, increasing evidence suggests that baroreflex pathways also project to key regions of the central nervous system that regulate somatosensory, somatomotor, and central nervous system arousal. In addition to maintaining autonomic homeostasis, baroreceptor activity modulates the perception of pain, as well as neuroimmune, neuroendocrine, and cognitive responses to physical and psychologic stressors. This review summarizes the role that baroreceptor pathways play in modulating acute and chronic pain perception. The contribution of baroreceptor function to postoperative outcomes is also presented. Finally, methods that enhance baroreceptor function, which hold promise in improving postoperative and pain management outcomes, are presented.

Determination of the increased risk of developing atrial fibrillation in fibromyalgia syndrome

INTRODUCTION

Atrial fibrillation (AF) is the leading cause of ischemic stroke and is one of the most common arrhythmias. Previous studies have shown that impaired diastolic functions, P wave dispersion (Pd), and prolonged atrial conduction times (ACT) are associated with increased incidence of atrial fibrillation (AF). The aim of this study was to evaluate diastolic functions, Pd, and ACT in fibromyalgia syndrome (FMS) patients to determine whether there is an increase in the risk of developing AF.

METHODS

The study included a total of 140 female patients (70 FMS group, 70 healthy control group). Pd was evaluated using 12 lead electrocardiography (ECG), and diastolic functions and ACT with echocardiography. The ECG and echocardiographic evaluations were performed by different cardiologists blinded to the clinical information of the subjects.

RESULTS

There was no difference between the two groups in laboratory and clinical parameters. Patients with FMS had significantly higher echocardiographic parameters of ACT known as left-sided intra-atrial (13.9 ± 5.9 vs. 8.1 ± 1.8, p < 0.001), right-sided intra-atrial (21.9 ± 8.2 vs. 10.4 ± 3.5, p < 0.001) and interatrial [40 (25-64) ms vs. 23 (14-27) ms p < 0.001] electromechanical interval (EMI) compared with the control group. Pd was significantly greater in the FMS group compared with the control group [46 (29-62) ms vs. 32 (25-37) ms, p < 0.001]. In the FMS group, there was no significant relationship of the echocardiographic parameters of ACT, Pmax and Pd with age, E/A ratio and deceleration time (DT); while all these five parameters were significantly correlated with left atrial dimension, isovolumetric relaxation time (IVRT), fibromyalgia impact questionnaire (FIQ) and visual analogue scale (VAS). There was a strong correlation between FIQ and VAS and echocardiographic parameters of ACT, Pmax and Pd.

CONCLUSIONS

Impaired diastolic functions, an increase in Pd, and prolongation of ACT were observed in FMS. Current disorders are thought to be associated with an increased risk of AF in FMS. The risk of developing AF increases with the severity of FMS and clinical progression.

Coexistence of Alterations of Gastrointestinal Function and Mechanical Allodynia in the Reserpine-Induced Animal Model of Fibromyalgia

BACKGROUND

Fibromyalgia (FM) is a disorder characterized by widespread chronic pain as core symptom and a broad range of comorbidities. Despite the prevalence of gastrointestinal (GI) comorbidities in patients with FM, GI functions have rarely been investigated in animal models of FM.

AIMS

The purpose of the present study is to investigate the coexistence of alterations of GI function in the reserpine-induced myalgia (RIM) rat, a validated FM model associated with disruption of monoamine system.

METHODS

Paw withdrawal threshold (von Frey hair test) was assessed as pain-associated indicator. Gastric emptying (¹³C breath test), small intestinal transit (charcoal meal test), and fecal water content were investigated as GI functions.

RESULTS

The specific regimen of reserpine for the RIM rat, i.e., 1 mg/kg s.c., once daily for three consecutive days, caused a reduction of paw withdrawal threshold (i.e., mechanical allodynia) on days 3, 5, and 7 after the first injection. The ¹³CO₂ excreted from the RIM rat was significantly increased on day 7. The RIM rat exhibited an acceleration of small intestinal transit on day 5. Fecal water content collected from the RIM rat was significantly increased on days 3 and 5. The amount of noradrenaline was significantly decreased in GI tissues on days 3, 5, and 7 in the RIM rat. Conclusions This study revealed that accelerated gastric emptying, accelerated small intestinal transit, and increase in fecal water content coexist with mechanical allodynia in the RIM rat, simulating the coexistence of chronic pain and alterations of GI function in patients with FM.

Brain Responses in CFS and TMD to Autonomic Challenges: An Exploratory fMRI Study

INTRODUCTION

Dysfunction of the autonomic nervous system (ANS) is seen in chronic fatigue syndrome (CFS) and temporomandibular disorders (TMDs). Both conditions have poorly understood pathophysiology. Several brain structures that play a role in pain and fatigue, such as the insular cortex and basal ganglia, are also implicated in autonomic function.

OBJECTIVES

ANS dysfunction may point to common neurophysiologic mechanisms underlying the predominant symptoms for CFS and TMD. No studies to date have investigated the combination of both conditions. Thus, our aim was to test whether patients with CFS with or without TMD show differences in brain responses to autonomic challenges.

METHODS

In this exploratory functional imaging study, patients with CFS who screened positive for TMD (n = 26), patients who screened negative for TMD (n = 16), and age-matched control participants (n = 10) performed the Valsalva maneuver while in a 3-T magnetic resonance imaging scanner. This maneuver is known to activate the ANS.

RESULTS

For all 3 groups, whole-brain F test showed increased brain activation during the maneuver in the superior and inferior frontal gyri, the left and right putamen and thalamus, and the insular cortex. Furthermore, group contrasts with small-volume correction showed that patients with CFS who screened positive for TMD showed greater activity in the left insular cortex as compared with patients who screened negative and in the left caudate nucleus as compared with controls.

CONCLUSION

Our results suggest that increased activity in the cortical and subcortical regions observed during autonomic challenges may be modulated by fatigue and pain. ANS dysfunction may be a contributing factor to these findings, and further work is required to tease apart the complex relationship among CFS, TMD, and autonomic functions.

KNOWLEDGE TRANSFER STATEMENT

Brain activity related to activation of the autonomic nervous system in patients with chronic fatigue syndrome who screened positive for painful temporomandibular disorder was greater than in patients who screened negative; activity was seen in brain regions associated with autonomic functions and pain. These findings suggest that autonomic dysfunction may play a role in the pathophysiology of both conditions, explain some of the apparent comorbidity between them, and offer avenues to help with treatment.

Do β-adrenoreceptor blocking drugs associate with reduced risk of symptomatic osteoarthritis and total joint replacement in the general population? A primary care-based, prospective cohort study using the Clinical Practice Research Datalink

INTRODUCTION

To investigate if β-adrenoreceptor blocking drug (β-blocker) prescription reduces the risk of knee or hip osteoarthritis, total joint replacement and analgesic prescription.

SETTING

Primary care.

METHODS AND ANALYSIS

This is a cohort study using data from the Clinical Practice Research Datalink. Two separate analyses will be performed. Study 1 will be on the association between β-blocker prescription and incident knee/hip osteoarthritis. Inclusion criteria will be age ≥40 years. Exposed participants will be those with ≥2 continuous β-blocker prescriptions, and the index date will be the date of the first prescription of β-blocker. Unexposed participants will include up to four controls matched for age, sex, general practice surgery and propensity score for β-blocker prescription. Exclusion criteria will include contraindications to β-blockers, consultations for osteoarthritis or potent analgesic prescription before the index date. Outcomes will be knee osteoarthritis (primary outcome), hip osteoarthritis, knee pain and hip pain. Study 2 will be on the association between β-blocker prescription and total joint replacement and analgesic prescription in people with osteoarthritis. Inclusion criteria will be age ≥40 years, knee or hip osteoarthritis, and index date will be as in study 1. Unexposed participants will be as in study 1, additionally matched for consultation for knee or hip osteoarthritis prior to the index date. Exclusion criteria will include contraindications to β-blockers and osteoarthritis in other joints prior to the index date. Outcomes will be total knee replacement (primary outcome), total hip replacement and new analgesic prescription.

STATISTICAL ANALYSIS

Kaplan-Meier curves will be plotted, and Cox proportional HRs and 95% CIs will be calculated. Stratified analysis will be performed by class of β-blocker, intrinsic sympathomimetic effect and indication(s) for prescription.

ETHICS AND DISSEMINATION

This study was ethically approved by the Independent Scientific Advisory Committee of the Medicines and Healthcare Authority (Ref 18_227R). The results of this study will be published in peer-reviewed journals and presented at conferences.

SUMMARY

This prospective cohort study will evaluate the analgesic potential of commonly used drugs for osteoarthritis pain.

Evidence of Altered Trigeminal Nociception in an Animal Model of Fibromyalgia

Objective

Fibromyalgia (FM) is a debilitating chronic condition that significantly affects quality of life. A strong association has been demonstrated between FM and chronic pain in the trigeminal region in clinical studies. This study was performed to evaluate the response to acute and chronic noxious stimuli applied to the facial region.

Methods

Adult male Wistar rats (250-270 g, N = 10 for each group) were used in the current study. A subchronic swim stress model was used as the animal model of FM. Anxiety-like behaviors and response to acute and chronic noxious stimuli were assayed using the elevated plus maze, eye wiping test, and orofacial formalin test, respectively. Balance and motor function were evaluated using rotarod and wire grip tests.

Results

An increased anxiety-like behavior was observed in swim stress rats in comparison with control and sham subjects. Response to acute and chronic noxious stimuli in the trigeminal region was increased in the stressed rats. Motor and balance function were not altered following stress.

Conclusions

Results of the current study demonstrated a hyperalgesic state in the trigeminal region in a possible animal model of FM. This study provides a reliable animal model for further research on the possible mechanisms of orofacial pain in FM.

Evaluation of Ventricular Diastolic Function in Patients With Fibromyalgia Syndrome

Objectives

This study aims to compare the diastolic functions between fibromyalgia (FM) patients and control subjects by using transthoracic echocardiography.

Patients and methods

This case-control and cross-sectional study included 34 female FM patients (mean age 43.6±8.2 years; range 28 to 57 years), who were diagnosed by The American College of Rheumatology 1990 Criteria for the Classification of Fibromyalgia and defined as the FM group. A control group was defined consisting of 30 healthy females (mean age 41.2±9.1 years; range 22 to 54 years). Echocardiography findings of the groups were compared.

Results

The body mass index and mean disease duration of the FM group were 25.37±2.71 kg/m2 and 12.24 months, respectively. The body mass index of the control group was 25.58±1.49 kg/m2. There was no significant difference between the groups in terms of age and body mass index. Isovolumetric relaxation time and mitral E-wave deceleration time values were significantly higher in the FM group than in the control group (p=0.047, p=0.003, respectively).

Conclusion

Isovolumetric relaxation time and mitral valve deceleration time are significantly prolonged in FM patients compared with healthy subjects. Female patients with FM seem to be under risk of impaired relaxation and diastolic function of the left ventricle.

Catecholamine and Indolamine Pathway: A Case-Control Study in Fibromyalgia

OBJECTIVES

Fibromyalgia (FM) is a complex syndrome characterized by widespread pain. Its etiology is unclear, and diagnosis is difficult. The aim of this study was to assess plasma levels of monoamine neurotransmitters (catecholamines, indolamines, and intermediate metabolites) in patients with FM and healthy controls to investigate possible alterations in the metabolism of these molecules in FM. We also examined potential relationships between monoamine neurotransmitters and clinical features of FM. The predictive value of these molecules in FM was determined by receiver operating characteristic analysis.

METHOD

We measured plasma catecholamines (epinephrine, norepinephrine, and dopamine), as well as indolamines and intermediary metabolites (serotonin or 5-hydroxytryptamine [5-HT], 5-hydroxyindolacetic acid [5-HIAA], 5-hydroxytryptophan [5-HTP], and N-acetyl-5-hydroxytryptamine [Nac-5-HT]) in 35 women with FM and 12 age-matched healthy women.

RESULTS

Higher levels of norepinephrine and lower levels of dopamine, 5-HT, 5-HIAA, and 5-HTP were found in women with FM in comparison with controls. Epinephrine and Nac-5-HT levels did not differ significantly between groups. Higher norepinephrine levels were associated with worse physical health status in FM patients. Also, plasma norepinephrine levels > 694.69 pg/ml might be an accurate predictor of FM.

CONCLUSIONS

These findings show evidence of the dysregulation of the catecholamine and indolamine pathway in patients with FM, which may contribute to the physiopathology of this syndrome. In addition, the determination of plasma norepinephrine levels could help in the FM diagnosis.

The effects of propranolol on heart rate variability and quantitative, mechanistic, pain profiling: a randomized placebo-controlled crossover study

Background and aims

The autonomic nervous system (ANS) is capable of modulating pain. Aberrations in heart rate variability (HRV), reflective of ANS activity, are associated with experimental pain sensitivity, chronic pain, and more recently, pain modulatory mechanisms but the underlying mechanisms are still unclear. HRV is lowered during experimental pain as well as in chronic pain conditions and HRV can be increased by propranolol, which is a non-selective β-blocker. Sensitization of central pain pathways have been observed in several chronic pain conditions and human mechanistic pain biomarkers for these central pain pathways include temporal summation of pain (TSP) and conditioned pain modulation (CPM). The current study aimed to investigate the effect of the β-blocker propranolol, and subsequently assessing the response to standardized, quantitative, mechanistic pain biomarkers.

Methods

In this placebo-controlled, double-blinded, randomized crossover study, 25 healthy male volunteers (mean age 25.6 years) were randomized to receive 40 mg propranolol and 40 mg placebo. Heart rate, blood pressure, and HRV were assessed before and during experimental pain tests. Cuff pressure pain stimulation was used for assessment of pain detection (cPDTs) and pain tolerance (cPTTs) thresholds, TSP, and CPM. Offset analgesia (OA) was assessed using heat stimulation.

Results

Propranolol significantly reduced heart rate (p<0.001), blood pressure (p<0.02) and increased HRV (p<0.01) compared with placebo. No significant differences were found comparing cPDT (p>0.70), cPTT (p>0.93), TSP (p>0.70), OA-effect (p>0.87) or CPM (p>0.65) between propranolol and placebo.

Conclusions

The current study demonstrated that propranolol increased HRV, but did not affect pressure pain sensitivity or any pain facilitatory or modulatory outcomes.

Implications

Analgesic effects of propranolol have been reported in clinical pain populations and the results from the current study could indicate that increased HRV from propranolol is not associated with peripheral and central pain pathways in healthy male subjects.

Quantitative Sensory Testing, Antihistamines, and Beta-Blockers for Management of Persistent Breast Pain: A Case Series

BACKGROUND

It is not uncommon for mothers to have persistent pain with breastfeeding beyond the first few weeks after birth. Persistent pain can be multifactorial, with neuropathic pain maintained by central sensitization being one dimension. Our knowledge in delineating categories of persistent pain is simple and not very sophisticated.

METHODS

We have developed and tested a Lactation Quantitative Sensory Test (L-QST) to quantify the neuropathic component of persistent breastfeeding pain. We present three case reports of neuropathic breastfeeding pain and treatment, and we discuss the potential role of histamine and catecholamines in persistent breastfeeding-associated pain.

CONCLUSIONS

The L-QST can be a useful tool to quantify neuropathic pain. Further studies are needed to test inter-observer reliability and reproducibility of this tool. Antihistamines can be considered for treating persistent pain in breastfeeding women with a history of allergy or atopy, and beta-blockers may be helpful in women with multiple pain disorders.

Salivary stress biomarkers and anxiety symptoms in children with and without temporomandibular disorders

The etiology of temporomandibular disorders (TMD), which are considered as a heterogeneous group of psychophysiological disturbances, remains a controversial issue in clinical dentistry. This study aimed to evaluate whether the salivary alpha-amylase (sAA), cortisol levels, and anxiety symptoms differ between children with and without TMD. Initially, 316 young subjects were screened in public schools (nonreferred sample); 76 subjects aged 7-14 years were selected and comprised the TMD and control groups with 38 subjects each matched by sex, age, and the presence/absence of sleep bruxism. Four saliva samples were collected: upon waking, 30 min and 1 h after awakening (fasting), and at night (at 8 PM) on 2 alternate days to examine the diurnal profiles of cortisol and sAA. Anxiety symptoms were screened using the Multidimensional Anxiety Scale for Children (MASC-Brazilian version). Shapiro-Wilk test, Student's t-test/Mann-Whitney U test, and correlation tests were used for data analysis. No significant differences were observed in the salivary cortisol area under the curve (AUCG mean ± SD = 90.22 ± 63.36 × 94.21 ± 63.13 µg/dL/min) and sAA AUCG (mean ± SD = 2544.52 ± 2142.00 × 2054.03 ± 1046.89 U/mL/min) between the TMD and control groups, respectively (p > 0.05); however, the clinical groups differed in social anxiety domain (t = 3.759; CI = 2.609, 8.496), separation/panic (t = 2.243; CI = 0.309, 5.217), physical symptoms (U = 433.500), and MASC total score (t = -3.527; CI = -23.062, -6.412), with a power of the test >80% and large effect size (d = 0.80), with no significant correlation between the MASC total score, cortisol, and sAA levels. Although children with TMD scored higher in anxiety symptoms, no difference was observed in the salivary stress biomarkers between children with and without TMD.

Biopsychosocial influence on shoulder pain: Rationale and protocol for a pre-clinical trial

BACKGROUND

Chronic musculoskeletal pain conditions are a prevalent and disabling problem. Preventing chronic musculoskeletal pain requires multifactorial treatment approaches that address its complex etiology. Prior cohort studies identified a high risk subgroup comprised of variation in COMT genotype and pain catastrophizing. This subgroup had increased chance of heightened pain responses (in a pre-clinical model) and higher 12month post-operatives pain intensity ratings (in a clinical model). This pre-clinical trial will test mechanisms and efficacy of personalized pain interventions matched to the genetic and psychological characteristics of the high-risk subgroup.

METHODS

Potential participants will be screened for high risk subgroup membership, appropriateness for exercise-induced muscle injury protocol, and appropriateness for propranolol administration. Eligible participants that consent to the study will then be randomized into one of four treatment groups; 1) personalized pharmaceutical and psychological education; 2) personalized pharmaceutical and general education; 3) placebo pharmaceutical and psychological education; 4) placebo pharmaceutical and psychological education. Over the 5-day study period participants will complete an exercise-induced muscle injury protocol and receive study interventions. Pain and disability assessments will be completed daily, with primary outcomes being duration of shoulder pain (number of days until recovery), peak shoulder pain intensity, and peak shoulder disability. Secondary outcomes include inflammatory markers, psychological mediators, and measures of pain sensitivity regulation.

CONCLUSION

This pre-clinical trial builds on prior cohort studies and its completion will provide foundational data supporting efficacy and mechanisms of personalized interventions for individuals that may be at increased risk for developing chronic shoulder pain.

TRIAL REGISTRATION

ClinicalTrials.gov registry, NCT02620579 (Registered on November 13, 2015).

Fibromyalgia: A Critical and Comprehensive Review

Fibromyalgia is a disorder that is part of a spectrum of syndromes that lack precise classification. It is often considered as part of the global overview of functional somatic syndromes that are otherwise medically unexplained or part of a somatization disorder. Patients with fibromyalgia share symptoms with other functional somatic problems, including issues of myalgias, arthralgias, fatigue and sleep disturbances. Indeed, there is often diagnostic and classification overlap for the case definitions of a variety of somatization disorders. Fibromyalgia, however, is a critically important syndrome for physicians and scientists to be aware of. Patients should be taken very seriously and provided optimal care. Although inflammatory, infectious, and autoimmune disorders have all been ascribed to be etiological events in the development of fibromyalgia, there is very little data to support such a thesis. Many of these disorders are associated with depression and anxiety and may even be part of what has been sometimes called affected spectrum disorders. There is no evidence that physical trauma, i.e., automobile accidents, is associated with the development or exacerbation of fibromyalgia. Treatment should be placed on education, patient support, physical therapy, nutrition, and exercise, including the use of drugs that are approved for the treatment of fibromyalgia. Treatment should not include opiates and patients should not become poly pharmacies in which the treatment itself can lead to significant morbidities. Patients with fibromyalgia are living and not dying of this disorder and positive outlooks and family support are key elements in the management of patients.

TMD and chronic pain: a current view

This review aims at presenting a current view on the physiopathologic mechanisms associated with temporomandibular disorders (TMDs). While joint pain is characterized by a well-defined inflammatory process mediated by tumor necrosis factor-α and interleukin, chronic muscle pain presents with enigmatic physiopathologic mechanisms, being considered a functional pain syndrome similar to fibromyalgia, irritable bowel syndrome, interstitial cystitis and chronic fatigue syndrome. Central sensitization is the common factor unifying these conditions, and may be influenced by the autonomic nervous system and genetic polymorphisms. Thus, TMDs symptoms should be understood as a complex response which might get worse or improve depending on an individual's adaptation.

Multivariate morphological brain signatures predict patients with chronic abdominal pain from healthy control subjects

Irritable bowel syndrome (IBS) is the most common chronic visceral pain disorder. The pathophysiology of IBS is incompletely understood; however, evidence strongly suggests dysregulation of the brain-gut axis. The aim of this study was to apply multivariate pattern analysis to identify an IBS-related morphometric brain signature that could serve as a central biological marker and provide new mechanistic insights into the pathophysiology of IBS. Parcellation of 165 cortical and subcortical regions was performed using FreeSurfer and the Destrieux and Harvard-Oxford atlases. Volume, mean curvature, surface area, and cortical thickness were calculated for each region. Sparse partial least squares discriminant analysis was applied to develop a diagnostic model using a training set of 160 females (80 healthy controls and 80 patients with IBS). Predictive accuracy was assessed in an age-matched holdout test set of 52 females (26 healthy controls and 26 patients with IBS). A 2-component classification algorithm comprising the morphometry of (1) primary somatosensory and motor regions and (2) multimodal network regions explained 36% of the variance. Overall predictive accuracy of the classification algorithm was 70%. Small effect size associations were observed between the somatosensory and motor signature and nongastrointestinal somatic symptoms. The findings demonstrate that the predictive accuracy of a classification algorithm based solely on regional brain morphometry is not sufficient, but they do provide support for the utility of multivariate pattern analysis for identifying meaningful neurobiological markers in IBS.

AG. Persistent Catechol-O-methyltransferase-dependent Pain Is Initiated by Peripheral β-Adrenergic Receptors

BACKGROUND

Patients with chronic pain disorders exhibit increased levels of catecholamines alongside diminished activity of catechol-O-methyltransferase (COMT), an enzyme that metabolizes catecholamines. The authors found that acute pharmacologic inhibition of COMT in rodents produces hypersensitivity to mechanical and thermal stimuli via β-adrenergic receptor (βAR) activation. The contribution of distinct βAR populations to the development of persistent pain linked to abnormalities in catecholamine signaling requires further investigation.

METHODS

Here, the authors sought to determine the contribution of peripheral, spinal, and supraspinal βARs to persistent COMT-dependent pain. They implanted osmotic pumps to deliver the COMT inhibitor OR486 (Tocris, USA) for 2 weeks. Behavioral responses to mechanical and thermal stimuli were evaluated before and every other day after pump implantation. The site of action was evaluated in adrenalectomized rats receiving sustained OR486 or in intact rats receiving sustained βAR antagonists peripherally, spinally, or supraspinally alongside OR486.

RESULTS

The authors found that male (N = 6) and female (N = 6) rats receiving sustained OR486 exhibited decreased paw withdrawal thresholds (control 5.74 ± 0.24 vs. OR486 1.54 ± 0.08, mean ± SEM) and increased paw withdrawal frequency to mechanical stimuli (control 4.80 ± 0.22 vs. OR486 8.10 ± 0.13) and decreased paw withdrawal latency to thermal heat (control 9.69 ± 0.23 vs. OR486 5.91 ± 0.11). In contrast, adrenalectomized rats (N = 12) failed to develop OR486-induced hypersensitivity. Furthermore, peripheral (N = 9), but not spinal (N = 4) or supraspinal (N = 4), administration of the nonselective βAR antagonist propranolol, the β2AR antagonist ICI-118,511, or the β3AR antagonist SR59230A blocked the development of OR486-induced hypersensitivity.

CONCLUSIONS

Peripheral adrenergic input is necessary for the development of persistent COMT-dependent pain, and peripherally-acting βAR antagonists may benefit chronic pain patients.

Recent Advancements in Temporomandibular Disorders (TMDs)

TMDs are a group of conditions affecting the joint and or the muscles of mastication.TMDs consist of three main groups of conditions: myofascial pain; disc disorders; TMJ arthritides.The gold standard diagnostic criteria for research involving TMDs are the Research Diagnostic Criteria for TMDs (RDC/TMD). A pragmatic clinically applicable alternative is the Clinical examination protocol for TMDs (CEP-TMD).Signs and symptoms can include: pain in masticatory musculature and or the joint; noises associated with joint movements; locking; headache; otalgia.TMDs' aetiology is multifactorial and biopsychosocial in nature.Reversible conservative management as defined by the American Association of Dental Research is the initial management of choice for all subgroups of TMDs.

Differences in the Antinociceptive Effects and Binding Properties of Propranolol and Bupranolol Enantiomers

Recent efforts have suggested that the β-adrenergic receptor (β-AR) system may be a novel and viable therapeutic target for pain reduction; however, most of the work to date has focused on the β(2)-adrenergic receptor (AR). Here, we compared the antinociceptive effects of enantiomeric configurations of propranolol and bupranolol, two structurally similar nonselective β-blocking drugs, against mouse models of inflammatory and chronic pain. In addition, we calculated in silico docking and measured the binding properties of propranolol and bupranolol for all 3 β-ARs. Of the agents examined, S-bupranolol is superior in terms of its antinociceptive effect and exhibited fewer side effects than propranolol or its associated enantiomers. In contrast to propranolol, S-bupranolol exhibited negligible β-AR intrinsic agonist activity and displayed a full competitive antagonist profile at β(1)/β(2)/β(3)-ARs, producing a unique blockade of β(3)-ARs. We have shown that S-bupranolol is an effective antinociceptive agent in mice without negative side effects. The distinctive profile of S-bupranolol is most likely mediated by its negligible β-AR intrinsic agonist activity and unique blockade of β(3)-AR. These findings suggest that S-bupranolol instead of propranolol may represent a new and effective treatment for a variety of painful conditions.

PERSPECTIVE

The S enantiomer of bupranolol, a β-receptor antagonist, shows greater antinociceptive efficacy and a superior preclinical safety profile and it should be considered as a unique β-adrenergic receptor compound to advance future clinical pain studies.