Ovarian hormones and pain response: A review of clinical and basic science studies

Activation of GABAergic neurons in the dorsal raphe nucleus alleviates hyperalgesia induced by ovarian hormone withdrawal

ABSTRACT

Menopausal and postmenopausal women, characterized by a significant reduction in ovarian hormones, have a high prevalence of chronic pain with great pain intensity. However, the underlying mechanism of hyperalgesia induced by ovarian hormone withdrawal remains poorly understood. Here, we report that decreases in the activity and excitability of GABAergic neurons in the dorsal raphe nucleus (DRN) are associated with hyperalgesia induced by ovariectomy in mice. Supplementation with 17β-estradiol, but not progesterone, is sufficient to increase the mechanical pain threshold in ovariectomized (OVX) mice and the excitability of DRN GABAergic (DRN GABA ) neurons. Moreover, activation of the DRN GABA neurons projecting to the lateral parabrachial nucleus was critical for alleviating hyperalgesia in OVX mice. These findings show the essential role of DRN GABA neurons and their modulation by estrogen in regulating hyperalgesia induced by ovarian hormone withdrawal, providing therapeutic basis for the treatment of chronic pain in physiological or surgical menopausal women.

Early menopause is associated with higher disease activity independent of inflammation in postmenopausal-onset rheumatoid arthritis

OBJECTIVE

Early menopause (EM, age ≤ 45 years) is associated with an increased risk of developing rheumatoid arthritis (RA). We aimed to investigate its impact on disease characteristics in RA patients.

METHODS

This cross-sectional study included natural post-menopausal RA patients from an observational RA cohort recruited between January 2015 and October 2023. Demographic characteristics and clinical data were collected. Patients were divided into EM and usual menopause (UM, menopause age > 45 years) groups. Patients-reported outcomes (PROs, included patient global assessment of disease activity [PtGA], pain visual analogue scale [VAS] and Stanford health assessment questionnaire disability index [HAQ-DI]), and PROs-associated indicators (included 28-joint tender joint count [TJC28] and provider global assessment of disease activity [PrGA]) were assessed.

RESULTS

Among 1427 female RA patients, 557 natural post-menopausal RA patients were enrolled. The peak menopause age was between 46 and 50 years, with RA incidence peaking 5 years post-menopause. Compared with UM patients, RA patients with natural EM (n = 98,17.6%) exhibited more serious disease, including worse PROs and PROs-associated indicators, as well as higher C-reactive protein (CRP, all P < 0.05). Among 344 (61.8%) patients with RA onset after menopause, EM patients (n = 62, 18.0%) were characterized with worse PROs and PROs-associated indicators than those with UM patients (all P < 0.05), but no difference in inflammatory makers. Multivariate linear regression showed that menopause age was independently and negatively associated with PROs, including PtGA (β = -0.872, 95% CI -1.619, -0.125), HAQ-DI (β = -0.646, 95% CI -1.059, -0.233) in RA patients especially in those onset after menopause (PtGA [β = -1.028, 95% CI -2.022, -0.034]; HAQ-DI [β = -0.916, 95% CI -1.461, -0.370]).

CONCLUSION

Early menopause impacts on PROs independent of inflammation in patients with RA especially in those with postmenopausal-onset RA, which imply the importance of differentiation of non-inflammatory disease activity.

Yoga for Psychophysiological Wellbeing during Menstrual Phases in Eumenorrheic Females

Hormonal shifts during the menstrual cycle (MC) cause autonomic imbalances and psycho-physiological distress in eumenorrheic females. This present study reveals that yoga proactively improves the overall psychophysiological health and wellness in eumenorrheic female college students during different phases of MC. Healthy eumenorrheic female college students (Mage= 20.11 ± 5.39 years, n = 82) were randomized to a control and yoga group (n = 41). A well-conceptualized yoga module (CYM) for 5 days/week for 3 months (1 h daily in the morning) was practiced by the yoga group volunteers. Intra and intergroup comparisons were performed for the estimation of mindfulness awareness scale (MAAS), menstrual distress questionnaire (MDQ), cardiometabolic risk factors, heart rate variability (HRV), and endurance fitness during the luteal (LP) and follicular (FP) phases. Psychophysiological discomforts before CYM practice were mostly observed during LP compared to FP due to significant changes in mindfulness, pain, concentration, autonomic reactivity, negative affect, double product (DoP), rate pressure product (RPP), and HRV values. CYM practice influenced HRV parameters for an increase in parasympathetic activity and a decrease in sympathetic balance for better cardiac-autonomic functioning, with significant improvement in maximal oxygen consumption (VO2max) and physical work capacity (PWC170). Accordingly, MAAS and MDQ scores also improved significantly after yogic practice. The intra-group and inter-group significant improvements in psychophysiological parameters through CYM practice are relevant in eumenorrheic females to perform effectively throughout their MC period, by improving MC distress and sympathovagal (LF/HF) balance.

Effect of early follicular phase of menstrual cycle on hip flexion-extension isokinetic parameters in sedentary female students

Researchers conducted this observational study on sixty young females to detect the effect of the early follicular phase of the menstrual cycle on hip muscle performance. The Biodex Isokinetic dynamometer 4 pro was used. The authors used a dependent t-test and detected a statistically significant increase in the mean values of all hip flexion and extension isokinetic parameters at angular velocities 90°/sec and 180°/sec (p < 0.05) post-menstruation in comparison to the early follicular phase. The AGON/ANTAG ratio and hip ROM had a statistically significant reduction at the angular velocity 90°/sec (p = 0.003, p = 0.041 respectively) post-menstruation in comparison to the early follicular phase, while they showed no statistically significant change at the angular velocity 180°/sec (p = 0.070, p = 0.236 respectively). The authors through these results try to direct physiotherapists and physical education instructors to schedule training and activities for sedentary females according to their menstrual cycles to avoid any risk of injury.

Discriminating fingerprints of chronic neuropathic pain following spinal cord injury using artificial neural networks and mass spectrometry analysis of female mice serum

Spinal cord injury (SCI) often leads to central neuropathic pain, a condition associated with significant morbidity and is challenging in terms of the clinical management. Despite extensive efforts, identifying effective biomarkers for neuropathic pain remains elusive. Here we propose a novel approach combining matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) with artificial neural networks (ANNs) to discriminate between mass spectral profiles associated with chronic neuropathic pain induced by SCI in female mice. Functional evaluations revealed persistent chronic neuropathic pain following mild SCI as well as minor locomotor disruptions, confirming the value of collecting serum samples. Mass spectra analysis revealed distinct profiles between chronic SCI and sham controls. On applying ANNs, 100% success was achieved in distinguishing between the two groups through the intensities of m/z peaks. Additionally, the ANNs also successfully discriminated between chronic and acute SCI phases. When reflexive pain response data was integrated with mass spectra, there was no improvement in the classification. These findings offer insights into neuropathic pain pathophysiology and underscore the potential of MALDI-TOF MS coupled with ANNs as a diagnostic tool for chronic neuropathic pain, potentially guiding attempts to discover biomarkers and develop treatments.

Identifying microRNAs Possibly Implicated in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome and Fibromyalgia: A Review

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) and fibromyalgia (FM) are chronic syndromes of unknown etiology, accompanied by numerous symptoms affecting neurological and physical conditions. Despite frequent revisions of the diagnostic criteria, clinical practice guidelines are often outdated, leading to underdiagnosis and ineffective treatment. Our aim was to identify microRNA (miRNA) biomarkers implicated in pathological mechanisms underlying these diseases. A comprehensive literature review using publicly accessible databases was conducted. Interesting miRNAs were extracted from relevant publications on ME/CFS and/or FM, and were then linked to pathophysiological processes possibly manifesting these chronic diseases. Dysregulated miRNAs in ME/CFS and FM may serve as promising biomarkers for these diseases. Key identified miRNAs, such as miR-29c, miR-99b, miR-128, miR-374b, and miR-766, were frequently mentioned for their roles in immune response, mitochondrial dysfunction, oxidative stress, and central sensitization, while miR-23a, miR-103, miR-152, and miR-320 were implicated in multiple crucial pathological processes for FM and/or ME/CFS. In summary, both ME/CFS and FM seem to share many dysregulated biological or molecular processes, which may contribute to their commonly shared symptoms. This miRNA-based approach offers new angles for discovering molecular markers urgently needed for early diagnosis or therapeutics to tackle the pathology of these medically unexplained chronic diseases.

[Migraine and pregnancy : Gender-specific aspects and current knowledge]

BACKGROUND

Migraine, a frequent and debilitating neurological disease, shows gender-specific differences in prevalence and severity. Pregnancy is associated with numerous unique features in terms of migraine course, treatment options and differential diagnoses.

OBJECTIVES

How does pregnancy influence the course of migraine? What are the possible treatment options during pregnancy? Which differential diagnoses should be considered?

MATERIAL AND METHODS

Narrative review with summary and discussion of relevant studies and guidelines on migraine in pregnancy.

RESULTS

During pregnancy up to three quarters of women experience improvement of their migraine; however, there may be a renewed increase in frequency after childbirth. Choosing an appropriate treatment during pregnancy requires a careful risk-benefit assessment. It is important to consider secondary causes of headache as these can occur more frequently during pregnancy and some can be life-threatening.

CONCLUSION

Consideration of specific aspects of migraine in pregnancy is crucial to be able to develop the best possible treatment strategies for affected patients.

Progesterone Receptor Activation Regulates Sensory Sensitivity and Migraine Susceptibility

Women develop chronic pain during their reproductive years more often than men, and estrogen and progesterone regulate this susceptibility. We tested whether brain progesterone receptor (PR) signaling regulates pain susceptibility. During the estrous cycle, animals were more sensitive to mechanical stimulus during the estrus stage than in the diestrus stage, suggesting a role for reproductive hormones, estrogen, and progesterone. Progesterone treatment of ovariectomized and estrogen-primed mice caused a delayed reduction in the mechanical threshold. Segesterone, a specific agonist of PRs replicated this effect, whereas, the segesterone-induced reduction in mechanical threshold was blocked in the mice lacking PRs in the nervous system. Segesterone treatment also did not alter mechanical threshold in adult male and juvenile female mice. PR activation increased the cold sensitivity but did not affect the heat and light sensitivity. We evaluated whether PR activation altered experimental migraine. Segesterone and nitroglycerin when administered sequentially, reduced the pain threshold but not when given separately. PRs were expressed in several components of the migraine ascending pain pathway, and their deletion blocked the painful effects of nitroglycerin. PR activation also increased the number of active neurons in the components of the migraine ascending pain pathway. These studies have uncovered a pain-regulating function of PRs. Targeting PRs may provide a novel therapeutic avenue to treat chronic pain and migraine in women. PERSPECTIVE: This article provides evidence for the role of progesterone receptors in regulating pain sensitivity and migraine susceptibility in females. Progesterone receptors may be a therapeutic target to treat chronic pain conditions more prevalent in women than men.

Psoriatic Arthritis Involving TMJ: A Review on Pathogenesis and Consideration on Eventual Gender Differences

Psoriatic arthritis is defined as chronic inflammatory arthritis associated with psoriasis. The current data regarding gender differences in clinical manifestation and therapeutic outcomes of psoriatic arthritis are limited. Generally, men show a peripheral disease manifestation, while women have an axial distribution of the lesions. If we look at temporomandibular joint (TMJ) involvement, epidemiological data on the involvement of the TMJ are hard to find. Few studies on therapeutic management and the related impact on the quality of life are reported in the literature. Given the morpho-functional peculiarities of the TMJ and the different pain burdens between male and female genders, when manifestation of psoriatic arthritis occurs, clinicians should face it using a multidisciplinary approach for a correct diagnosis and successful treatment. This review aims to examine the diagnostic signs of psoriatic arthritis in the TMJ, the eventual variations of this disease in male and female patients, and the therapeutical strategies. The coordination of different specialties is fundamental to the remission of clinical symptoms and lesion regression.

Higher rating of perceived exertion and lower perceived recovery following a graded exercise test during menses compared to non-bleeding days in untrained females

The underrepresentation of the female population in exercise sciences could be attributed, at least in part, to difficulty in appropriately accounting for the effects of the menstrual cycle (MC). Previous studies examining the effects of the MC on aerobic performance and subjective measures of aerobic performance show conflicting results. Purpose: The study examined how the MC affects the objective and subjective measures of aerobic performance within untrained female participants and in comparison with untrained male participants assessed at similar time intervals. Methods: Twenty-one participants (12 females and 9 males) completed a graded exercise test (GXT) on a cycle ergometer. The female participants were tested during their early follicular (EF; menses), ovulatory (O), and mid-luteal (ML) phases of the MC. The male participants were included as the control group and were randomly assigned to a menstrual cycle phase for each visit. During GXT, maximal oxygen consumption (VO2max), respiratory exchange ratio (RER), maximal heart rate (HRmax), peak blood lactate, and rating of perceived exertion (RPE) were determined. Twenty-four hours post-exercise, the perceived recovery status (PRS) was assessed. The MC phase was estimated using basal body temperature (BBT) in the female participants. Results: The male participants obtained a higher peak power and VO2max compared to the female participants (p < 0.05). All objective measures of aerobic performance did not significantly differ across the MC phases or time points that were tested. In the untrained female participants, an effect of the MC phase on RPE was found, with RPE being higher at EF (8.92 ± 0.79) compared to O (7.67 ± 1.23; p < 0.05) and ML (7.75 ± 1.06; p < 0.05). In addition, an effect of the MC phase on PRS was found, with perceived recovery being lower at EF (6.83 ± 0.94) compared to O (8.83 ± 1.12) and ML (8.67 ± 0.65; all p < 0.005) for the untrained female participants. No significant differences in RPE and PRS were found between tests in the untrained male participants. The female participants had lower perceived recovery following EF (6.83 ± 0.94) compared with the male participants (9.00 ± 1.00; p < 0.001). Conclusion: The untrained female participants perceived greater exertion during GXT and impaired recovery following GXT in EF compared to O and ML. These results may be attributed to either a drop in female sex hormone concentrations or discomfort associated with menses. The male participants did not exhibit any changes over time. Future studies using subjective parameters such as perceived exertion to track the internal load of training in the naturally menstruating female population should consider menses.

Menstrual migraine is caused by estrogen withdrawal: revisiting the evidence

OBJECTIVE

To explore and critically appraise the evidence supporting the role of estrogen withdrawal in menstrual migraine.

MAIN BODY

Menstrual migraine, impacting about 6% of reproductive-age women, manifests as migraine attacks closely related to the menstrual cycle. The estrogen withdrawal hypothesis posits that the premenstrual drop in estrogen levels serves as a trigger of migraine attacks. Despite its wide acceptance, the current body of evidence supporting this hypothesis remains limited, warranting further validation. Estrogen is believed to exert a modulatory effect on pain, particularly within the trigeminovascular system - the anatomic and physiologic substrate of migraine pathogenesis. Nevertheless, existing studies are limited by methodologic inconsistencies, small sample sizes, and variable case definitions, precluding definitive conclusions. To improve our understanding of menstrual migraine, future research should concentrate on untangling the intricate interplay between estrogen, the trigeminovascular system, and migraine itself. This necessitates the use of robust methods, larger sample sizes, and standardized case definitions to surmount the limitations encountered in previous investigations.

CONCLUSION

Further research is thus needed to ascertain the involvement of estrogen withdrawal in menstrual migraine and advance the development of effective management strategies to address unmet treatment needs.

Changes in sex hormones and their interactions are related to pain perception between different menstrual subphases

Whether sex hormones are related to pain perception across the menstrual cycle is unclear. We examined changes in experimental pain perception in healthy young females between the early to midfollicular subphase (emF) and the midluteal subphase (mL) and explored the role of sex hormones. Sixty-six participants were involved in the study. We tested pressure pain, cold pain, ischemic pain, and needle pain, while at the same time we measured sex hormones levels in two menstrual subphases. Only the right ulna pressure test showed a significant reduction in pain threshold (PPTh3) during the mL. The absolute change of PPTh3 (PPTh3mL - PPTh3emF) was related to the absolute change of prolactin. The relative change of the range of pain tolerance for pressure pain of the right ulna (RPT3rc) was related to the relative change of progesterone (Prc) and estradiol (E2rc) levels, and the interaction effects showed that at Prc ≤ 30, E2rc was positively correlated with RPT3rc. The same, the relative change of pressure pain tolerance of the pulp of the middle finger on the right hand (PPTo4rc) was related to E2rc and Prc, and the results of the interaction between E2rc and Prc suggest that when E2rc is ≤0.8, Prc is positively correlated with PPTo4rc. Two different formulas were applied in this study and showed inconsistent results. Most pain tests showed no difference between the two subphases of the menstrual cycle. Only the relative changes of the PPTo4 and RPT3 are related to the E2rc and Prc, respectively, between menstrual subphases in an interactive way in healthy young women.

Progesterone receptor activation regulates sensory sensitivity

Women develop chronic pain during their reproductive years more often than men, and estrogen and progesterone regulate this susceptibility. We tested whether brain progesterone receptor (PR) signaling regulates pain susceptibility. During the estrous cycle, animals were more sensitive to pain during the estrus stage than in the diestrus stage, suggesting a role for reproductive hormones, estrogen, and progesterone. We measured the pain threshold daily for four days in ovariectomized, estrogen-primed animals treated with progesterone. The pain threshold was lower 2 days later and stayed that way for the duration of the testing. A specific progesterone-receptor (PR) agonist, segesterone, promoted pain, and mice lacking PR in the brain (PRKO) did not experience lowered pain threshold when treated with progesterone or segesterone. PR activation increased the cold sensitivity but did not affect the heat sensitivity and had a small effect on light sensitivity. Finally, we evaluated whether PR activation altered experimental migraine. Segesterone and nitroglycerin (NTG) when administered sequentially, reduced pain threshold but not separately. These studies have uncovered a pain-regulating function of PRs. Targeting PRs may provide a novel therapeutic avenue to treat chronic pain in women.

Sex and age differences in chronic postoperative pain among patients undergoing thoracic surgery: a retrospective cohort study

Background

The effect of sex and age on chronic post-thoracic surgical pain (CPTP) at rest and with activity remains unclear. The main purpose of this study was to investigate the relationship between the incidence of chronic postoperative pain (at rest and with activity) and sex/age differences.

Methods

This was a single-center retrospective study that included adult patients who had undergone elective thoracic surgery. Patients were divided into two groups based on sex. Demographic and perioperative data were collected, including age, sex, education level, Body Mass Index (BMI), American Society of Anesthesiologists (ASA) physical status, and medical history (hypertension, diabetes mellitus). Chronic postoperative pain data were collected by telephone follow-up.

Results

Among the 3,159 patients enrolled, 1,762 were male, and 1,397 were female. After creating a matched-pairs cohort, 1,856 patients were analyzed. The incidence of CPTP at rest was 14.9% among males and 17.8% among females (p = 0.090). The incidence of CPTP with activity was 28.4% among males and 35.0% among females (p = 0.002). We analyzed three different models after propensity matching to validate the stability of the prediction model between sex and CPTP, and female sex was a significant predictor of CPTP with activity 3 months after surgery. Further analysis showed that females in the 45-55-year-old age group were more prone to develop CPTP.

Conclusion

Females have a higher incidence of chronic postoperative pain with activity after thoracic surgery. Females in the 45-55-year-old age group are more prone to develop CPTP than females in other age groups.

Headache-a challenge across medical students' life: a systematic review and meta-analysis

BACKGROUND

Headache is a disabling disease that affects psychosocial factors. Medical students are recognized to be more susceptible to psychological stress than other. Quantitative summaries of prevalence studies on this subject are limited. The aim of this study was to quantify and comprehend the variance in prevalence at the global and regional levels.

METHODS

We used a comprehensive search approach to find studies on headaches prevalence in the medical literature published between November 1990 and May 5, 2022. Database searched were PubMed, Scopus, EMBASE, and Google Scholar. Studies that reported headaches (unspecified, migraine, or tension-type headache (TTH)) in medical students were included. Subgroup analysis and meta-regression were applied to investigate heterogeneity, with the risk of bias tool employed to assess study quality. PROSPERO number CRD42022321556 was assigned to the study protocol.

RESULTS

Out of 1561 studies, 79 were included. The pooled prevalence estimates of unspecified headache, migraine, and TTH were 70.44% (95% CI: 63.32-77.57), 18.9% (95% CI: 15.7-22.0), and 39.53% (95% CI: 31.17-47.90), respectively. TTH and migraine were more prevalent in Eastern Mediterranean and American region. TTH and migraine were less prevalent in higher income countries.

CONCLUSION

Although the prevalence of headaches among medical students varies in different countries, it is higher than the general population of the same age. Higher stressors and overwork in these students may contribute to this condition. The well-being of medical students should be a priority for the relevant authorities.

Migraine and the Gender Divide

Migraine is a global neurologic disease that is highly prevalent, especially in women. Studies have observed a predisposition for the development of migraine in women, although the mechanisms involved have yet to be fully elucidated. This review aimed to summarize the recent evidence regarding the epidemiology, pathophysiology, and treatment of migraine and highlight key sex differences. We also identify gaps in care for both women and men living with migraine and discuss the presence of migraine-related stigma and how this may impact the efficacy of clinical care.

Prevalence of temporomandibular disorders in children and adolescents evaluated with Diagnostic Criteria for Temporomandibular Disorders: A systematic review with meta-analysis

BACKGROUND

The prevalence of temporomandibular disorders (TMDs) in children and adolescents is not well-known. This is partly because TMD is not often diagnosed in children and partly because there is no agreed-upon definition of TMD. There is a growing body of evidence to suggest that there are gender differences in the prevalence and presentation of TMD in adult. The aim was to assess the prevalence of TMDs in subjects aged 8-19 evaluated with Diagnostic Criteria for TMDs (DC/TMD) and to assess gender differences.

METHODS

PubMed, Web of Science and Lilacs were systematically searched until 30 November 2022, to identify studies presenting children and adolescents patients affected by TMDs.

RESULTS

Out of 40 papers, three studies were included. The included subjects in this review were 1914 (1093 female and 821 male). Seven hundred and thirty-six on 1914 patients (38.4%) presented TMD. Among 1093 female, 489 (44.7%) presented TMD, while 247/821 male (30%) experienced TMD. Meta-analysis revealed that the female had a higher TMD prevalence than male (RR 2.10; 95% CI: 1.21-3.65).

CONCLUSION

TMD prevalence in children and adolescence varies between 20% and 60%. Female had a higher prevalence of TMDs compared to male.

The genetic basis of endometriosis and comorbidity with other pain and inflammatory conditions

Endometriosis is a common condition associated with debilitating pelvic pain and infertility. A genome-wide association study meta-analysis, including 60,674 cases and 701,926 controls of European and East Asian descent, identified 42 genome-wide significant loci comprising 49 distinct association signals. Effect sizes were largest for stage 3/4 disease, driven by ovarian endometriosis. Identified signals explained up to 5.01% of disease variance and regulated expression or methylation of genes in endometrium and blood, many of which were associated with pain perception/maintenance (SRP14/BMF, GDAP1, MLLT10, BSN and NGF). We observed significant genetic correlations between endometriosis and 11 pain conditions, including migraine, back and multisite chronic pain (MCP), as well as inflammatory conditions, including asthma and osteoarthritis. Multitrait genetic analyses identified substantial sharing of variants associated with endometriosis and MCP/migraine. Targeted investigations of genetically regulated mechanisms shared between endometriosis and other pain conditions are needed to aid the development of new treatments and facilitate early symptomatic intervention.

Alterations in regional homogeneity and multiple frequency amplitudes of low-frequency fluctuation in patients with new daily persistent headache: a resting-state functional magnetic resonance imaging study

BACKGROUND

New daily persistent headache (NPDH) is a rare primary headache that is highly disabling. The pathophysiology of NDPH is still unclear, and we aimed to reveal the underlying mechanism of NDPH through functional magnetic resonance imaging (fMRI) analysis.

METHODS

In this cross-sectional study, thirty patients with NDPH and 30 healthy controls (HCs) were recruited. The blood oxygen level-dependent (BOLD) sequences of all participants were obtained using the GE 3.0 T system. We performed ReHo, ALFF (conventional band: 0.01-0.08 Hz, slow-5: 0.01-0.027 Hz, slow-4: 0.027-0.073 Hz) and seed-based to the whole brain functional connectivity (FC) analysis in the NDPH and HC groups. The sex difference analysis of ReHo, ALFF, and FC values was conducted in the NDPH group. We also conducted Pearson's correlation analysis between ReHo, ALFF, FC values and clinical characteristics (pain intensity, disease duration, HIT-6, GAD-7, PHQ-9, and PSQI scores).

RESULTS

Both increased ReHo (P_FWE-corr = 0.012) and ALFF values (0.01-0.08 Hz, P_FWE-corr = 0.009; 0.027-0.073 Hz, P_FWE-corr =0.044) of the left middle occipital gyrus (MOG_L) were found in the NDPH group compared to the HC group. There was no significant difference in FC maps between the two groups. Compared to the HC group, no difference was found in ReHo (p = 0.284), ALFF (p = 0.246), and FC (p = 0.118) z scores of the MOG_L in the NDPH group. There was also no sex difference in ReHo (p = 0.288), ALFF (p = 0.859), or FC z score (p = 0.118) of the MOG_L in patients with NDPH. There was no correlation between ReHo, ALFF, FC z scores and clinical characteristics after Bonferroni correction (p < 0.05/18).

CONCLUSIONS

Patients with NDPH may have abnormal activation of the visual system. Abnormal visual activation may occur mainly in higher frequency band of the classical band. No sex differences in brain activity were found in patients with NDPH.

Impact of early age at menopause on disease outcomes in postmenopausal women with rheumatoid arthritis: a large observational cohort study of Korean patients with rheumatoid arthritis

OBJECTIVES

To assess the differences in clinical outcomes between patients with rheumatoid arthritis (RA) with early menopause (EM) (<45 years) and usual menopause (UM) (≥45 years) and to identify the impact of EM on longitudinal changes in RA activity and patient-reported outcomes (PROs).

METHODS

We recruited 2878 postmenopausal women with RA from the Korean Observational Study Network for Arthritis. Patients were examined at baseline and for 5 consecutive years using the Simplified Disease Activity Index (SDAI), Health Assessment Questionnaire-Disability Index (HAQ-DI) and other PROs. Generalised estimating equation (GEE) analyses were performed among patients with a baseline SDAI of >11 to evaluate the impact of EM on longitudinal changes in RA activity and PROs.

RESULTS

The EM group (n=437) was younger than the UM group (n=2441), but the RA duration was similar between the two groups. The EM group was more educated and more likely to be seronegative at enrolment. Moreover, the EM group demonstrated higher disease activity and worse PROs for global assessment, fatigue, sleep disturbance and health-related quality of life (HRQoL) (all p<0.05) at baseline. The GEE model revealed that EM significantly influenced the rate of SDAI change (β=1.265, p=0.004) after adjusting for age, RA duration, biologics use and SDAI at baseline. The EM group was also significantly associated with increased HAQ-DI scores and decreased EQ-5D-utility values during the 5-year follow-up period.

CONCLUSION

Patients with RA and EM demonstrate higher disease activity and poorer HRQoL. Furthermore, EM significantly affects the longitudinal changes in disease activity and PROs in patients with RA.

Total tenderness score and pressure pain thresholds in persistent post-traumatic headache attributed to mild traumatic brain injury

Objective

To investigate whether persistent post-traumatic headache attributed to mild traumatic brain injury (TBI) is associated with more pronounced pericranial tenderness and lower pressure pain thresholds (PPTs) in the head and neck region, compared with healthy controls.

Methods

Patients with persistent post-traumatic headache (n = 100) and age- and gender-matched healthy controls (n = 100) were included between July 2018 and June 2019. Total tenderness score (TTS) was used to assess pericranial tenderness by bilateral manual palpation in eight muscles or tendon insertions. Summation was then used to calculate a TTS from 0 to 48 based on individual right- and left-sided scores; higher TTS score indicated more pronounced pericranial tenderness. PPTs were examined in m. temporalis and m. trapezius (upper and middle part) using an electronic pressure algometer that applies increasing blunt pressure at a constant rate.

Results

The TTS score was higher in patients with persistent post-traumatic headache (median, 21; IQR, 12–31), compared with healthy controls (median, 10; IQR, 6–17; P < .001). PPTs were lower in patients with persistent post-traumatic headache than in controls in both the left-sided m. temporalis (mean ± SD, 157.5 ± 59.9 vs. 201.1 ± 65.2; P < .001) and right-sided m. temporalis (mean ± SD, 159.5 ± 63.8 vs. 212.3 ± 61.9; P < .001). Furthermore, patients with persistent post-traumatic headache also had lower left- and right-sided PPTs in the upper as well as middle part of m. trapezius, compared with healthy controls; all P values were .05 or less.

Conclusions

Among patients with persistent post-traumatic headache, pericranial tenderness was more pronounced and PPTs in the head and neck region were lower than in healthy controls free of headache and mild TBI. Further research is needed to better understand the involvement of pericranial myofascial nociceptors in the disease mechanisms underlying post-traumatic headache.

Supplementary Information

The online version contains supplementary material available at 10.1186/s10194-022-01457-1.

Personal influencing factors for pressure pain threshold in healthy people: A systematic review and meta-analysis

All studies that investigated personal factors influencing pressure pain threshold (PPT) in healthy people were synthesized. Data was summarized, and risk of bias (RoB) and level of evidence were determined. Results were pooled per influencing factor, grouped by body region and included in meta-analyses. Fifty-four studies were eligible. Five had low, nine moderate, and 40 high RoB. Following meta-analyses, a strong conclusion was found for the influence of scapular position, a moderate for the influence of gender, and a weak for the influence of age (shoulder/arm region) and blood pressure on PPT. In addition, body mass index, gender (leg region), alcohol consumption and pain vigilance may not influence PPT. Based on qualitative summary, depression and menopause may not influence PPT. For other variables there was only preliminary or conflicting evidence. However, caution is advised, since the majority of included studies showed a high RoB and several were not eligible to include in meta-analyses. Heterogeneity was high in the performed meta-analyses, and most conclusions were weak. More standardized research is necessary.

The Menstrual Cycle Phase and Effect of Aromatherapy on Orthodontic Debonding Pain

Objectives: The aim of this prospective clinical study was to evaluate the effects of the menstrual cycle phases and aromatherapy on women's perception of orthodontic debonding pain. Materials and Methods: The materials of our study were consisted of randomly selected 48 female patients (mean age:19.00±3.40). Four different study groups were performed. LA+; the patients in the luteal phase and received aromatherapy(n=12), LA-; the patients in the luteal phase and did not receive aromatherapy(n=13), FA+; the patients in the follicular phase and received aromatherapy(n=11), FA-; the patients in the follicular phase and did not receive aromatherapy(n=12). Debonding was performed and the pain experience for each tooth was scored by the patient on a visual analogue scale (VAS). Also, participants' general responses to pain were assessed with the Pain Catastrophizing Scale (PCS). The aromatherapy protocol was to inhale lavender oil from approximately 30 cm for 3 minutes, 3 minutes before debonding. Results: It was found that the mean VAS scores were higher in the luteal phase than in the follicular phase, however this difference was not statistically significant. There was no statistically significant difference between the groups with and without aromatherapy in terms of VAS scores(P>0.05). The correlation between total PCS scores and total VAS scores was statistically significant (r=0.310, P

Estrogenic impregnation alters pain expression: analysis through functional neuropeptidomics in a surgical rat model of osteoarthritis

PURPOSE

Several observational studies suggest that estrogens could bias pain perception. To evaluate the influence of estrogenic impregnation on pain expression, a prospective, randomized, controlled, blinded study was conducted in a Sprague-Dawley rat model of surgically induced osteoarthritis (OA).

METHODS

Female rats were ovariectomized and pre-emptive 17β-estradiol (0.025 mg, 90-day release time) or placebo pellets were installed subcutaneously during the OVX procedures. Thirty-five days after, OA was surgically induced on both 17β-estradiol (OA-E) and placebo (OA-P) groups. Mechanical hypersensitivity was assessed by static weight-bearing (SWB) and paw withdrawal threshold (PWT) tests. Mass spectrometry coupled with high-performance liquid chromatography (HPLC-MS) was performed to quantify the spinal pronociceptive neuropeptides substance P (SP), calcitonin gene-related peptide (CGRP), bradykinin (BK), somatostatin (SST), and dynorphin-A (Dyn-A).

RESULTS

Compared to control, ovariectomized rats presented higher SP (P = 0.009) and CGRP (P = 0.017) concentrations. OA induction increased the spinal level of SP (+ 33%, P < 0.020) and decreased the release of BK (- 20%, (P < 0.037)). The OA-E rats at functional assessment put more % body weight on the affected hind limb than OA-P rats at D7 (P = 0.027) and D56 (P = 0.033), and showed higher PWT at D56 (P = 0.009), suggesting an analgesic and anti-allodynic effect of 17β-estradiol. Interestingly, the 17β-estradiol treatment counteracted the increase of spinal concentration of Dyn-A (P < 0.016) and CGRP (P < 0.018).

CONCLUSION

These results clearly indicate that 17β-estradiol interfers with the development of central sensitization and confirm that gender dimorphism should be considered when looking at pain evaluation.

Hypohydration but not Menstrual Phase Influences Pain Perception in Healthy Women

Chronic pain is a pervasive health problem and is associated with tremendous socioeconomic costs. However, current pain treatments are often ineffective due, in part, to the multi-factorial nature of pain. Mild hypohydration was shown to increase experimental pain sensitivity in men, but whether this also occurs in women has not been examined. Fluctuations in ovarian hormones (i.e., 17ß-oestradiol and progesterone) throughout the menstrual cycle may influence a woman's pain sensitivity, as well as hydration levels, suggesting possible interactions between hypohydration and menstrual phase on pain. We investigated the effects of mild hypohydration (HYPO, 24 hr of fluid restriction) on ischaemic pain sensitivity in 14 eumenorrheic women during the early follicular (EF) and mid-luteal (ML) phases of their menstrual cycle. We also examined whether acute water ingestion could reverse the negative effects of hypohydration. Elevated serum osmolality, plasma copeptin, and urine specific gravity indicated mild hypohydration. Compared to euhydration, HYPO reduced pain tolerance (by 34 ± 46 s; P = 0.02, ηp2 = 0.37) and increased ratings of pain intensity (by 0.7 ± 0.7 cm; P = 0.004; ηp2 = 0.55) and unpleasantness (by 0.7 ± 0.9 cm; P = 0.02; ηp2 = 0.40); these results were not influenced by menstrual phase. Water ingestion reduced thirst perception (Visual Analogue Scale, by 2.3 ± 0.9 cm; P < 0.001, ηp2 = 0.88) but did not reduce pain sensitivity. Therefore, hypohydration increases pain sensitivity in women with no influence of menstrual phase.

Potential differences in somatosensory function during premenopause and early and late postmenopause in patients with burning mouth syndrome: An observational case-control study

Background/purpose

Burning mouth syndrome (BMS) is a chronic condition presenting as intraoral burning or dysesthesia, with a high preponderance in menopausal women. This study aimed to examine the association between somatosensory dysfunction and BMS in premenopausal, early postmenopausal, and late postmenopausal patients, using a standardized Quantitative Sensory Testing (QST) protocol, and to determine the predictive value of thermal or mechanical perception by QST for detecting BMS.

Materials and methods

An observational case–control study was performed with 36 female participants with BMS (12 premenopausal, 10 early postmenopausal, and 14 late postmenopausal) and 42 age- and sex-matched healthy volunteers (21 premenopausal, 10 early postmenopausal, and 11 late postmenopausal). Neurophysiological tests were used to evaluate somatosensory dysfunction at the tongue.

Results

Z-score in the late postmenopausal BMS group revealed a gain of function for the cold pain threshold and heat pain threshold (Z = 2.08 and 3.38, respectively). In the multiple regression analysis with the Visual Analog Scale as the dependent variable, the vibration detection threshold predicted the severity of burning mouth sensation in the premenopausal group.

Conclusion

Late postmenopausal patients with BMS showed an increased response of the tongue to noxious thermal stimuli. This supports the theory that changes in sex hormones may affect trigeminal somatosensory function, particularly during the late postmenopausal stage in patients with BMS.

Differences in Postoperative Pain, Nausea, and Vomiting After Elective Laparoscopic Cholecystectomy in Premenopausal and Postmenopausal Mexican Women

BACKGROUND

Postoperative symptoms and pain after laparoscopic cholecystectomy (LC) are common in women. However, there is no evidence of differences in incidence and severity among different age groups. We evaluated whether adverse postoperative symptoms were more common in younger than in older women after LC.

METHODS

One hundred and fifty premenopausal (mean age 37.6 ± 3.6 y) and 145 postmenopausal women (59 ± 5.2 y) were included in this retrospective cohort study. Clinical and anthropometric parameters were analyzed. Study endpoints were the incidences of postoperative nausea and vomiting (PONV) and pain, and the additional analgesics and antiemetics needed after surgery.

RESULTS

Body mass index was normal in 42.7% of patients in the younger group and 64.8% in the older group (P < 0.001). Reported pain was more frequent and intense in the younger group throughout the study period (P < 0.01). Additional narcotics were required in 18% of premenopausal versus 7.6% of postmenopausal women (P = 0.001), and the doses used to reduce pain were higher for premenopausal women (P = 0.02). PONV was more frequent in the younger group at 1 and 6 h after surgery (P < 0.005). Rescue antiemetics were required in 29 premenopausal and 13 postmenopausal women (P = 0.01). Hospital stay was shorter for the older patients (P = 0.01). Minor morbidity was observed in both groups (0.7% and 2.1%). There was no mortality.

CONCLUSIONS

Early PONV and pain after LC were more frequent in premenopausal women, who also required more rescue analgesic and antiemetic medication.

Has the Phase of the Menstrual Cycle Been Considered in Studies Investigating Pressure Pain Sensitivity in Migraine and Tension-Type Headache: A Scoping Review

OBJECTIVE

The aim of this scoping review was to identify if the phase of the menstrual cycle was considered in observational studies comparing pressure pain sensitivity between women with migraine or tension-type headache (TTH) and headache-free women.

METHODS

A systematic electronic literature search in PubMed, Medline, Web of Science, Scopus, and CINAHL databases was conducted. Observational studies including one or more groups with TTH and/or migraine comparing pressure pain thresholds (PPTs) were included. The methodological quality (risk of bias) was assessed with the Newcastle-Ottawa Scale. Authors, objectives, inclusion/exclusion criteria, size sample, female sample, tool to assess PPTs, mean age, and the use of any medication were extracted and analyzed independently by two authors.

RESULTS

From a total of 1404 and 1832 identified articles for TTH and migraine, 30 and 18 studies satisfied the criteria and were included. Nineteen (63.4%) studies assessing TTH patients and eleven (61.1%) assessing migraine patients showed a high risk of bias. The most common flaws were attributed to improper selection of control and control over other additional factors. Based on the systematic review, just one study including TTH and one including migraine patients considered the menstrual cycle.

CONCLUSION

The results of this scoping review identified that the phase of the menstrual cycle has been rarely considered in studies investigating sensitivity to pressure pain in primary headaches, such as TTH or migraine, although there is evidence showing the relevance of the phase of the menstrual cycle in pain perception.

Hand Osteoarthritis: investigating Pain Effects of estrogen-containing therapy (HOPE-e): a protocol for a feasibility randomised placebo-controlled trial

BACKGROUND

Hand osteoarthritis (OA) is a common condition, causing pain, stiffness and reduced quality of life. Incidence is higher amongst women, particularly around the age of the menopause. Whilst the relationship between sex hormones and OA has been studied in vitro, in epidemiological studies and in clinical trials of hormone replacement therapy (HRT), this study is the first to investigate the effect of estrogen-containing therapy on hand pain in post-menopausal women with symptomatic hand OA in a randomised study design.

METHODS

This is a feasibility study of a double-blinded placebo-controlled intervention with 1:1 randomisation to either a combination of conjugated estrogens 0.45 mg and bazedoxifene acetate 20 mg (Duavive) or placebo. The target population is post-menopausal women with symptomatic hand OA, aiming to recruit 60-90 study participants. The primary objective is to assess the feasibility of a future fully powered randomised controlled trial (RCT). Participants will take the study medication for 24 weeks and be followed up for 28 weeks after randomisation. The primary outcomes used to determine feasibility are eligible participant identification rates and routes; recruitment, randomisation and retention rates of eligible participants; study medication compliance; and the likelihood of unintentional unblinding. Secondary outcomes include measures of hand pain, function, appearance and menopausal symptoms. An end of study questionnaire and focus groups will help to refine the final protocol for a full study.

DISCUSSION

Identifying new treatments for symptomatic hand OA is a recognised research priority. The study will help us to understand whether there are sufficient interested and eligible individuals in this target population who would consider HRT for their hand symptoms. It will provide proof-of-concept RCT data on the effects of HRT on hand pain and other clinically relevant outcomes in this population. The study will gain valuable information on the feasibility of a full RCT and how best to run this. The findings will be published in a peer-reviewed journal and presented at a relevant conference.

TRIAL REGISTRATION

ISRCTN12196200 registered on 15 January 2019.

An update on the management of chronic pelvic pain in women

Chronic pelvic pain represents a major public health problem for women and impacts significantly on their quality of life. Yet it is under-researched and a challenge to manage. Women who suffer from chronic pelvic pain frequently describe their healthcare journey as long, via a variety of specialists and frustrating, with their pain often dismissed. Aetiological factors and associations are best conceptualised using the 'three P's' model of predisposing, precipitating and perpetuating factors. This integrates the numerous biological, psychological and social contributors to the complex, multifactorial nature of chronic pelvic pain. Overall management involves analgesia, hormonal therapies, physiotherapy, psychological approaches and lifestyle advice, which like other chronic pain conditions relies on a multidisciplinary team approach delivered by professionals experienced and trained in managing chronic pelvic pain.

A Female Psoriatic Arthritis Patient Involving the TMJ

Psoriatic arthritis (PsA) is an inflammatory chronic arthritis associated with psoriasis. Currently, data about gender differences in clinical manifestation and therapeutic outcomes of PsA are limited. Frequently, women manifest a peripheral disease while men have an axial localization. Moreover, women display higher disease activity and physical activity limitations, if compared to men. Although the involvement of the temporomandibular joint (TMJ) is quite rare, it can seriously impact the quality of life. The morpho-functional peculiarities of TMJ require a multidisciplinary approach to perform a correct diagnosis and a successful treatment. Here, we report a case of a woman affected by PsA involving TMJ treated by combining pharmacological therapy and an occlusal splint. The coordination between different specialties led to a complete remission of clinical symptoms and a regression of lesions.

The effect of corrective and therapeutic exercises on bleeding volume and severe menstrual pain in non-athletic women

The aim of this study was to determine the relationship between lumbar lordosis and severe menstrual pain and bleeding for the improvement of the health status in women. This was a quasi-experimental study where the effects of a training program, (based on correctional and therapeutic exercises, on primary dysmenorrhoea and menstrual bleeding in women with hyper-lordosis) was determined. The severity of menstrual pain was evaluated by use of a questionnaire. There was a significant incidence of neurological pain, which was not reduced in the control group (who had no exercise). There was a significant relationship between the severity of menstrual pain and hyper-lordosis. In the intervention group, there was a significant decrease in the severity of menstrual pain following 12 weeks of exercise. Hyper-lordosis can be improved by performing corrective exercises and strengthening the abdominal muscles.Impact statementWhat is already known on this subject? Exercise is positively associated with changes in the menstrual cycle and has beneficial effects on menstruation.What do the results of this study add? This research determines the relationship between lumbar lordosis and severe menstrual pain and the association of severe menstrual bleeding, in order to take effective corrective actions to improve women's health.What are the implications of these findings for clinical practice and/or further research? Hyper-lordosis can be improved by corrective exercises and strengthening of the abdominal muscles.

Pain Across the Menstrual Cycle: Considerations of Hydration

Chronic pain – pain that persists for more than 3 months – is a global health problem and is associated with tremendous social and economic cost. Yet, current pain treatments are often ineffective, as pain is complex and influenced by numerous factors. Hypohydration was recently shown to increase ratings of pain in men, but studies in this area are limited (n = 3). Moreover, whether hypohydration also affects pain in women has not been examined. In women, changes in the concentrations of reproductive hormones across menstrual phases may affect pain, as well as the regulation of body water. This indicates potential interactions between the menstrual phase and hypohydration on pain, but this hypothesis has yet to be tested. This review examined the literature concerning the effects of the menstrual phase and hypohydration on pain, to explore how these factors may interact to influence pain. Future research investigating the combined effects of hypohydration and menstrual phase on pain is warranted, as the findings could have important implications for the treatment of pain in women, interpretation of previous research and the design of future studies.

Noxious pressure stimulation demonstrates robust, reliable estimates of brain activity and self-reported pain

Functional neuroimaging techniques have provided great insight in the field of pain. Utilising these techniques, we have characterised pain-induced responses in the brain and improved our understanding of key pain-related phenomena. Despite the utility of these methods, there remains a need to assess the test retest reliability of pain modulated blood-oxygen-level-dependant (BOLD) MR signal across repeated sessions. This is especially the case for more novel yet increasingly implemented stimulation modalities, such as noxious pressure, and it is acutely important for multi-session studies considering treatment efficacy. In the present investigation, BOLD signal responses were estimated for noxious-pressure stimulation in a group of healthy participants, across two separate sessions. Test retest reliability of functional magnetic resonance imaging (fMRI) data and self-reported visual analogue scale measures were determined by the intra-class correlation coefficient. High levels of reliability were observed in several key brain regions known to underpin the pain experience, including in the thalamus, insula, somatosensory cortices, and inferior frontal regions, alongside "excellent" reliability of self-reported pain measures. These data demonstrate that BOLD-fMRI derived signals are a valuable tool for quantifying noxious responses pertaining to pressure stimulation. We further recommend the implementation of pressure as a stimulation modality in experimental applications.

Differential Role of Anterior Cingulate Cortical Glutamatergic Neurons in Pain-Related Aversion Learning and Nociceptive Behaviors in Male and Female Rats

Pain is comprised of both sensory and affective components. The anterior cingulate cortex (ACC) is a key brain region involved in the emotional processing of pain. Specifically, glutamatergic transmission within the ACC has been shown to modulate pain-related aversion. In the present study, we use in vivo optogenetics to activate or silence, using channelrhodopsin (ChR2) and archaerhodopsin (ArchT) respectively, calmodulin-kinase IIα (CaMKIIα)-expressing excitatory glutamatergic neurons of the ACC during a formalin-induced conditioned place aversion (F-CPA) behavioral paradigm in both female and male adult Sprague-Dawley rats. Expression of c-Fos, a marker of neuronal activity, was assessed within the ACC using immunohistochemistry. Optogenetic inhibition of glutamatergic neurons of the ACC abolished F-CPA without affecting formalin-induced nociceptive behavior during conditioning. In male rats, optogenetic activation of ACC glutamatergic neurons decreased formalin-induced nociceptive behavior during conditioning without affecting F-CPA. Interestingly, the opposite effect was seen in females, where optogenetic activation of glutamatergic neurons of the ACC increased formalin-induced nociceptive behavior during conditioning. The abolition of F-CPA following optogenetic inhibition of glutamatergic neurons of the ACC was associated with a reduction in c-Fos immunoreactivity in the ACC in male rats, but not female rats. These results suggest that excitatory glutamatergic neurons of the ACC play differential and sex-dependent roles in the aversion learning and acute sensory components of pain.

Current perspectives on sex differences in tension-type headache

INTRODUCTION

Clinical and experimental evidence supports the presence of several gender differences in the pain experience.

AREAS COVERED

The current paper discusses biological, psychological, emotional, and social differences according to gender and their relevance to TTH. Gender differences have also been observed in men and women with tension-type headache and they should be considered by clinicians managing this condition. It appears that multimodal treatment approaches lead to better outcomes in people with tension-type headache; however, management of tension-type headache should consider these potential gender differences. Different studies have observed the presence of complex interactions between tension-type headache, emotional stress, sleep, and burden and that these interactions are different between men and women.

EXPERT OPINION

Based on current results, the authors hypothesize that treatment of men with tension-type headache should focus on the improvement of sleep quality and the level of depression whereas treatment of women with TTH should focus on nociceptive mechanisms and emotional/stressful factors. Future trials should investigate the proposed hypotheses.

Progesterone and Allopregnanolone Rapidly Attenuate Estrogen-Associated Mechanical Allodynia in Rats with Persistent Temporomandibular Joint Inflammation

Temporomandibular joint disorder (TMD) is associated with pain in the joint (temporomandibular joint, TMJ) and muscles involved in mastication. TMD pain dissipates following menopause but returns in some women undergoing estrogen replacement therapy. Progesterone has both anti-inflammatory and antinociceptive properties, while estrogen's effects on nociception are variable and highly dependent on both natural hormone fluctuations and estrogen dosage during pharmacological treatments, with high doses increasing pain. Allopregnanolone, a progesterone metabolite and positive allosteric modulator of the GABAA receptor, also has antinociceptive properties. While progesterone and allopregnanolone are antinociceptive, their effect on estrogen-exacerbated TMD pain has not been determined. We hypothesized that removing the source of endogenous ovarian hormones would reduce inflammatory allodynia in the TMJ of rats and both progesterone and allopregnanolone would attenuate the estrogen-provoked return of allodynia. Baseline mechanical sensitivity was measured in female Sprague-Dawley rats (150-175 g) using the von Frey filament method followed by a unilateral injection of complete Freund's adjuvant (CFA) into the TMJ. Mechanical allodynia was confirmed 24 h later; then rats were ovariectomized or received sham surgery. Two weeks later, allodynia was reassessed and rats received one of the following subcutaneous hormone treatments over 5 days: a daily pharmacological dose of estradiol benzoate (E2; 50 μg/kg), daily E2 and pharmacological to sub-physiological doses of progesterone (P4; 16 mg/kg, 16 μg/kg, or 16 ng/kg), E2 daily and interrupted P4 given every other day, daily P4, or daily vehicle control. A separate group of animals received allopregnanolone (0.16 mg/kg) instead of P4. Allodynia was reassessed 1 h following injections. Here, we report that CFA-evoked mechanical allodynia was attenuated following ovariectomy and daily high E2 treatment triggered the return of allodynia, which was rapidly attenuated when P4 was also administered either daily or every other day. Allopregnanolone treatment, whether daily or every other day, also attenuated estrogen-exacerbated allodynia within 1 h of treatment, but only on the first treatment day. These data indicate that when gonadal hormone levels have diminished, treatment with a lower dose of progesterone may be effective at rapidly reducing the estrogen-evoked recurrence of inflammatory mechanical allodynia in the TMJ.

Linking Pain Sensation to the Autonomic Nervous System: The Role of the Anterior Cingulate and Periaqueductal Gray Resting-State Networks

There are bi-directional interactions between the autonomic nervous system (ANS) and pain. This is likely underpinned by a substantial overlap between brain areas of the central autonomic network and areas involved in pain processing and modulation. To date, however, relatively little is known about the neuronal substrates of the ANS-pain association. Here, we acquired resting state fMRI scans in 21 healthy subjects at rest and during tonic noxious cold stimulation. As indicators of autonomic function, we examined how heart rate variability (HRV) frequency measures were influenced by tonic noxious stimulation and how these variables related to participants’ pain perception and to brain functional connectivity in regions known to play a role in both ANS regulation and pain perception, namely the right dorsal anterior cingulate cortex (dACC) and periaqueductal gray (PAG). Our findings support a role of the cardiac ANS in brain connectivity during pain, linking functional connections of the dACC and PAG with measurements of low frequency (LF)-HRV. In particular, we identified a three-way relationship between the ANS, cortical brain networks known to underpin pain processing, and participants’ subjectively reported pain experiences. LF-HRV both at rest and during pain correlated with functional connectivity between the seed regions and other cortical areas including the right dorsolateral prefrontal cortex (dlPFC), left anterior insula (AI), and the precuneus. Our findings link cardiovascular autonomic parameters to brain activity changes involved in the elaboration of nociceptive information, thus beginning to elucidate underlying brain mechanisms associated with the reciprocal relationship between autonomic and pain-related systems.

The effect of the menstrual cycle on running economy

BACKGROUND

The aim of this study was to examine the effect of the menstrual cycle on running economy (RE).

METHODS

Using a repeated-measures design, ten eumenorrheic, trained female runners (age: 32±6 yrs, V̇O2max: 59.7±4.7 mL·kg-1·min-1) completed four, weekly, identical sub-maximal and maximal incremental step tests on a treadmill to measure physiological responses across a full menstrual cycle. For phase comparison, the results from the trials that fell in the early follicular (low estrogen, low progesterone), late follicular (high estrogen, low progesterone) and mid-luteal (high estrogen, high progesterone) phases were used.

RESULTS

There was a significant effect of menstrual cycle phase on RE (P=0.001), with RE in the mid-luteal (ML) phase being worse than that of the early follicular (EF) (+2.33 mL·kg-1·min-1; P=0.026) and late follicular (LF) (+2.17 mL·kg-1·min-1; P=0.011) phases. The ML phase also resulted in elevated core temperature versus the EF (+0.51 ºC; P=0.001) and LF (+0.66 ºC; P=0.037) phases, and elevated minute ventilation versus the EF phase (+3.83 L·min-1; P=0.003). No significant effects of menstrual cycle phase were found on body mass, heart rate, ratings of perceived exertion, time-to-exhaustion, maximal oxygen consumption, or blood lactate concentration.

CONCLUSIONS

In the ML phase, which causes increased core temperature and minute ventilation, RE is impaired at exercise intensities that are applicable to training and performance. In physiologically stressful environments, this impairment in RE may have a significant impact on training and performance.

The Relationship Between Musculoskeletal Pain and Picky Eating: The Role of Negative Self-Labeling

Introduction

Picky eating appears to be associated with poor health outcomes and thus it might have a role in musculoskeletal pain in adults. However, this relationship has not been investigated yet. The aim of the present study was to determine whether the number of musculoskeletal pain regions was associated with picky eating, which was characterized by food intake balance of familiar products or self-identification.

Methods

A total of 4660 adult subjects were enrolled in this study. Picky eating was assessed in two ways; a countable score and self-identification of picky eating. For the countable score, the number of food items, which the subjects usually did not consume among a list of 11 familiar products was measured. Self-identification as a picky eater was defined through a single question. The presence of musculoskeletal pain; in the neck, low back, knee, back, or arm, within 2 months of the survey was also identified.

Results

Of all subjects, 2654 (56%) had musculoskeletal pain in at least one region. The prevalence of musculoskeletal pain in every region was seen as consistently higher in subjects who self-identified as picky eaters than those who were non-picky eaters. In multiple linear regression analysis, the number of pain regions was significantly associated with older age, females, self-identification as a picky eater, and low body weight, not but the countable score.

Conclusions

There may be an association between musculoskeletal pain and negative beliefs about one’s own eating behaviors.

Electronic supplementary material

The online version of this article (10.1007/s40122-019-0116-2) contains supplementary material, which is available to authorized users.

Ovarian Hormone-dependent and Spinal ERK Activation-regulated Nociceptive Hypersensitivity in Female Rats with Acid Injection-induced Chronic Widespread Muscle Pain

Symptoms of chronic widespread muscle pain (CWP) meet most of the diagnostic criteria for fibromyalgia syndrome, which is prevalent in females. We used an acid injection-induced muscle pain (AIMP) model to mimic CWP. After female rats received an ovariectomy (OVX), acid saline solution was injected into the left gastrocnemius muscle. Time courses of changes in pain behaviours and p-ERK in the spinal cord were compared between groups. Intrathecal injections of oestradiol (E2) to the OVX group before two acid injections and E2 or progesterone (P4) injections in male rats were compared to evaluate hormone effects. We found that repeated acid injections produced mechanical hypersensitivity and enhanced p-ERK expression in the spinal dorsal horn. OVX rats exhibited significantly less tactile allodynia than did the rats in the other groups. The ERK inhibitor U0126 alleviated mechanical allodynia with lower p-ERK expression in the sham females but did not affect the OVX rats. Intrathecal E2 reversed the attenuated mechanical hypersensitivity in the OVX group, and E2 or P4 induced transient hyperalgesia in male rats. Accordingly, our results suggested that ovarian hormones contribute to AIMP through a spinal p-ERK-mediated pathway. These findings may partially explain the higher prevalence of fibromyalgia in females than males.

Gender differences in temporomandibular disorders in adult populational studies: A systematic review and meta-analysis

The objective of this study was to systematically evaluate gender differences in the prevalence of TMD. A systematic review was performed in PubMed, EMBASE, Web of Science and LILACS in duplicate by two independent reviewers. The inclusion criteria were cross-sectional studies that reported the prevalence of TMD for men and women and that used the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) Axis I group diagnostic criteria:(group I = muscle disorders; group II = disc displacements; group III = arthralgias/arthritis/arthrosis).To be eligible for inclusion, studies must include adult individuals (>18 years) from a non-clinical population (ie without pre-diagnosis of TMD); in other words, from population-based studies. There were no restrictions on the year and language of publication. The quality of the articles was assessed by an adapted version of the Newcastle-Ottawa Scale(NOS), and the publication bias was assessed by a funnel plot graph. Data were quantitatively analysed by meta-analysis using odds ratio (OR) as the measure effect. The electronic search retrieved a total of 6104 articles, of which 112 articles were selected for full-text reading according to the eligibility criteria. By means of manual search, one study was retrieved. Five articles were selected for meta-analysis with a combined sample of 2518 subjects. Women had higher prevalence of TMD in all RDC/TMD diagnostic groups. The meta-analysis yielded the following results: (a) OR = 2.24 for global TMD (groups I, II and III combined), (b) OR = 2.09 for group I, (c) OR = 1.6 for group II and (d) OR = 2.08 for group III. The importance of gender in the development of TMD has been demonstrated, with a two times greater risk of women to develop it as compared to men.

Mouse MRI shows brain areas relatively larger in males emerge before those larger in females

Sex differences exist in behaviors, disease and neuropsychiatric disorders. Sexual dimorphisms however, have yet to be studied across the whole brain and across a comprehensive time course of postnatal development. Here, we use manganese-enhanced MRI (MEMRI) to longitudinally image male and female C57BL/6J mice across 9 time points, beginning at postnatal day 3. We recapitulate findings on canonically dimorphic areas, demonstrating MEMRI’s ability to study neuroanatomical sex differences. We discover, upon whole-brain volume correction, that neuroanatomical regions larger in males develop earlier than those larger in females. Groups of areas with shared sexually dimorphic developmental trajectories reflect behavioral and functional networks, and expression of genes involved with sex processes. Also, post-pubertal neuroanatomy is highly individualized, and individualization occurs earlier in males. Our results demonstrate the ability of MEMRI to reveal comprehensive developmental differences between male and female brains, which will improve our understanding of sex-specific predispositions to various neuropsychiatric disorders.

Sex differences occur in various aspects of neurodevelopment. Here the authors use manganese-enhanced MRI at nine different postnatal stages to detail the development of structural sex differences in the mouse brain.

Influence of Sexual Hormones on Neural Orofacial Perception

Objective

To investigate the trigeminal somatosensory (thermal, pain, tactile, vibratory, and electric), gustative (salty, bitter, sweet, sour), and olfactory thresholds in healthy women during the menstrual cycle and investigate any association with estradiol and progesterone levels in saliva.

Methods

We examined/tested 39 women between age 19 and 47 years and with regular menstrual cycles and no comorbidities. All women were informed about the purposes of the study, and only those who signed the informed consent were included. The tests were performed at three stages within the cycle: menstrual phase, follicular phase, and luteal phase. The procedure consisted of saliva collection at the beginning of each session to measure hormone levels, salivary flow, somatosensory evaluation with quantitative sensory testing applied to the right trigeminal maxillary branch and right forearm, gustative (sweet [glucose], salt [sodium chloride], sour [citric acid], and bitter [urea]) and olfactory (isopropanol at different concentrations) thresholds.

Results

During the menstrual cycle, thresholds for sweet, salty, sour, cold, vibration, and deep pain decreased, but warmth, electrical, and superficial pain thresholds increased. The bitter threshold was high, and the olfactory threshold was low in the follicular phase. Low estrogen levels were correlated to high deep pain thresholds in the forearm ( P  = 0.008) and face ( P  = 0.041), high tactile thresholds ( P  = 0.001), and high superficial pain ( P  = 0.006) thresholds in the face. High levels of progesterone were associated with a high deep pain threshold in the face and a high salty threshold ( P  < 0.001).

Conclusion

Estrogen and progesterone seem to be involved in sensory neuromodulation in women during the menstrual cycle.

Dental fear among transgender individuals - a cross-sectional survey

AIMS

The aims of this study were to: (1) evaluate the level of dental fear among transgender individuals and (2) investigate specific predictors of dental fear in individuals who identify as transgender.

METHOD AND RESULTS

An anonymous survey among transgender adults was conducted using both a web-based and paper survey. The survey included the Dental Fear Survey (DFS), history of hormonal interventions, perceived gender roles, and demographic information. The bivariate analyses did not show a significant difference in DFS between sex assigned at birth (p = 0.628) or among gender identities (p = 0.109). A regression model analysis for the level of DFS by using participants' demographic information as independent variables indicated the fear and experience of discrimination/maltreatment were significant predictors of dental fear; standardized beta coefficients (p-value) were 0.35 (p = 0.017) and 0.28 (p = 0.041), respectively.

CONCLUSION

The fear and experiences of discrimination/maltreatment were significantly positively associated with their level of dental fear.

Sex-based differences in brain alterations across chronic pain conditions

Common brain mechanisms are thought to play a significant role across a multitude of chronic pain syndromes. In addition, there is strong evidence for the existence of sex differences in the prevalence of chronic pain and in the neurobiology of pain. Thus, it is important to consider sex when developing general principals of pain neurobiology. The goal of the current Mini-Review is to evaluate what is known about sex-specific brain alterations across multiple chronic pain populations. A total of 15 sex difference and 143 single-sex articles were identified from among 412 chronic pain neuroimaging articles. Results from sex difference studies indicate more prominent primary sensorimotor structural and functional alterations in female chronic pain patients compared with male chronic pain patients: differences in the nature and degree of insula alterations, with greater insula reactivity in male patients; differences in the degree of anterior cingulate structural alterations; and differences in emotional-arousal reactivity. Qualitative comparisons of male-specific and female-specific studies appear to be consistent with the results from sex difference studies. Given these differences, mixed-sex studies of chronic pain risk creating biased data or missing important information and single-sex studies have limited generalizability. The advent of large-scale neuroimaging databases will likely aid in building a more comprehensive understanding of sex differences and commonalities in brain mechanisms underlying chronic pain. © 2016 Wiley Periodicals, Inc.

Calcitonin alleviates hyperalgesia in osteoporotic rats by modulating serotonin transporter activity

Calcitonin may relieve pain by modulating central serotonin activity. Calcitonin partly reversed the hypersensitivity to pain induced by ovariectomy. This suggests that the anti-nociceptive effects of calcitonin in the treatment of osteoporosis may be mediated by alterations in neural serotonin transporter (SERT) activity.

INTRODUCTION

This study used a rat model of osteoporosis to evaluate the role of the cerebral serotonin system in the anti-nociceptive effect of calcitonin, a drug used to treat post-menopausal osteoporosis.

METHODS

Osteoporosis was induced in rats by ovariectomy (OVX). Rats were then randomized to the following four groups: sham operation, OVX, OVX plus calcitonin, or OVX plus alendronate.

RESULTS

OVX led to alterations in bone micro-architecture; alendronate strongly reversed this effect, and calcitonin moderately reversed this effect. OVX increased hyperalgesia (determined as the time for hind paw withdrawal from a heat source); calcitonin reduced this effect, but alendronate had no effect. OVX increased the expression of c-Fos (a neuronal marker of pain) in the thalamus; calcitonin strongly reversed this effect, and alendronate moderately reversed this effect. OVX also reduced SERT but increased 5-HT1A receptor expression and activity; calcitonin aggravated this effect, but alendronate had no effect on recovery of SERT/5-HT1A activity and expression.

CONCLUSIONS

Our study of a rat model of osteoporosis suggests that OVX-induced enhancement of the serotonergic system may protect against hyperalgesia. However, the anti-nociceptive effects of calcitonin in osteoporosis may be mediated by decreased neural SERT activity and increased activation of 5-HT1 receptors in the thalamus.