The influence of gender and sex steroids on craniofacial nociception

SIRT1-regulated ROS generation activates NMDAR2B phosphorylation to promote central sensitization and allodynia in a male chronic migraine rat model

Background

Central sensitization is one of the pivotal pathological mechanisms in chronic migraine (CM). Silent information regulator 1 (SIRT1) was shown to be involved in CM, but its specific mechanism is unclear. Reactive oxygen species (ROS) are increasingly regarded as important signaling molecules in several models of pain. However, studies about the role of ROS in the central sensitization of CM model are rare. We thus explored the specific process of SIRT1 involvement in the central sensitization of CM, focusing on the ROS pathway.

Methods

Inflammatory soup was repeatedly administered to male Sprague-Dawley rats to establish a CM model. The SIRT1 expression level in trigeminal nucleus caudalis (TNC) tissues was assessed by qRT-PCR and Western blotting analysis. The levels of ROS were detected by a Tissue Reactive Oxygen Detection Kit, DHE staining, and the fluorescence signal intensity of 8-OHdG. A ROS scavenger (tempol), a SIRT1 activator (SRT1720), a SIRT1 inhibitor (EX527), and a mitochondrial fission inhibitor (Mdivi-1) were used to investigate the specific molecular mechanisms involved. NMDAR2B, CGRP, ERK, and mitochondrial fission-related protein were evaluated by Western blotting, and the CGRP level in frozen sections of the TNC was detected via immunofluorescence staining.

Results

After repeated inflammatory soup infusion and successful establishment of the CM rat model, SIRT1 expression was found to be significantly reduced, accompanied by elevated ROS levels. Treatment with Tempol, SRT1720, or Mdivi-1 alleviated allodynia and reduced the increase in NMDAR2B phosphorylation and CGRP and ERK phosphorylation in the CM rat. In contrast, EX527 had the opposite effect in CM rat. SRT1720 and EX527 decreased and increased ROS levels, respectively, in CM rats, and tempol reversed the aggravating effect of EX527 in CM rats. Furthermore, the regulatory effect of SIRT1 on ROS may include the involvement of the mitochondrial fission protein DRP1.

Conclusion

The results indicate the importance of SIRT1 in CM may be due to its role in regulating the production of ROS, which are involved in modulating central sensitization in CM. These findings could lead to new ideas for CM treatment with the use of SIRT1 agonists and antioxidants.

Predictors of Non-Rhinogenic Facial Pain or Pressure in Otolaryngology Clinic

OBJECTIVES

Identify demographic and clinical characteristics that may help differentiate non-rhinogenic facial pain or pressure (NRFP) from sinusitis.

STUDY DESIGN

Retrospective single-institution study.

SETTING

Tertiary Care Center Rhinology Clinic.

METHODS

All patients presenting with a complaint of facial pain or pressure over a 3-year period were included. Patients were categorized into either NRFP or sinusitis groups based on computed tomography imaging and nasal endoscopy. Data pertaining to demographics, history, and SNOT-22 questionnaire domains were compared via univariate analysis as well as logistic regression with backwards variable selection.

RESULTS

A total of 296 patients met inclusion criteria, of which 128 had NRFP and 168 had sinusitis. A significantly greater percentage of patients in the NRFP group were women of childbearing age (40.6% vs 28.0%, P = .02). Backwards variable selection resulted in a model with four variables predicting a diagnosis of NRFP-female sex (odds ratio [OR] = 2.998, P < .0001), no history of prior sinonasal surgery (OR = 0.340 for history vs no history, P < .01), low nasal domain score (OR = 0.551, P < .0001), and high ear/facial domain score (OR = 1.453, P < .01).

CONCLUSION

Accurately identifying patients with NRFP at initial presentation based on history would help direct patients to the appropriate care pathway and prevent ineffective treatments such as antibiotics and sinus procedures. Our findings suggest that the suspicion for NRFP should be higher in women of child-bearing age as well as patients with greater ear/facial symptoms or lesser nasal symptoms.

Gender Differences in Pain Threshold, Unpleasantness, and Descending Pain Modulatory Activation Across the Adult Life Span: A Cross Sectional Study

The neurobiological underpinnings of gender differences in pain perception, and how these differences may be modified by age, are incompletely understood, placing patients at risk of suboptimal pain management. Using functional magnetic resonance imaging, we examined brain responses in the descending pain modulatory system (DPMS, specifically, dorsolateral prefrontal cortex, anterior cingulate cortex, insula, hypothalamus, amygdala, and periaqueductal gray, during an evoked pain task. We investigated the interaction of age and gender in our sample of healthy adults (27 females, 32 males, 30-86 years) on DPMS response. In a perceptually matched thermal pain paradigm, we investigated pain unpleasantness and neural responses for 3 heat pain percepts: just noticeable pain, weak pain, and moderate pain (MP). Females reported just noticeable pain at a lower temperature, but reported less unpleasantness at weak pain and MP percepts, compared to males. There was a significant age-by-gender interaction during moderate pain in the right anterior cingulate cortex and bilateral insula, such that, males had a stronger positive relationship between DPMS response and age compared to females in these regions. Our results indicate that differences in DPMS responses may explain some gender differences in pain perception and that this effect may change across the adult lifespan. PERSPECTIVE: Gender differences in pain have been well-documented but the brain mechanisms for these differences are still unclear. This article describes potential differences in brain functioning during different levels of pain that could explain differences in pain responses between men and women across the adult lifespan.

Pain-sensorimotor interactions: New perspectives and a new model

How pain and sensorimotor behavior interact has been the subject of research and debate for many decades. This article reviews theories bearing on pain-sensorimotor interactions and considers their strengths and limitations in the light of findings from experimental and clinical studies of pain-sensorimotor interactions in the spinal and craniofacial sensorimotor systems. A strength of recent theories is that they have incorporated concepts and features missing from earlier theories to account for the role of the sensory-discriminative, motivational-affective, and cognitive-evaluative dimensions of pain in pain-sensorimotor interactions. Findings acquired since the formulation of these recent theories indicate that additional features need to be considered to provide a more comprehensive conceptualization of pain-sensorimotor interactions. These features include biopsychosocial influences that range from biological factors such as genetics and epigenetics to psychological factors and social factors encompassing environmental and cultural influences. Also needing consideration is a mechanistic framework that includes other biological factors reflecting nociceptive processes and glioplastic and neuroplastic changes in sensorimotor and related brain and spinal cord circuits in acute or chronic pain conditions. The literature reviewed and the limitations of previous theories bearing on pain-sensorimotor interactions have led us to provide new perspectives on these interactions, and this has prompted our development of a new concept, the Theory of Pain-Sensorimotor Interactions (TOPSMI) that we suggest gives a more comprehensive framework to consider the interactions and their complexity. This theory states that pain is associated with plastic changes in the central nervous system (CNS) that lead to an activation pattern of motor units that contributes to the individual's adaptive sensorimotor behavior. This activation pattern takes account of the biological, psychological, and social influences on the musculoskeletal tissues involved in sensorimotor behavior and on the plastic changes and the experience of pain in that individual. The pattern is normally optimized in terms of biomechanical advantage and metabolic cost related to the features of the individual's musculoskeletal tissues and aims to minimize pain and any associated sensorimotor changes, and thereby maintain homeostasis. However, adverse biopsychosocial factors and their interactions may result in plastic CNS changes leading to less optimal, even maladaptive, sensorimotor changes producing motor unit activation patterns associated with the development of further pain. This more comprehensive theory points towards customized treatment strategies, in line with the management approaches to pain proposed in the biopsychosocial model of pain.

Sex-dependent differences in the genomic profile of lingual sensory neurons in naïve and tongue-tumor bearing mice

Mechanisms of sex-dependent orofacial pain are widely understudied. A significant gap in knowledge exists about comprehensive regulation of tissue-specific trigeminal sensory neurons in diseased state of both sexes. Using RNA sequencing of FACS sorted retro-labeled sensory neurons innervating tongue tissue, we determined changes in transcriptomic profiles in males and female mice under naïve as well as tongue-tumor bearing conditions Our data revealed the following interesting findings: (1) FACS sorting obtained higher number of neurons from female trigeminal ganglia (TG) compared to males; (2) Naïve female neurons innervating the tongue expressed immune cell markers such as Csf1R, C1qa and others, that weren't expressed in males. This was validated by Immunohistochemistry. (3) Accordingly, immune cell markers such as Csf1 exclusively sensitized TRPV1 responses in female TG neurons. (4) Male neurons were more tightly regulated than female neurons upon tumor growth and very few differentially expressed genes (DEGs) overlapped between the sexes, (5) Male DEGs contained higher number of transcription factors whereas female DEGs contained higher number of enzymes, cytokines and chemokines. Collectively, this is the first study to characterize the effect of sex as well as of tongue-tumor on global gene expression, pathways and molecular function of tongue-innervating sensory neurons.

Sex-dependent Differences in the Genomic Profile of Lingual Sensory Neurons in Naïve and Tongue-Tumor Bearing Mice

Mechanisms of sex-dependent orofacial pain are widely understudied. A significant gap in knowledge exists about comprehensive regulation of tissue-specific trigeminal sensory neurons in diseased state of both sexes. Using RNA sequencing of FACS sorted retro-labeled sensory neurons innervating tongue tissue, we determined changes in transcriptomic profiles in males and female mice under naïve as well as tongue-tumor bearing conditions Our data revealed the following interesting findings: 1) Tongue tissue of female mice was innervated with higher number of trigeminal neurons compared to males; 2) Naïve female neurons innervating the tongue exclusively expressed immune cell markers such as Csf1R, C1qa and others, that weren't expressed in males. This was validated by Immunohistochemistry. 4) Accordingly, immune cell markers such as Csf1 exclusively sensitized TRPV1 responses in female TG neurons. 3) Male neurons were more tightly regulated than female neurons upon tumor growth and very few differentially expressed genes (DEGs) overlapped between the sexes, 5) Male DEGs contained higher number of transcription factors whereas female DEGs contained higher number of enzymes, cytokines and chemokines. Collectively, this is the first study to characterize the effect of sex as well as of tongue-tumor on global gene expression, pathways and molecular function of tongue-innervating sensory neurons.

Development, validation and psychometric evaluation of the Chinese version of the biopsychosocial impact scale in orofacial pain patients

Background

The objective of this study was to develop the Chinese version of the biopsychosocial impact scale (BPIm-S) to assess functional limitation and psychosocial distress in orofacial pain (OFP) patients in mainland China, and investigate the factor structure, reliability and validity, measurement invariance, as well as scores differences across genders, age and educational status among OFP patients.

Methods

The BPIm-S was developed and evaluated in four stages: (1) concept selection and item generation; (2) a pilot study assessing face and content validity; (3) the factors structure, reliability, convergent validity, and measurement invariance; and (4) concurrent validity and clinical responsiveness. Exploratory (EFA) and confirmatory factor analyses (CFA) were performed on data gathered from 406 OFP patients to assess construct validity. Composite Reliability (CR) and the Average Variance Extracted (AVE) were used to assess internal convergent validity. CR, internal consistency, and split-half reliability were also performed to determine the reliability. Multigroup CFA (MGCFA) was used to assess measurement invariance across genders, age and educational status. Mann-Whitney test compared scores across different genders, age and educational status. Participants completed the BPIm-S, visual analog scale (VAS), brief pain inventory facial (BPI-F), General Anxiety Disorder-7 (GAD-7) and Patient Health Questionnaire-9 (PHQ-9), and spearman's correlation coefficient was used to evaluate the concurrent validity and item-total correlations. A total of 12 patients with OFP completed the BPIm-S twice to test clinical responsiveness. To conduct the CFA and measurement invariance analysis, Mplus 8.4 was used. IBM SPSS Statistics 21 software and SPSSAU, a web-based data science algorithm platform tool, were used for all additional studies.

Results

For the preliminary version, 17 items were chosen. A total of four items were removed following the pilot research. The remaining 13 items of the BPIm-S comprised an overall summary scale. Excellent reliability (Item-to-total correlations ranged from 0.763 to 0.912) and strong internal consistency (Cronbach's α = 0.970, functional limitation, 0.962, and psychosocial distress, 0.977) were discovered. CFA also validated the structural validity of the 13-item scale. EFA was performed and a two-factor structure was investigated. In addition, MGCFA corroborated the measurement invariance of the BPIm-S across gender, age, and educational status. Patients over the age of 30, those with a medium level of education, and those with a low level of education showed substantially greater levels of functional limitation and psychological distress (Wilcoxon test, p < 0.001). Both concurrent validity and clinical responsiveness were assessed to be of good quality.

Conclusion

The BPIm-S demonstrated good psychometric qualities and is a reliable tool that can now be used by clinicians to evaluate functional limitation and psychosocial distress among OFP patient.

Dopamine receptor D2 regulates GLUA1-containing AMPA receptor trafficking and central sensitization through the PI3K signaling pathway in a male rat model of chronic migraine

Background

The pathogenesis of chronic migraine remains unresolved. Recent studies have affirmed the contribution of GLUA1-containing AMPA receptors to chronic migraine. The dopamine D2 receptor, a member of G protein-coupled receptor superfamily, has been proven to have an analgesic effect on pathological headaches. The present work investigated the exact role of the dopamine D2 receptor in chronic migraine and its effect on GLUA1-containing AMPA receptor trafficking.

Methods

A chronic migraine model was established by repeated inflammatory soup stimulation. Mechanical, periorbital, and thermal pain thresholds were assessed by the application of von Frey filaments and radiant heat. The mRNA and protein expression levels of the dopamine D2 receptor were analyzed by qRT‒PCR and western blotting. Colocalization of the dopamine D2 receptor and the GLUA1-containing AMPAR was observed by immunofluorescence. A dopamine D2 receptor agonist (quinpirole) and antagonist (sulpiride), a PI3K inhibitor (LY294002), a PI3K pathway agonist (740YP), and a GLUA1-containing AMPAR antagonist (NASPM) were administered to confirm the effects of the dopamine D2 receptor, the PI3K pathway and GULA1 on central sensitization and the GLUA1-containing AMPAR trafficking. Transmission electron microscopy and Golgi-Cox staining were applied to assess the impact of the dopamine D2 receptor and PI3K pathway on synaptic morphology. Fluo-4-AM was used to clarify the role of the dopamine D2 receptor and PI3K signaling on neuronal calcium influx. The Src family kinase (SFK) inhibitor PP2 was used to explore the effect of Src kinase on GLUA1-containing AMPAR trafficking and the PI3K signaling pathway.

Results

Inflammatory soup stimulation significantly reduced pain thresholds in rats, accompanied by an increase in PI3K-P110β subunit expression, loss of dopamine receptor D2 expression, and enhanced GLUA1-containing AMPA receptor trafficking in the trigeminal nucleus caudalis (TNC). The dopamine D2 receptor colocalized with the GLUA1-containing AMPA receptor in the TNC; quinpirole, LY294002, and NASPM alleviated pain hypersensitivity and reduced GLUA1-containing AMPA receptor trafficking in chronic migraine rats. Sulpiride aggravated pain hypersensitivity and enhanced GLUA1 trafficking in CM rats. Importantly, the anti-injury and central sensitization-mitigating effects of quinpirole were reversed by 740YP. Both quinpirole and LY294002 inhibited calcium influx to neurons and modulated the synaptic morphology in the TNC. Additional results suggested that DRD2 may regulate PI3K signaling through Src family kinases.

Conclusion

Modulation of GLUA1-containing AMPA receptor trafficking and central sensitization by the dopamine D2 receptor via the PI3K signaling pathway may contribute to the pathogenesis of chronic migraine in rats, and the dopamine D2 receptor could be a valuable candidate for chronic migraine treatment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s10194-022-01469-x.

[Hippocampus is involved in 17β-estradiol exacerbating experimental occlusal inter- ference-induced chronic masseter hyperalgesia in ovariectomized rats]

OBJECTIVE

To investigate the influence of chronic masseter hyperalgesia induced by 17β-estradiol (E2) and experimental occlusal interference (EOI) on underlying mechanism in hippocampus of ovariectomized (OVX) rats.

METHODS

In the study, 32 OVX rats were randomly divided into 4 groups (8 rats/group): The control group was OVX group, and 0 μg/d E2 (vehicle) injection was started 7 d after OVX without EOI; in the experimental group (1) OVX + E2 group, 80 μg/d E2 injection was started 7 d after OVX without EOI; in the experimental group (2) OVX + EOI group, vehicle injection was started 7 d after OVX and EOI was applied 17 d after OVX; in the experimental group (3) OVX + E2 + EOI group, 80 μg/d E2 injection was started 7 d after OVX and EOI was applied 17 d after OVX. Bilateral masseter muscle mechanical withdrawal thresholds were measured before OVX, 7 days after OVX (before E2 injection), 17 days after OVX (10 days after E2 injection and before EOI) and 24 days after OVX (7 days after EOI). Immunofluorescence staining was used to reveal phospho-extracellular signal regulated kinase 1/2 (p-ERK1/2)-positive neurons in CA3 of hippocampus. The protein expression of p-ERK1/2 in hippocampus was detected using Western Blot.

RESULTS

Compared with the control group [left side: (135.3±8.5) g, right side: (135.4±10.8) g], bilateral masseter muscle mechanical withdrawal thresholds of OVX+E2 group [left side: (113.3±5.6) g, right side: (112.5 ± 5.6) g] and OVX+EOI group [left side: (93.3±5.4) g, right side: 90.8±5.5) g] were decreased (P < 0.01). Bilateral masseter muscle mechanical withdrawal thresholds were significantly lower in OVX+E2+EOI group [left side: (81.2±6.2) g, right side: 79.8±7.7) g] than in the control, OVX+E2 and OVX+EOI groups (P < 0.05). The proportion of p-ERK1/2 positive neurons in the CA3 region of the hippocampus was increased in the control, OVX+E2, OVX+EOI and OVX+E2+EOI groups in turn, and the difference between the groups was statistically significant (P < 0.05). p-ERK1/2 protein expression was increased in the control, OVX+E2 and OVX+EOI groups in turn, but the difference was not statistically significant (P>0.05). p-ERK1/2 expression was significantly higher in OVX+E2+EOI group than in the other three groups (P < 0.05).

CONCLUSION

High concentration of E2 could exacerbated EOI-induced chronic masseter hyperalgesia in ovariectomized rats, and its central mechanism may be related to the upregulation of the phosphorylation of ERK1/2 in hippocampus.

Chronic Orofacial Pain: Models, Mechanisms, and Genetic and Related Environmental Influences

Chronic orofacial pain conditions can be particularly difficult to diagnose and treat because of their complexity and limited understanding of the mechanisms underlying their aetiology and pathogenesis. Furthermore, there is considerable variability between individuals in their susceptibility to risk factors predisposing them to the development and maintenance of chronic pain as well as in their expression of chronic pain features such as allodynia, hyperalgesia and extraterritorial sensory spread. The variability suggests that genetic as well as environmental factors may contribute to the development and maintenance of chronic orofacial pain. This article reviews these features of chronic orofacial pain, and outlines findings from studies in animal models of the behavioural characteristics and underlying mechanisms related to the development and maintenance of chronic orofacial pain and trigeminal neuropathic pain in particular. The review also considers the role of environmental and especially genetic factors in these models, focussing on findings of differences between animal strains in the features and underlying mechanisms of chronic pain. These findings are not only relevant to understanding underlying mechanisms and the variability between patients in the development, expression and maintenance of chronic orofacial pain, but also underscore the importance for considering the strain of the animal to model and explore chronic orofacial pain processes.

Sports-Related Craniofacial Injuries Among Pediatric and Adolescent Females: A National Electronic Injury Surveillance System Database Study

BACKGROUND

Number of female athletes continues to exponentially increase in all sports; however, available literature detailing craniofacial injuries remains scarce. Compared to male athletes, female athletes may experience different types of injuries. These may be related to sex differences such as craniofacial pain and dimensions. Thus, this study assesses the type of sport and craniofacial injuries that pediatric and adolescent female athletes sustain.

METHODS

National Electronic Injury Surveillance System was analyzed for all hospital admissions for young female athletes (5-24 years old) experiencing a sports-related craniofacial injury. These included contusions and abrasions, lacerations, fractures, and hematomas. Following sports were analyzed for craniofacial injury: basketball, golf, soccer, ice skating, swimming, softball, horseback riding, volleyball, field hockey, and football.

RESULTS

Most of the sports-related craniofacial injury occurred in female athletes who are between 10 and 19 years old. Across all age groups, softball (34.9%), basketball (28.1%), and soccer (15.6%) caused majority of the craniofacial injuries. The most common presenting craniofacial injury types were contusions and abrasions as well as lacerations.

CONCLUSIONS

There is a need for improved protective gear, such as face shields and low-impact balls, especially in softball and basketball. Physicians should consider the differences in female versus male and child versus adult injury pattern when treating female athletes in order to prevent long-term complications, such as scarring and depression. Overall, sports-related craniofacial injuries among female athletes need to be further examined as the epidemiology of their injuries and their health needs are unique.

Transient Receptor Potential (TRP) Ion Channels in Orofacial Pain

Orofacial pain, including temporomandibular joint disorders pain, trigeminal neuralgia, dental pain, and debilitating headaches, affects millions of Americans each year with significant population health impact. Despite the existence of a large body of information on the subject, the molecular underpinnings of orofacial pain remain elusive. Two decades of research has identified that transient receptor potential (TRP) ion channels play a crucial role in pathological pain. A number of TRP ion channels are clearly expressed in the trigeminal sensory system and have critical functions in the transduction and pathogenesis of orofacial pain. Although there are many similarities, the orofacial sensory system shows some distinct peripheral and central pain processing and different sensitivities from the spinal sensory system. Relative to the extensive review on TRPs in spinally-mediated pain, the summary of TRPs in trigeminally-mediated pain has not been well-documented. This review focuses on the current experimental evidence involving TRP ion channels, particularly TRPV1, TRPA1, TRPV4, and TRPM8 in orofacial pain, and discusses their possible cellular and molecular mechanisms.

Transcriptomic sex differences in sensory neuronal populations of mice

Many chronic pain conditions show sex differences in their epidemiology. This could be attributed to sex-dependent differential expression of genes (DEGs) involved in nociceptive pathways, including sensory neurons. This study aimed to identify sex-dependent DEGs in estrous female versus male sensory neurons, which were prepared by using different approaches and ganglion types. RNA-seq on non-purified sensory neuronal preparations, such as whole dorsal root ganglion (DRG) and hindpaw tissues, revealed only a few sex-dependent DEGs. Sensory neuron purification increased numbers of sex-dependent DEGs. These DEG sets were substantially influenced by preparation approaches and ganglion types [DRG vs trigeminal ganglia (TG)]. Percoll-gradient enriched DRG and TG neuronal fractions produced distinct sex-dependent DEG groups. We next isolated a subset of sensory neurons by sorting DRG neurons back-labeled from paw and thigh muscle. These neurons have a unique sex-dependent DEG set, yet there is similarity in biological processes linked to these different groups of sex-dependent DEGs. Female-predominant DEGs in sensory neurons relate to inflammatory, synaptic transmission and extracellular matrix reorganization processes that could exacerbate neuro-inflammation severity, especially in TG. Male-selective DEGs were linked to oxidative phosphorylation and protein/molecule metabolism and production. Our findings catalog preparation-dependent sex differences in neuronal gene expressions in sensory ganglia.

Is There Any MRI Pattern That Discriminates Female From Male Migraine Patients?

There has been accumulating evidence on sex disparity in incidence, prevalence, symptomology, and burden of migraine. Several neuroimaging studies on migraine patients attempted to unravel the mechanisms of the disease, yet very few of them examined the sex-related differences. Here, we will first discuss some of the reported neuroimaging patterns that discriminate females from males in migraine. We will then re-examine the salient neuroimaging findings in migraine and discuss them in relation to sex-related influences. Finally, we will discuss some of the intriguing recent data suggesting the presence of sex-specific traits in migraineurs. These findings may have potential implications for future neuroimaging studies to identify underlying correlating patterns in the brain to (1) explain the neural basis for higher prevalence of migraine in women, and (2) better understand migraine-specific changes during different stages of life in both men and women.

Cannabidiol, cannabinol and their combinations act as peripheral analgesics in a rat model of myofascial pain

OBJECTIVE

This study investigated whether local intramuscular injection of non-psychoactive cannabinoids, cannabidiol (CBD), cannabinol (CBN), cannabichromene (CBC) and their combinations can decrease nerve growth factor (NGF)-induced masticatory muscle sensitization in female rats.

DESIGN

In awake rats, changes in mechanical sensitivity induced by intramuscular injection of NGF and cannabinoids were measured by applying an electronic von Frey hair over the masseter muscle to measure the withdrawal response. The effect of CBD (5 mg/ml) and CBN (1 mg/ml) or their combinations CBD/CBN (1:1 mg/ml or 5:1 mg/ml) were assessed. To confirm a peripheral action, electrophysiological experiments were undertaken in anesthetized rats to examine whether intramuscular injections of CBD (5 mg/ml) and CBN (1 mg/ml) altered the mechanical threshold of masticatory muscle mechanoreceptors.

RESULTS

In behavioral experiments, CBD (5 mg/ml) or CBN (1 mg/ml) decreased NGF-induced mechanical sensitization. Combinations of CBD/CBN induced a longer-lasting reduction of mechanical sensitization than either compound alone. No significant change in mechanical withdrawal threshold was observed in the contralateral masseter muscles and no impairment of motor function was found with the inverted screen test after any of the treatments. Consistent with behavioral results, CBD (5 mg/ml), CBN (1 mg/ml) and the combination of CBD/CBN (1:1 mg/ml) increased the mechanical threshold of masseter muscle mechanoreceptors. However, combining CBD/CBN (5:1 mg/ml) at a higher ratio reduced the duration of this effect. This may indicate an inhibitory effect of higher concentrations of CBD on CBN.

CONCLUSIONS

These results suggest that peripheral application of these non-psychoactive cannabinoids may provide analgesic relief for chronic muscle pain disorders such as temporomandibular disorders and fibromyalgia without central side effects.

Prevalence of TMD and level of chronic pain in a group of Brazilian adolescents

AIMS

To determine the prevalence of temporomandibular disorders and associated factors in an adolescent sample from Recife, Brazil.

MATERIALS AND METHODS

A cross-sectional study was conducted with 1342 adolescents aged 10-17 years. The Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) was used by calibrated examiners to evaluate the presence and levels of chronic pain. To evaluate the socioeconomic conditions, the subjects answered the Brazilian Economic Classification Criteria (CCEB) questionnaire. Data were analyzed by means of binary logistic regression in SPSS.

RESULTS

The results showed that 33.2% of the subjects had TMD irrespective of age (p = 0.153) or economic class (p = 0.653). Statistically significant associations were found between TMD and female gender (p = 0.017), headache/migraine in the past six months (p<0.001), chronic pain (p<0.001) and chronic pain level (p<0.001). In the final model, logistic regression showed that the level of chronic pain and the headache/migraine in the past six months were related to the presence of TMD.

CONCLUSIONS

The prevalence of TMD was considered high (33.2%) and adolescents with chronic pain and headache in the past six months were more likely to have TMD.

CLINICAL RELEVANCE

The data contribute to the understanding of TMD among adolescents and to the development of preventive measures and polices to identify the dysfunction promptly.

Chronic 17β-estradiol pretreatment has pronociceptive effect on behavioral and morphological changes induced by orofacial formalin in ovariectomized rats

Background

The prevalence of craniofacial pain disorders show sexual dimorphism with generally more common appearance in women suggesting the influence of estradiol, but the exact cause remains unknown. The common point in the pathogenesis of these disorders is the activation of trigeminal system. One of the animal experimental models of trigeminal activation is the orofacial formalin test, in which we investigated the effect of chronic 17β-estradiol pretreatment on the trigeminal pain-related behavior and activation of trigeminal second-order neurons at the level of spinal trigeminal nucleus pars caudalis (TNC).

Methods

Female Sprague Dawley rats were ovariectomized and silicone capsules were implanted subcutaneously containing cholesterol in the OVX group and 17β-estradiol and cholesterol in 1:1 ratio in the OVX+E₂ group. We determined 17β-estradiol levels in serum after the implantation of capsules. Three weeks after operation, 50 µL of physiological saline or 1.5% of formalin solution was injected subcutaneously into the right whisker pad of rats. The time spent on rubbing directed to the injected area and c-Fos immunoreactivity in TNC was measured as the formalin-induced pain-related behavior, and as the marker of pain-related neuronal activation, respectively.

Results

The chronic 17β-estradiol pretreatment mimics the plasma levels of estrogen occurring in the proestrus phase and significantly increased the formalin-induced pain-related behavior and neuronal activation in TNC.

Conclusion

Our results demonstrate that the chronic 17β-estradiol treatment has strong pronociceptive effect on orofacial formalin-induced inflammatory pain suggesting modulatory action of estradiol on head pain through estrogen receptors, which are present in the trigeminal system.

Application of algometry in patients with cervical and lumbar radiculopathy

BACKGROUND

Algometry, as a highly sensitive method, provides an objective insight into the degree of pain, while the use of questionnaires can estimate the patient's psychological status in a simple way.

OBJECTIVE

This study was conducted in order to measure the pressure pain threshold in patients with cervical and lumbar radiculopathy and to find a possible association of pain with the anxiety and depression.

METHODS

The study examined 60 hospitalized patients with cervical radiculopathy and 60 patients with lumbar radiculopathy before starting and after finishing kinesitherapy. The research was conducted using the digital algometry device and Hospital Anxiety and Depression Scale.

RESULTS

There was no statistically significant difference in algometric values between the patients with cervical radiculopathy and the patients with lumbar radiculopathy. The program of rehabilitation did not lead to significant improvement in the level of pain. Females have a lower pressure pain threshold than males. Psychological factors greatly affect the pain.

CONCLUSIONS

The applied methods will provide the implementation of appropriate therapy and would achieve better verification of the results in a rehabilitation program. Radiculopathy in conservative therapy should be treated in cervical-thoracic and lumbar region together. Rehabilitation period for patients with radiculopathy have to be longer.

Pituitary Hormones and Orofacial Pain

Clinical and basic research on regulation of pituitary hormones, extra-pituitary release of these hormones, distribution of their receptors and cell signaling pathways recruited upon receptor binding suggests that pituitary hormones can regulate mechanisms of nociceptive transmission in multiple orofacial pain conditions. Moreover, many pituitary hormones either regulate glands that produce gonadal hormones (GnH) or are regulated by GnH. This implies that pituitary hormones may be involved in sex-dependent mechanisms of orofacial pain and could help explain why certain orofacial pain conditions are more prevalent in women than men. Overall, regulation of nociception by pituitary hormones is a relatively new and emerging area of pain research. The aims of this review article are to: (1) present an overview of clinical conditions leading to orofacial pain that are associated with alterations of serum pituitary hormone levels; (2) discuss proposed mechanisms of how pituitary hormones could regulate nociceptive transmission; and (3) outline how pituitary hormones could regulate nociception in a sex-specific fashion. Pituitary hormones are routinely used for hormonal replacement therapy, while both receptor antagonists and agonists are used to manage certain pathological conditions related to hormonal imbalance. Administration of these hormones may also have a place in the treatment of pain, including orofacial pain. Hence, understanding the involvement of pituitary hormones in orofacial pain, especially sex-dependent aspects of such pain, is essential to both optimize current therapies as well as provide novel and sex-specific pharmacology for a diversity of associated conditions.

Prevalence of TMJ Disorders among the Patients Attending the Dental Clinic of Ajman University of Science and Technology-Fujairah Campus, UAE

The objective of this study was to determine the prevalence of temporomandibular joint (TMJ) disorders (if any) among the patients attending the dental clinic (for routine dental treatment) of Ajman University of Science and Technology (AUST)-Fujairah campus, UAE, and its possible causes. A sample of 100 adult patients attending the dental clinic of AUST for different types of dental treatment were collected; the routine examination of the TMJ and possible disorders such as clicking, crepitation, limitation or deviation during mouth opening, or tenderness reveals that 41% of the sample experience varying degrees of disorders in the TMJ. Radiographs were taken if needed (panoramic radiograph). The information was collected and recorded for each patient through questionnaires.

Sex-related influences in migraine

Migraine is a common neurological disorder with significantly higher incidence and prevalence in women than men. The presentation of the disease in women is modulated by changes in sex hormones from adolescence to pregnancy and menopause. Yet, the effect of sex influences has often been neglected in both basic and clinical and in clinical management of the disease. In this review, evidence from epidemiological, clinical, animal, and neuroimaging studies on the significance of the sex-related influences in migraine is presented, and the unmet needs in each area are discussed. © 2016 Wiley Periodicals, Inc.

Parafunctional habits are associated cumulatively to painful temporomandibular disorders in adolescents

This cross-sectional study was designed to evaluate the effect of sleep bruxism, awake bruxism and parafunctional habits, both separately and cumulatively, on the likelihood of adolescents to present painful TMD. The study was conducted on a sample of 1,094 adolescents (aged 12-14). The presence of painful TMD was assessed using the Research Diagnostic Criteria for Temporomandibular Disorders, Axis I. Data on sleep bruxism, awake bruxism and parafunctional habits (nail/pen/pencil/lip/cheek biting, resting one's head on one's hand, and gum chewing) were researched by self-report. After adjusting for potential demographic confounders using logistic regression, each of the predictor variables (sleep bruxism, awake bruxism and parafunctional habits) was significantly associated with painful TMD. In addition, the odds for painful TMD were higher in the concomitant presence of two (OR=4.6, [95%CI=2.06, 10.37]) or three predictor (OR=13.7, [95%CI=5.72, 32.96]) variables. These findings indicate that the presence of concomitant muscle activities during sleep and awake bruxism and parafunctional habits increases the likelihood almost linearly of adolescents to present painful TMD.

Grading the intensity of nondental orofacial pain: identification of cutoff points for mild, moderate, and severe pain

Background

When assessing pain in clinical practice, clinicians often label pain as mild, moderate, and severe. However, these categories are not distinctly defined, and are often used arbitrarily. Instruments for pain assessment use more sophisticated scales, such as a 0–10 numerical rating scale, and apart from pain intensity assess pain-related interference and disability. The aim of the study was to identify cutoff points for mild, moderate, and severe nondental orofacial pain using a numerical rating scale, a pain-related interference scale, and a disability measurement.

Materials and methods

A total of 245 patients referred to the Facial Pain Unit in London were included in the study. Intensity and pain-related interference were assessed by the Brief Pain Inventory. Pain-related disability was assessed by the Chronic Graded Pain Scale. Average pain intensity (0–10) was classified into nine schemes with varying cutoff points of mild, moderate, and severe pain. The scheme with the most significant intergroup difference, expressed by multivariate analysis of variance, provided the cutoffs between mild, moderate, and severe pain.

Results

The combination that showed the greatest intergroup differences for all patients was scheme 47 (mild 1–4, moderate 5–7, severe 8–10). The same combination provided the greatest intergroup differences in subgroups of patients with temporomandibular disorder and chronic idiopathic facial pain, respectively. Among the trigeminal neuralgia patients alone, the combination with the highest intergroup differences was scheme 48 (mild 1–4, moderate 5–8, severe 9–10).

Conclusion

The cutoff points established in this study can discriminate in pain intensity categories reasonably well, and showed a significant difference in most of the outcome measures used.

The second to fourth digit ratio (2D:4D): a risk factor of migraine and tension-type headache

BACKGROUND

Migraine and Tension-type headache (TTH) are common and disabling primary headache disorders. They are more prevalent in females. The second to fourth digit ratio (2D:4D) is sexually dimorphic in humans and is considered to be a marker for the balance of prenatal testosterone and estrogen exposure. Therefore, we investigated the hypothesis that prenatal sex steroids constitute an independent risk factor for adult headaches later in life.

METHODS

A total of 891 individuals (303 males, 588 females) of 18-68 years in age (a mean of 37.0 ± 10.1 years), including 279 migraine, 300 TTH, and 312 healthy subjects were enrolled. The 2D:4D ratio was measured by a single investigator using a digital Vernier caliper.

RESULTS

The females in the migraine group had lower 2D:4D ratios than those in the control group (left hand: 0.947 ± 0.034 vs. 0.955 ± 0.038, p = 0.048; right hand: 0.952 ± 0.035 vs. 0.965 ± 0.037, p = 0.001). There was a similar relationship between the TTH group and the control group (left hand: 0.946 ± 0.034 vs. 0.955 ± 0.038, p = 0.034; right hand: 0.954 ± 0.035 vs. 0.965 ± 0.037, p = 0.005), although this was not observed in males. Males showed lower 2D:4D ratios than females for the right hand in the control group (0.954 ± 0.039 vs. 0.965 ± 0.037, p = 0.015). No significant difference was found in the left hand.

CONCLUSIONS

These results suggested that the 2D:4D ratio is a risk factor of migraine and TTH and that the balance of prenatal estrogen and testosterone in utero may impact adult primary headache disorders.

Effects of estrogen on the serotonergic system and calcitonin gene-related peptide in trigeminal ganglia of rats

BACKGROUND

The prevalence of migraine is 3-folds higher in females than in males, and it is intricately related to the levels of estrogen. Estrogen may regulate the expression of metabolic enzymes and receptors of serotonin and also calcitonin gene-related peptide (CGRP), which are implicated in migraine pathogenesis.

PURPOSE

To study the effects of estrogen on the components of serotonin system and CGRP in trigeminal ganglia of ovariectomized (OVX) rats.

METHODS

OVX rats were administered estrogen in silastic tubes and after 48 h, serum estrogen levels were determined. Trigeminal ganglia tissues were used for RT-PCRs of tryptophan hydroxylase (TPH), monoamine oxidase (MAO), serotonin receptors (5-HT1A, 5-HT1B, 5-HT2A), estrogen receptor (ER) and CGRP. Western blots of TPH and MAO were performed.

RESULTS

Estradiol administration to OVX rats increased TPH mRNA levels, while decreased MAO mRNA levels in trigeminal ganglia tissue. Western blot data correlate with the gene expression results. The decreased mRNA levels of serotonin receptors following ovariectomy were restored in estrogen-replenished rats. The induced gene expression of ER in OVX rats was restored following estrogen replenishment.

CONCLUSION

Estrogen levels affect the levels of serotonin metabolizing enzymes and its receptors besides CGRP levels. Since TPH and MAO levels regulate circulating and physiologically available serotonin content, the regulation of serotonin metabolizing enzymes suggest a plausible mechanism by which estrogen alleviates migraine in women.

Headache associated with temporomandibular disorders among young Brazilian adolescents

OBJECTIVE

To verify whether headaches (HAs) are associated with temporomandibular disorders (TMD) in young Brazilian adolescents.

METHODS

From a population sample, 3117 public school children (12 to 14 y) were randomly invited to participate in this study. TMD was assessed according to the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) Axis I, in addition to questions #3, #4, and #14 of Axis II history questionnaire. HAs were investigated with question #18 of RDC/TMD Axis II. Chronic TMD pain was considered as pain that has persisted for 6 months or more, as proposed by the International Association for the Study of Pain. The statistical analysis consisted of χ tests, odds ratio (OR), and logistic regression models, adopting a significance level of 5%.

RESULTS

The sample included 1307 individuals (a response rate of 41.93%), and 56.8% (n=742) were girls. Overall, 330 adolescents (25.2%) were diagnosed with painful TMD and 595 (45.5%) presented with HAs. Individuals presenting with HAs were more likely to present painful TMD (OR=4.94; 95% confidence interval [CI], 3.73-6.54, P<0.001), especially combined muscle and joint painful TMD (OR=7.58; 95% CI, 4.77-12.05, P<0.001). HAs also increased the risk to a higher magnitude for chronic TMD pain (OR=6.12; 95% CI, 4.27-8.78, P<0.0001). All estimated ORs remained essentially unchanged after adjusting for sex.

DISCUSSION

HAs were a potential risk factor for TMD in adolescents, and the risk was particularly higher for painful and chronic TMD. When HAs are present in young adolescents, a complete examination is strongly recommended with regard to the presence of painful TMD, and vice versa.

Behavioral effects and mechanisms of migraine pathogenesis following estradiol exposure in a multibehavioral model of migraine in rat

Migraine is one of the most common neurological disorders, leading to more than 1% of total disability reported and over 68 million visits to emergency rooms or physician's offices each year in the United States. Three times as many women as men have migraine, and while the mechanism behind this is not well understood, 17β-estradiol (estradiol) has been implicated to play a role. Studies have demonstrated that exposure to estrogen can lead to activation of inflammatory pathways, changes in sodium gated channel activity, as well as enhanced vasodilation and allodynia. Estradiol receptors are found in trigeminal nociceptors, which are involved in signaling during a migraine attack. The purpose of this study was to investigate the role of estradiol in migraine pathogenesis utilizing a multibehavioral model of migraine in rat. Animals were surgically implanted with a cannula system to induce migraine and behavior was assessed following exposure to a proestrus level of estradiol for total locomotor activity, light and noise sensitivity, evoked grooming patterns, and enhanced acoustic startle response. Results demonstrated decreased locomotor activity, increased light and noise sensitivity, altered facial grooming indicative of allodynia and enhanced acoustic startle. Further examination of tissue samples revealed increased expression of genes associated with inflammation and vasodilation. Overall, this study demonstrates exacerbation of migraine-like behaviors following exposure to estradiol and helps further explain the underlying mechanisms behind sex differences found in this common neurological disorder.

The neuroanatomy of sexual dimorphism in opioid analgesia

The influence of sex has been neglected in clinical studies on pain and analgesia, with the vast majority of research conducted exclusively in males. However, both preclinical and clinical studies indicate that males and females differ in both the anatomical and physiological composition of central nervous system circuits that are involved in pain processing and analgesia. These differences influence not only the response to noxious stimuli, but also the ability of pharmacological agents to modify this response. Morphine is the most widely prescribed opiate for the alleviation of persistent pain in the clinic; however, it is becoming increasingly clear that morphine is less potent in women compared to men. This review highlights recent research identifying neuroanatomical and physiological dimorphisms underlying sex differences in pain and opioid analgesia, focusing on the endogenous descending pain modulatory circuit.

Effects of gustatory nerve transection and/or ovariectomy on oral capsaicin avoidance in rats

The incidence of chronic oral pain such as burning mouth syndrome is greater in peri-menopausal females, and was postulated to be associated with gustatory nerve damage. We investigated whether bilateral transection of the chorda tympani, with or without accompanying ovariectomy, affected oral capsaicin avoidance in rats. Female rats had restricted access to 2 bottles, 1 bottle containing capsaicin (concentration range: 0.33-33 μM/L) and the other vehicle. Percent volume of capsaicin consumption and lick counts were measured. The concentration series was tested before and 0.5, 3, 6, 9, and 12 months after the following surgical procedures: (a) bilateral transection of the chorda tympani (CTx); (b) ovariectomy (OVx); (3) CTx plus OVx; or (4) sham CT surgery. Before surgery there was a concentration-dependent decrease in licks and volume of capsaicin consumed, with a threshold between 0.1 and 0.3 ppm. The majority of drink licks occurred during the first 9 minutes of access. Over the 12-month test period, the CTx group did not exhibit reduced capsaicin consumption, and consumed significantly more capsaicin at 6 and 9 months postsurgery. Rats in the OVx group consistently consumed significantly less capsaicin and exhibited significantly higher counts of capsaicin-evoked Fos-like immunoreactivity in the dorsomedial trigeminal subnucleus caudalis (Vc) compared to all other treatment groups. That CTx, with or without OVx, did not enhance capsaicin avoidance indicates that damage to the gustatory system does not disinhibit trigeminal nociceptive transmission.

Estrogenic influences in pain processing

Gonadal hormones not only play a pivotal role in reproductive behavior and sexual differentiation, they also contribute to thermoregulation, feeding, memory, neuronal survival, and the perception of somatosensory stimuli. Numerous studies on both animals and human subjects have also demonstrated the potential effects of gonadal hormones, such as estrogens, on pain transmission. These effects most likely involve multiple neuroanatomical circuits as well as diverse neurochemical systems and they therefore need to be evaluated specifically to determine the localization and intrinsic characteristics of the neurons engaged. The aim of this review is to summarize the morphological as well as biochemical evidence in support for gonadal hormone modulation of nociceptive processing, with particular focus on estrogens and spinal cord mechanisms.

Pain and temporomandibular disorders: a pharmaco-gender dilemma

Gender is the biggest risk factor in the development of temporomandibular disorders (TMD) and orofacial pain. Gender differences in pain thresholds, temporal summation, pain expectations, and somatic awareness exist in patients with chronic TMD or orofacial pain. There are gender differences in pharmacokenetics and pharmacodynamics of medications used to treat pain. A better understanding of the mechanisms that contribute to the increased incidence and persistence of chronic pain in females is needed. Future research will elucidate the sex effects on factors that protect against developing pain or prevent debilitating pain. Gender-based treatments for TMD and orofacial pain treatment will evolve from the translational research stimulated by this knowledge.

Temporomandibular disorders dysfunction in headache patients

OBJECTIVE

To identify the frequency of signs and symptoms of temporomandibular disorder (TMD) and its severity in individuals with headache.

STUDY DESIGN

60 adults divided into three groups of 20 individuals: chronic daily headache (CDH), episodic headache (EH) and a control group without headache (WH). Headache diagnosis was performed according to the criteria of International Headache Society and the signs and symptoms of TMD were achieved by using a clinical exam and an anamnestic questionnaire. The severity of TMD was defined by the temporomandibular index (TMI).

RESULTS

The TMD signs and symptoms were always more frequent in individuals with headache, especially report of pain in TMJ area (CDH, n=16; EH, n=12; WH, n=6), pain to palpation on masseter (CDH, n=19; EH, n=16; WH, n=11) which are significantly more frequent in episodic and chronic daily headache. The mean values of temporomandibular and articular index (CDH patients) and muscular index (CDH and EH patients) were statistically higher than in patients of the control group, notably the articular (CDH=0.38; EH=0.25;WH=0.19) and muscular (CDH=0.46; EH=0.51; WH=0.26) indices.

CONCLUSIONS

These findings allow us to speculate that masticatory and TMJ pain are more common in headache subjects. Besides, it seems that the TMD is more severe in headache patients.

Increased prevalence of geographic tongue in burning mouth complaints: a retrospective study

OBJECTIVES

The objective of this study was to assess the frequency of geographic tongue and fissured tongue (GFT) in patients with burning mouth syndrome (BMS). Our hypothesis was that benign soft tissue changes to the tongue, such as GFT, are associated with BMS.

STUDY DESIGN

Retrospective review of 161 patients with BMS and 87 TMJ dysfunction cases as control. Frequency of GFT and demographics for both groups was assessed.

RESULTS

In the BMS group, 26.7% of the subjects were diagnosed with GFT, whereas in the control group, 11.5% had GFT (P < .05). In the subgroup of BMS with GFT, the male-to-female ratio was approximately 1:2, whereas the male-to-female ratio of those with BMS and no GFT was approximately 1:5 (P < .05).

CONCLUSIONS

Our results demonstrate a higher than expected prevalence of GFT among patients with BMS compared with a control group of patients with TMJ. In males, GFT may be a significant predictor for BMS.

Correlation analysis of craniomandibular index and gothic arch tracing in patients with craniomandibular disorders

BACKGROUND/AIM

Complex etiology and symptomatology of craniomandibular dysfunction make the diagnosing and therapy of this disorder more difficult. The aim of this work was to assess the value of clinical and instrumental functional analyses in diagnosing of this type of disorders.

METHODS

In this study 200 subjects were examined, 15 with temporomandibular joint disorder. They were subjected to clinical functional analysis (Fricton-Shiffman) and instrumental functional analysis by using the method of gothic arch. The parameters of the gothic arch records were analyzed and subsequently compared among the subjects of the observed groups.

RESULTS

In the examined group of the population 7.5% of them were with craniomandibular dysfunction. The most frequent symptoms were sound in temporomandibular joint, painful sensitivity of the muscles on palpation and lateral turning of the lower jaw while opening the mouth. By analyzing the gothic arch records and comparing the obtained values between the observed groups it was assessed that: lateral and protrusion movements, lateral amplitude and the size of gothic arch were much bigger in the healthy subjects, and latero-lateral asymmetry was larger in the sick subjects. Latero-lateral dislocation of apex was recorded only in the sick subjects with average values of 0.22 +/- 0.130 mm. The correlation between the values of Fricton-Shiffman craniomandibular index and the parameters of the gothic arch records and latero-lateral amplitude and dislocation of apex records were established by correlative statistical analysis.

CONCLUSION

Functional analysis of orofacial system and instrumental analysis of lower jaw movements (gothic arch method) can be recommended as precise and simple methods in diagnosing craniomandibular dysfunctions.

Age-dependent intrathecal opioid escalation in chronic noncancer pain patients

BACKGROUND

Age and gender may exert important influences on opioid responsiveness and chronic pain. These effects have not been explored in the setting of chronic intrathecal (IT) opioid therapy. The objective of this study was to evaluate the effect of age and sex on IT opioid requirements during the first year after implantation of an intrathecal drug delivery system (IDDS) in chronic noncancer pain patients.

DESIGN

Retrospective study. METHODS AND PATIENT POPULATION: In this retrospective study, 135 chronic noncancer pain patients consecutively implanted with IDDSs for opioid therapy had their first year postimplant records examined.

RESULTS

Similar pain relief was achieved at 12 months after implant in both age groups. Relative to the dose at implant, younger patients had significantly higher rates of IT opioid dose escalation compared with older patients at 12 months (750 ± 450% in patients ≤50 years old vs 195 ± 120% in patients >50 years old, P < 0.001). Oral opioid consumption was significantly decreased at 12 months in the older patient population (140 ± 89 to 62 ± 35 mg/day at 12 months, P < 0.001, n = 85), while in the younger patient group, there was no change in oral opioid consumption (128 ± 81 mg/day to 105 ± 140 mg/day at 12 months, P = 0.65, n = 50). Gender-based analysis (55% males and 45% females) revealed similar reductions in pain scores during the first year postimplant. Oral opioid consumption was significantly higher in females (126 ± 138 mg) vs males (79 ± 89 mg) at 12 months postimplant; however, IT opioid dose escalation at 12 months postimplant was not statistically different between males and females.

CONCLUSION

IT opioid dose escalation occurs more steeply in the younger (under 50 years old) IDDS patient population without a concomitant significant decrease in oral consumption of opioids. Age-dependent changes may have important clinical implications on the effectiveness of IT opioid therapy in noncancer pain and its potential complications.

Estrogen receptors localization in the spinal trigeminal nucleus: an immunohistochemical study in humans

There is increasing evidence for estrogenic modulation of neurotransmission within the trigeminal pain pathway. It is also likely that the effects of estrogens may be influenced by the presence and localization of estrogen receptors (ERs) in a given brain area. To date, human data on the localization of ERs in the spinal trigeminal nucleus (STN), a key brain region in craniofacial nociception, are lacking. To ascertain whether ERs are expressed in the human STN, we performed immunohistochemical analysis on medulla oblongata samples taken from eight adult subjects (three men and five women; age range, 23-71 years) who had died from causes unrelated to neurologic or endocrine diseases. Paraffin-embedded sections at the level of the subnucleus caudalis and interpolaris were incubated with anti-estrogen receptor alpha (ERα) and anti-estrogen receptor beta (ERβ) antibodies. ERα immunoreactivity was detected in the nucleus and cytoplasm of neuronal and glial cells in the STN and in the nerve fibers within the spinal trigeminal tract in all eight subjects; ERβ immunoreactivity was observed in the cytoplasm of neuronal cells in five subjects. This study is the first to provide evidence in humans that ER immunoreactivity is detectable on neuronal and glial cells of the STN. The two ER subtypes exhibited different expression patterns, with higher expression levels of ERα than ERβ. The presence of ER-containing cells in the STN suggests that estrogens may directly affect trigeminal neuron excitability in humans.

Effect of estrogen therapy, soy isoflavones, and the combination therapy on the submandibular gland of ovariectomized rats

The objective of this study was to evaluate the effect of estrogen deficiency, estrogen therapy, and soy isoflavones on the salivary glands in female rats. Ninety-six animals were ovariectomized, and 24 were sham-operated. Among the ovariectomized rats, 24 received 17β-estradiol; 24 received isoflavone extract; 24 received a combination therapy of both; and 24 received water as placebo. The submandibular glands were histomorphometrically analyzed. As a result, the ANOVA test revealed that the hormonal deficiency affected the acini and the ducts of ovariectomized rats, reducing their percentage compared to the sham group. All treatments caused an increase in ducts and acini compared to the placebo group. It was concluded that the estrogen deficiency may be related to salivary gland function due to a reduction in the quantity of salivary acini and ducts secondary to ovariectomy. The estrogen therapy, soy isoflavone therapy, and the combination of both are effective in reducing the effects of ovariectomy on the salivary glands.

Hysterectomy and predictors for opioid prescription in a chronic pain clinic sample

OBJECTIVES

To describe the prevalence of hysterectomy for women aged 18-45 seeking treatment at a chronic pain clinic, to describe patient characteristics (pain intensity, age, smoking status, hormone replacement status, and psychosocial factors) based on opioid and hysterectomy status, and to determine whether hysterectomy status predicted receipt of opioid prescription.

DESIGN

Retrospective cross-sectional chart review.

PARTICIPANTS

Total 323 new female patients aged 18-45 who completed the Brief Pain Inventory-Short Form at initial evaluation at a chronic pain clinic during a 12-month period (July 2008-June 2009).

MEASURES

Data were collected from the Brief Pain Inventory and medical charts. Variables included opioid prescription, average pain intensity, pain type, age, hysterectomy status, smoking status, and pain-related dysfunction across domains measured by the Brief Pain Inventory. The association of opioid prescription with hysterectomy and other factors were determined by logistic regression.

RESULTS

Prevalence of hysterectomy was 28.8%. Average pain intensity was not associated with either hysterectomy or opioid prescription status. However, hysterectomy and high levels of pain-related dysfunction were significantly and independently associated with opioid prescription after adjusting for age and pain intensity. More than 85% of women with hysterectomy and high pain-related dysfunction had opioid prescription.

CONCLUSIONS

Hysterectomy may confer risk for pain-related dysfunction and opioid prescription in women 45 and younger. More research is needed to understand 1) how patient characteristics influence prescribing patterns and 2) the specific medical risks and consequences of chronic opioid therapy in this population.