Mechanisms of pain modulation by sex hormones in migraine

Gender aspects of CGRP in migraine

Background

Migraine is two to three times more prevalent in women than in men, but the mechanisms involved in this gender disparity are still poorly understood. In this respect, calcitonin gene-related peptide (CGRP) plays a key role in migraine pathophysiology and, more recently, the functional interactions between ovarian steroid hormones, CGRP and the trigeminovascular system have been recognized and studied in more detail.

Aims

To provide an overview of CGRP studies that have addressed gender differences utilizing animal and human migraine preclinical research models to highlight how the female trigeminovascular system responds differently in the presence of varying ovarian steroid hormones.

Conclusions

Gender differences are evident in migraine. Several studies indicate that fluctuations of ovarian steroid hormone (mainly estrogen) levels modulate CGRP in the trigeminovascular system during different reproductive milestones. Such interactions need to be considered when conducting future animal and human experiments, since these differences may contribute to the development of gender-specific therapies.

Temporomandibular Disorders and Headache

Temporomandibular disorders (TMD) and primary headaches can be perpetual and debilitating musculoskeletal and neurological disorders. The presence of both can affect up to one-sixth of the population at any one time. Initially, TMDs were thought to be predominantly musculoskeletal disorders, and migraine was thought to be solely a cerebrovascular disorder. The further understanding of their pathophysiology has helped to clarify their clinical presentation. This article focuses on the role of the trigeminal system in associating TMD and migraine. By discussing recent descriptions of prevalence, diagnosis, and treatment of headache and TMD, we will further elucidate this relationship.

Sex differences in the epidemiology, clinical features, and pathophysiology of migraine

Migraine is two to three times more prevalent in women than men, and women report a longer attack duration, increased risk of headache recurrence, greater disability, and a longer period of time required to recover. Conditions recognised to be comorbid with migraine include asthma, anxiety, depression, and other chronic pain conditions, and these comorbidities add to the amount of disability in both sexes. Migraine-specifically migraine with aura-has been identified as a risk factor for vascular disorders, particularly in women, but because of the scarcity of data, the comparative risk in men has yet to be established. There is evidence implicating the role of female sex hormones as a major factor in determining migraine risk and characteristics, which accounts for sex differences, but there is also evidence to support underlying genetic variance. Although migraine is often recognised in women, it is underdiagnosed in men, resulting in suboptimal management and less participation of men in clinical trials.

Signs and symptoms of temporomandibular disorders in women and men

INTRODUCTION

Women are more likely to present temporomandibular disorders (TMD); however, studies comparing genders in Brazilian samples are rare.

PURPOSE

To analyze the proportion of men and women, as well as the association between gender and age, problem duration, and TMD symptoms in patients admitted to an university clinic for treatment.

METHODS

Interview and assessment data of protocols from 1,000 patients diagnosed with TMD were collected and analyzed and then divided into two groups, male (n = 177) and female (n = 823). The exploratory analysis was based on contingency tables and χ2 test was carried out. Subsequently, the logistic regression model was used and the odds ratios (OR) concerning the evaluated comparisons were calculated.

RESULTS

Females were more prevalent in the sample, and mean ages and TMD duration were similar between the groups, with higher occurrence in young adults (19 to 40 years old). The OR values showed an association between the female gender and the signs/symptoms of pain in the temporomandibular joint, pain in the facial muscles, neck and shoulders, headache, fatigue in the muscles of mastication, otologic symptoms, and dysphonia. Women had two times higher chances of presenting these symptoms than men.

CONCLUSION

In the sample of Brazilian patients with TMD, the number of women who presented a higher prevalence of painful symptoms was greater, followed by otologic symptoms and complaints of dysphonia. The prevalence of joint noise was similar in both studied groups.

The influence of migraine and female hormones on capsaicin-induced dermal blood flow

Background Migraine is much more common in females than in males, and occurrence is associated with changes in female sex hormones. Calcitonin gene-related peptide (CGRP) plays a key role in migraine, and variations in female sex hormones may affect CGRP sensitivity and/or production. Objectives Investigate repeatability, gender differences, influence of the menstrual cycle and of migraine on CGRP-dependent changes in dermal blood flow (DBF). Methods CGRP-dependent increases in DBF were assessed using laser Doppler perfusion imaging after topical application of 300 or 1000 µg capsaicin on the forearm of healthy subjects and migraine patients. Results In healthy males, DBF response did not vary over time and was comparable with DBF in male migraineurs. In healthy females, capsaicin-induced DBF responses to both doses of capsaicin were higher during menstruation compared to the late-secretory phase (p < 0.05); this menstrual cycle dependence was absent in female migraine patients. Compared to healthy subjects, female migraineurs displayed a higher DBF response both during menstruation and during the late-secretory phase (p < 0.05). Conclusions An increased capsaicin-induced, CGRP-mediated DBF response was observed during menstruation in healthy women, but in female migraine patients this increased response was not affected by the menstrual cycle.

Support for the Microgenderome: Associations in a Human Clinical Population

The 'microgenderome' provides a paradigm shift that highlights the role of sex differences in the host-microbiota interaction relevant for autoimmune and neuro-immune conditions. Analysis of cross-sectional self-report and faecal microbial data from 274 patients with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) suggests that commensal gut microorganisms may play both protective and deleterious roles in symptom expression. Results revealed significant sex-specific interactions between Firmicutes (Clostridium, Streptococcus, Lactobacillus and Enterococcus) and ME/CFS symptoms (including neurological, immune and mood symptoms), regardless of compositional similarity in microbial levels across the sexes. Extending animal studies, we provide support for the microgenderome in a human clinical population. Applied and mechanistic research needs to consider sex-interactions when examining the composition and function of human microbiota.

17β-Estradiol Enhances ASIC Activity in Primary Sensory Neurons to Produce Sex Difference in Acidosis-Induced Nociception

Sex differences have been reported in a number of pain conditions. Women are more sensitive to most types of painful stimuli than men, and estrogen plays a key role in the sex differences in pain perception. However, it is unclear whether there is a sex difference in acidosis-evoked pain. We report here that both male and female rats exhibit nociceptive behaviors in response to acetic acid, with females being more sensitive than males. Local application of exogenous 17β-estradiol (E2) exacerbated acidosis-evoked nociceptive response in male rats. E2 and estrogen receptor (ER)-α agonist 1,3,5-Tris(4-hydroxyphenyl)-4-propyl-1H-pyrazole, but not ERβ agonist 2,3-bis(4-hydroxyphenyl)-propionitrile, replacement also reversed attenuation of the acetic acid-induced nociceptive response in ovariectomized females. Moreover, E2 can exert a rapid potentiating effect on the functional activity of acid-sensing ion channels (ASICs), which mediated the acidosis-induced events. E2 dose dependently increased the amplitude of ASIC currents with a 42.8 ± 1.6 nM of EC50. E2 shifted the concentration-response curve for proton upward with a 50.1% ± 6.2% increase of the maximal current response to proton. E2 potentiated ASIC currents via an ERα and ERK1/2 signaling pathway. E2 also altered acidosis-evoked membrane excitability of dorsal root ganglia neurons and caused a significant increase in the amplitude of the depolarization and the number of spikes induced by acidic stimuli. E2 potentiation of the functional activity of ASICs revealed a peripheral mechanism underlying this sex difference in acetic acid-induced nociception.

P2Y2 receptor antagonists as anti-allodynic agents in acute and sub-chronic trigeminal sensitization: role of satellite glial cells

Trigeminal (TG) pain often lacks a satisfactory pharmacological control. A better understanding of the molecular cross-talk between TG neurons and surrounding satellite glial cells (SGCs) could help identifying innovative targets for the development of more effective analgesics. We have previously demonstrated that neuronal pro-algogenic mediators upregulate G protein-coupled nucleotide P2Y receptors (P2YRs) expressed by TG SGCs in vitro. Here, we have identified the specific P2YR subtypes involved (i.e., the ADP-sensitive P2Y1 R and the UTP-responsive P2Y2 R subtypes), and demonstrated the contribution of neuron-derived prostaglandins to their upregulation. Next, we have translated these data to an in vivo model of TG pain (namely, rats injected with Complete Freund's adjuvant in the temporomandibular joint), by demonstrating activation of SGCs and upregulation of P2Y1 R and P2Y2 R in the ipsi-lateral TG. To unequivocally link P2YRs to the development of facial allodynia, we treated animals with various purinergic antagonists. The selective P2Y2 R antagonist AR-C118925 completely inhibited SGCs activation, exerted a potent anti-allodynic effect that lasted over time, and was still effective when administration was started 6-days post induction of allodynia, i.e. under subchronic pain conditions. Conversely, the selective P2Y1 R antagonist MRS2179 was completely ineffective. Moreover, similarly to the anti-inflammatory drug acetylsalicylic acid and the known anti-migraine agent sumatriptan, the P2X/P2Y nonselective antagonist PPADS was only partially effective, and completely lost its activity under sub-chronic conditions. Taken together, our results highlight glial P2Y2 Rs as potential "druggable" targets for the successful management of TG-related pain.

Influences of gender on postoperative morphine consumption

BACKGROUND

Gender related differences on morphine consumption during postoperative period following abdominal surgeries.

MATERIALS AND METHODS

Four hundred and fifty ASA I & II patients of either sex (male =231, female = 219), between the age group of 18-65 y undergoing elective intra abdominal surgeries under general anaesthesia were included for the study. Patients with preexisting pain either acute or chronic preoperatively were excluded from the study. Anaesthesia and analgesia protocol during surgery was standardized. Postoperatively, a loading dose was given to achieve the visual analogue scale (VAS) of ≤30 and subjects were connected to patient control analgesia (PCA) pump containing 0.4 mg/ml of morphine configured to deliver a bolus dose (1 mg) with a 5 min lock-out period. The total analgesic requirements along with VAS (visual analog scale) score were analysed between males and females in the first 24 h postoperatively. All demographic data and between group comparisons were analysed with student t-test. Within group comparisons were done by using one-way-ANOVA test and Tukey's Honestly significant Difference test.

RESULTS

During the first 24 h, males consumed significantly higher amount of morphine (34.35 ± 6.68 mg) when compared to females (26.78 ± 7.14 mg), p < 0.001.

CONCLUSION

We conclude that men require more morphine in the postoperative period than women.

Gender differences in neurologic emergencies part I: a consensus summary and research agenda on cerebrovascular disease

Cerebrovascular neurologic emergencies including ischemic and hemorrhagic stroke, subarachnoid hemorrhage (SAH), and migraine are leading causes of death and disability that are frequently diagnosed and treated in the emergency department (ED). Although sex and gender differences in neurologic emergencies are beginning to become clearer, there are many unanswered questions about how emergency physicians should incorporate sex and gender into their research initiatives, patient evaluations, and overall management plans for these conditions. After evaluating the existing gaps in the literature, a core group of ED researchers developed a draft of future research priorities. Participants in the 2014 Academic Emergency Medicine consensus conference neurologic emergencies working group then discussed and approved the recommended research agenda using a standardized nominal group technique. Recommendations for future research on the role of sex and gender in the diagnosis, treatment, and outcomes pertinent to ED providers are described for each of three diagnoses: stroke, SAH, and migraine. Recommended future research also includes investigation of the biologic and pathophysiologic differences between men and women with neurologic emergencies as they pertain to ED diagnoses and treatments.

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.

Sex and the migraine brain

The brain responds differently to environmental and internal signals that relate to the stage of development of neural systems. While genetic and epigenetic factors contribute to a premorbid state, hormonal fluctuations in women may alter the set point of migraine. The cyclic surges of gonadal hormones may directly alter neuronal, glial and astrocyte function throughout the brain. Estrogen is mainly excitatory and progesterone inhibitory on brain neuronal systems. These changes contribute to the allostatic load of the migraine condition that most notably starts at puberty in girls.

Sex hormones in the modulation of irritable bowel syndrome

Compelling evidence indicates sex and gender differences in epidemiology, symptomatology, pathophysiology, and treatment outcome in irritable bowel syndrome (IBS). Based on the female predominance as well as the correlation between IBS symptoms and hormonal status, several models have been proposed to examine the role of sex hormones in gastrointestinal (GI) function including differences in GI symptoms expression in distinct phases of the menstrual cycle, in pre- and post-menopausal women, during pregnancy, hormonal treatment or after oophorectomy. Sex hormones may influence peripheral and central regulatory mechanisms of the brain-gut axis involved in the pathophysiology of IBS contributing to the alterations in visceral sensitivity, motility, intestinal barrier function, and immune activation of intestinal mucosa. Sex differences in stress response of the hypothalamic-pituitary-adrenal axis and autonomic nervous system, neuroimmune interactions triggered by stress, as well as estrogen interactions with serotonin and corticotropin-releasing factor signaling systems are being increasingly recognized. A concept of “microgenderome” related to the potential role of sex hormone modulation of the gut microbiota is also emerging. Significant differences between IBS female and male patients regarding symptomatology and comorbidity with other chronic pain syndromes and psychiatric disorders, together with differences in efficacy of serotonergic medications in IBS patients confirm the necessity for more sex-tailored therapeutic approach in this disorder.

The impact of comorbid migraine on quality-of-life outcomes after endoscopic sinus surgery

OBJECTIVES/HYPOTHESIS

Chronic rhinosinusitis (CRS) and migraine are common entities with overlapping symptomatology, yet little research exists that investigates the intersection of the two. This study seeks to investigate whether patients with CRS-with and without a migraine history-experience comparable quality-of-life (QOL) improvement after endoscopic sinus surgery (ESS).

STUDY DESIGN

Retrospective analysis of a prospective cohort.

METHODS

An adult population (n = 229) with medically refractory CRS was prospectively evaluated following ESS using disease-specific QOL surveys: the Rhinosinusitis Disability Index (RSDI), the Chronic Sinusitis Survey (CSS), and the Sinonasal Outcome Test-22 (SNOT-22). History of comorbid migraine was identified (n = 46), and preoperative and postoperative QOL was compared to patients without migraine (n = 183).

RESULTS

Patients migraine and CRS were more likely to be female (P = 0.023); experience allergies (P = 0.024), fibromyalgia (P = 0.009), and depression (P = 0.010); and be less likely to have nasal polyposis (P = 0.003). Objective measures of disease (endoscopy and computed tomography scores) were significantly lower in patients with migraine (P = 0.027 and P = 0.002, respectively), yet these patients scored lower on baseline RSDI and SNOT-22 scores (P = 0.025 and P = 0.019, respectively). QOL in both patients with and without migraine improved significantly after ESS (P ≤ 0.003) and by comparable magnitudes (P ≥ 0.062).

CONCLUSION

Patients with comorbid migraine and CRS are more likely to have less severe evidence of disease and worse preoperative baseline QOL scores. This may imply that comorbid migraine disorder, in the setting of CRS, compels these patients to seek surgical management earlier in the disease process. Regardless, ESS provides comparable improvement for both patients with and without comorbid migraine.

Temporo-mandibular disorders are an important comorbidity of migraine and may be clinically difficult to distinguish them from tension-type headache

Clinical differentiation between the primary headaches and temporomandibular disorders (TMD) can be challenging. Objectives : To investigate the relationship between TMD and primary headaches by conducting face to face assessments in patients from an orofacial pain clinic and a headache tertiary center. Method : Sample consists of 289 individuals consecutively identified at a headache center and 78 individuals seen in an orofacial pain clinic because of symptoms suggestive of TMD. Results : Migraine was diagnosed in 79.8% of headache sufferers, in headache tertiary center, and 25.6% of those in orofacial pain clinic (p<0.001). Tension-type headache was present in 20.4% and 46.1%, while the TMD painful occurred in 48.1% and 70.5% respectively (p<0.001). Conclusion : TMD is an important comorbidity of migraine and difficult to distinguish clinically from tension-type headache, and this headache was more frequent in the dental center than at the medical center.

Exposure to bisphenol A exacerbates migraine-like behaviors in a multibehavior model of rat migraine

Migraine is a common and debilitating neurological disorder suffered worldwide. Women experience this condition 3 times more frequently than men, with estrogen strongly implicated to play a role. Bisphenol A (BPA), a highly prevalent xenoestrogen, is known to have estrogenic activity and may have an effect in migraine onset, intensity, and duration through estrogen receptor signaling. It was hypothesized that BPA exposure exacerbates migraine symptoms through estrogen signaling and downstream activation of nociception related pathways. Utilizing a multibehavior model of migraine in ovariectomized female rats, changes in locomotion, light and sound sensitivity, grooming, and acoustic startle were examined. Furthermore, changes in the expression of genes related to estrogen (ERα, GPR30), and nociception (extracellular signal regulated kinase, ERK, sodium gated channel, Nav1.8, and fatty acid amide hydrolase, FAAH) were studied following behavioral experiments. The following results were obtained: BPA treatment significantly exacerbated migraine-like behaviors in rats. Rats exposed to BPA demonstrated decreased locomotion, exacerbated light and sound aversion, altered grooming habits, and enhanced startle reflexes. Furthermore, BPA exposure increased mRNA expression of estrogen receptors, total ERK mRNA and ERK activation, as well as Nav1.8, and FAAH mRNA, indicative of altered estrogen signaling and altered nociception. These results show that BPA, an environmentally pervasive xenoestrogen, exacerbates migraine-like behavior in a rat model and alters expression of estrogen and nociception-related genes.

The prevalence and clinical characteristics of primary headache in irritable bowel syndrome: a subgroup of the functional somatic syndromes

CONTEXT

The irritable bowel syndrome and primary headache are two chronic diseases characterized by symptoms of recurring pain and affect approximately 10%-20% of the general population.

OBJECTIVES

To study the prevalence of primary headache in volunteers with irritable bowel syndrome in a Brazilian urban community.

METHODS

It was evaluated the prevalence of primary headache associated with irritable bowel syndrome in adult volunteers 330 no patients.The protocol included the Rome III criteria, international classification of Headaches, later divided into four groups: I- Irritable bowel syndrome (n = 52), II- Primary headache (n = 45), III-Irritable bowel syndrome (n = 26) and headache, and IV- Controls (207).

RESULTS

We not found significant difference in the average age of the four groups and the diagnosis of irritable bowel syndrome, primary headache and their association was more frequent in females. The frequent use of analgesics was greater in groups II and III.

CONCLUSION

Our results suggest that irritable bowel syndrome and primary headache are also common in third world countries. The frequency in use of analgesics in association between the two entities was relevant. The identification of irritable bowel syndrome patients with different clinical sub-types could improve the therapeutics options and the prevention strategies.

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.

Patients profiling for Botox® (onabotulinum toxin A) treatment for migraine: a look at white matter lesions in the MRI as a potential marker

Background

To evaluate if white matter lesions (WML) on MRI can be a potential marker for onabotulinum toxin A (Botox®) treatment success in migraine, given the limited response rate and high costs per treatment.

Methods

Retrospective data base and MRI analysis of 529 migraineurs who received Botox® between 2002 and 2009. Responders were defined as patients who underwent three or more treatments, whereas non-responders had only one or two treatments. MRIs were analysed on axial T2 and coronar FLAIR (fluid attenuated inversion recovery) sequences for the presence of WML. Statistical analysis was done with the Chi-Square-Test and the Mann–Whitney-U-Test.

Results

Of 529 Botox® treated migraineurs, 111 patients had a MRI. Of these 111 patients, 47 were responders, 64 non-responders to Botox®. Response rate to Botox® in migraineurs with WML was 55.3%, in migraineurs without WML 44.7%. In the investigated items “age”, “age at onset”, “gender”, “attack duration”, “frequency”, “aura”, “WML”, “size of WML”, we found no statistical significant difference between the two groups. 55% of the responders and 50% of the non-responders showed WML. All WML were located supratentorially, anteriorly, mostly of small size (3–5 mm).

Conclusion

WML on MRIs cannot serve as a marker to predict a positive response to Botox®.

Evidence from neuroimaging for the role of the menstrual cycle in the interplay of emotion and cognition

Women show increased predisposition for certain psychiatric disorders, such as depression, that are associated with disturbances in the integration of emotion and cognition. While this suggests that sex hormones need to be considered as modulating factors in the regulation of emotion, we still lack a sound understanding of how the menstrual cycle impacts emotional states and cognitive function. Though signals for the influence of the menstrual cycle on the integration of emotion and cognition have appeared as secondary findings in numerous behavioral and neuroimaging studies, this has only very rarely been the primary research goal. This review summarizes evidence: (1) that the menstrual cycle modulates the integration of emotional and cognitive processing on a behavioral level, and (2) that this change in behavior can be associated with functional, molecular and structural changes in the brain during a specific menstrual cycle phase. The growing evidence for menstrual cycle-specific differences suggests a modulating role for sex hormones on the neural networks supporting the integration of emotional and cognitive information. It will further be discussed what methodological aspects need to be considered to capture the role of the menstrual cycle in the emotion-cognition interplay more systematically.

Irritable bowel syndrome and migraine: bystanders or partners?

Irritable bowel syndrome (IBS) and migraine are distinct clinical disorders. Apart from the characteristics of chronic and recurrent pain in nature, these pain-related disorders apparently share many similarities. For example, IBS is female predominant with community prevalence about 5-10%, whereas that of migraine is 1-3% also showing female predominance. They are often associated with many somatic and psychiatric comorbidities in terms of fibromyaglia, chronic fatigue syndrome, interstitial cystitis, insomnia and depression etc., even the IBS subjects may have coexisted migraine with an estimated odds ratio of 2.66. They similarly reduce the quality of life of victims leading to the social, medical and economic burdens. Their pathogeneses have been somewhat addressed in relation to biopsychosocial dysfunction, heredity, genetic polymorphism, central/visceral hypersensitivity, somatic/cutaneous allodynia, neurolimbic pain network, gonadal hormones and abuses etc. Both disorders are diagnosed according to the symptomatically based criteria. Multidisciplinary managements such as receptor target new drugs, melantonin, antispasmodics, and psychological drugs and measures, complementary and alternatives etc. are recommended to treat them although the used agents may not be necessarily the same. Finally, the prognosis of IBS is pretty good, whereas that of migraine is less fair since suicide attempt and stroke are at risk. In conclusion, both distinct chronic pain disorders to share many similarities among various aspects probably suggest that they may locate within the same spectrum of a pain-centered disorder such as central sensitization syndromes. The true pathogenesis to involve these disorders remains to be clarified in the future.

Epigenetic mechanisms in migraine: a promising avenue?

Migraine is a disabling common brain disorder typically characterized by attacks of severe headache and associated with autonomic and neurological symptoms. Its etiology is far from resolved. This review will focus on evidence that epigenetic mechanisms play an important role in disease etiology. Epigenetics comprise both DNA methylation and post-translational modifications of the tails of histone proteins, affecting chromatin structure and gene expression. Besides playing a role in establishing cellular and developmental stage-specific regulation of gene expression, epigenetic processes are also important for programming lasting cellular responses to environmental signals. Epigenetic mechanisms may explain how non-genetic endogenous and exogenous factors such as female sex hormones, stress hormones and inflammation trigger may modulate attack frequency. Developing drugs that specifically target epigenetic mechanisms may open up exciting new avenues for the prophylactic treatment of migraine.

Prevalence of and influencing factors for chronic headaches among pregnant women

OBJECTIVE

To determine the prevalence of headaches and their influencing factors among pregnant women.

METHODS

A cross-sectional study was conducted from January 3 to April 29, 2005, with 1357 women receiving routine pregnancy check-ups at the obstetric clinics of the community health institutions of Kayseri, Turkey. A structured questionnaire and the Zung Depression Scale were used to collect data.

RESULTS

Overall, 24.6% (95% confidence interval, 22.3%-26.9%) of the participants had headaches before pregnancy, whereas only 17.9% (95% confidence interval, 15.9%-20.1%) had headaches during pregnancy. Although the headache prevalence was lower during than before pregnancy, it was high among the participants aged 35 years or older, those who received help in their housework, and those who were multiparous. Moreover, the Zung depression score was significantly high among those experiencing headaches.

CONCLUSION

The significant decrease in headache prevalence observed during pregnancy may be the result of a pregnancy-specific hormonal status. However, the most significant factors influencing the frequency of headaches in the participants were related to their socioeconomic status and the severity of depression.

Sex differences in the expression of serotonin-synthesizing enzymes in mouse trigeminal ganglia

Migraine headaches are more prevalent in women and often occur during the early phases of the menstrual cycle, implying a link between migraine and ovarian steroids. Serotonin (5-HT) and its receptors have been proposed to play a key role in the pathophysiology of migraine. The trigeminal ganglion (TG) has been proposed as a site for 5-HT synthesis based on the expression of the rate limiting enzyme in peripheral 5-HT synthesis, tryptophan hydroxylase 1 (TPH1), in female rodent trigeminal ganglia. Tryptophan hydroxylase levels vary over the estrus cycle, however, the expression and potential regulation of other enzymes involved in 5-HT synthesis has not been reported in this tissue. C57/BL6 mice of both sexes expressed TPH1 and aromatic amino acid decarboxylase (AADC), the key enzymes involved in 5-HT synthesis. Levels of both enzymes were significantly higher in juvenile males compared with females. In naturally cycling females TPH1 and AADC expression was highest during proestrus when compared with the other phases of the cycle, and this regulation was mirrored at the mRNA level. In situ hybridization experiments detected TPH1 and AADC mRNA in presumptive neurons in the trigeminal ganglion. Both key enzymes involved in the synthesis of 5-HT are expressed in mouse trigeminal ganglion and are localized to neurons. The levels of these enzymes are dependent on gender and estrus cycle stage, suggesting that ovarian steroids might play a role in the regulation of sensory neuron 5-HT synthesis.