Sex-Related Differences in Animal Models of Migraine Headache

Increasing adult neurogenesis protects mice from epilepsy

Neurogenesis occurs in the adult brain in the hippocampal dentate gyrus, an area that contains neurons which are vulnerable to insults and injury, such as severe seizures. Previous studies showed that increasing adult neurogenesis reduced neuronal damage after these seizures. Because the damage typically is followed by chronic life-long seizures (epilepsy), we asked if increasing adult neurogenesis would prevent epilepsy. Adult neurogenesis was selectively increased by deleting the pro-apoptotic gene Bax from Nestin-expressing progenitors. Tamoxifen was administered at 6 weeks of age to conditionally delete Bax in Nestin-CreERT2 Bax fl/fl mice. Six weeks after tamoxifen administration, severe seizures (status epilepticus; SE) were induced by injection of the convulsant pilocarpine. After mice developed epilepsy, seizure frequency was quantified for 3 weeks. Mice with increased adult neurogenesis exhibited fewer chronic seizures. Postictal depression was reduced also. These results were primarily in female mice, possibly because they were the more affected by Bax deletion than males, consistent with sex differences in Bax. The female mice with enhanced adult neurogenesis also showed less neuronal loss of hilar mossy cells and hilar somatostatin-expressing neurons than wild type females or males, which is notable because these two hilar cell types are implicated in epileptogenesis. The results suggest that selective Bax deletion to increase adult neurogenesis can reduce experimental epilepsy, and the effect shows a striking sex difference. The results are surprising in light of past studies showing that suppressing adult-born neurons can also reduce chronic seizures.

Female-selective mechanisms promoting migraine

Sexual dimorphism has been revealed for many neurological disorders including chronic pain. Prelicinal studies and post-mortem analyses from male and female human donors reveal sexual dimorphism of nociceptors at transcript, protein and functional levels suggesting different mechanisms that may promote pain in men and women. Migraine is a common female-prevalent neurological disorder that is characterized by painful and debilitating headache. Prolactin is a neurohormone that circulates at higher levels in females and that has been implicated clinically in migraine. Prolactin sensitizes sensory neurons from female mice, non-human primates and humans revealing a female-selective pain mechanism that is conserved evolutionarily and likely translationally relevant. Prolactin produces female-selective migraine-like pain behaviors in rodents and enhances the release of calcitonin gene-related peptide (CGRP), a neurotransmitter that is causal in promoting migraine in many patients. CGRP, like prolactin, produces female-selective migraine-like pain behaviors. Consistent with these observations, publicly available clinical data indicate that small molecule CGRP-receptor antagonists are preferentially effective in treatment of acute migraine therapy in women. Collectively, these observations support the conclusion of qualitative sex differences promoting migraine pain providing the opportunity to tailor therapies based on patient sex for improved outcomes. Additionally, patient sex should be considered in design of clinical trials for migraine as well as for pain and reassessment of past trials may be warranted.

Can upper cervical manual therapy affect the blink reflex in subjects with migraine and neck pain?

BACKGROUND

Neck pain is a common complaint among migraineurs possibly due to the anatomic connections between cervical and trigeminal afferents in the trigeminocervical complex (TCC). Manual therapy (MT) is used in the management of headache disorders, with demonstrable neurophysiological effects. The blink reflex (BR) is one method of analyzing neurophysiological effects in headache patients. The purpose of this study was to investigate the effect of upper cervical spine MT on BR in subjects with migraine and neck pain.

METHODS & MATERIALS

Twenty subjects were assigned to a medication plus MT (MedMT) group (n = 10) and medication plus sham MT (sham MT) group (n = 10). After random assignment, all patients underwent testing for the BR (R1, R2, R2c responses). Then, subjects in group MedMT and group sham MT received either 4 sessions of MT or sham MT to the upper cervical spine. After completion of the intervention, BR testing was repeated.

RESULTS

There were no significant differences in both side R1 latency between group MT and group sham MT (P > 0.050). For both sides, R2 latencies were significantly prolonged in MedMT group compared with sham MT group (P < 0.050). Subjects in MedMT group showed significant prolongation in right and left R2c latency compared with sham MT group (P < 0.050).

DISCUSSION

The present study demonstrated that upper cervical MT affected trigeminal nociceptive neurotransmission in subjects with migraine and neck pain as reflected by changes in the BR. The increase in BR late response latencies of BR indicates an inhibitory effect of upper cervical spine MT on the TCC in these subjects. Trial Registration: The trial design was registered at the Iranian Registry of Clinical Trials (IRCT ID: IRCT20160621028567N2, url: https://www.irct.ir/) before the first patient was enrolled.

The Anti-Calcitonin Gene-Related Peptide (Anti-CGRP) Antibody Fremanezumab Reduces Trigeminal Neurons Immunoreactive to CGRP and CGRP Receptor Components in Rats

Treatment with the anti-CGRP antibody fremanezumab is successful in the prevention of chronic and frequent episodic migraine. In preclinical rat experiments, fremanezumab has been shown to reduce calcitonin gene-related peptide (CGRP) release from trigeminal tissues and aversive behaviour to noxious facial stimuli, which are characteristic pathophysiological changes accompanying severe primary headaches. To further decipher the effects of fremanezumab that underlie these antinociceptive effects in rats, immunohistochemistry and ELISA techniques were used to analyse the content and concentration of CGRP in the trigeminal ganglion, as well as the ratio of trigeminal ganglion neurons which are immunoreactive to CGRP and CGRP receptor components, 1-10 days after subcutaneous injection of fremanezumab (30 mg/kg) compared to an isotype control antibody. After fremanezumab treatment, the fraction of trigeminal ganglion neurons which were immunoreactive to CGRP and the CGRP receptor components calcitonin receptor-like receptor (CLR) and receptor activity modifying protein 1 (RAMP1) was significantly lowered compared to the control. The content and concentration of CGRP in trigeminal ganglia were not significantly changed. A long-lasting reduction in CGRP receptors expressed in trigeminal afferents may contribute to the attenuation of CGRP signalling and antinociceptive effects of monoclonal anti-CGRP antibodies in rats.

Migraine and the Gender Divide

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

Headache prevalence in transgender and gender diverse youth: A single-center case-control study

OBJECTIVE

Assess the prevalence of headache in transgender and gender-diverse adolescents, comparing prevalence with and without exposure to gender-affirming hormone therapy.

BACKGROUND

Transgender and gender-diverse youth are an understudied group in whom we can study the effects of sex steroids on adolescents' development of headache. We hypothesized that transfeminine adolescents treated with estrogen would have higher odds of headache than those not treated, and that transmasculine adolescents treated with testosterone would have lower odds of headache than those not treated.

METHODS

This retrospective case-control study analyzed all patients seen at the Boston Children's Hospital Gender Multispecialty Service clinic from 2007 to 2017. Cases were defined as patients with headache, controls as those without headache, and exposure as treatment with gender-affirming hormone therapy (i.e., estrogen or testosterone). A computerized search identified cases that were then validated by chart review.

RESULTS

Fifty-two of the 763 transgender and gender-diverse patients seen were confirmed to have headache. Of 273 transfeminine patients 45% (123/273) received estrogen treatment. Transfeminine patients receiving estrogen were more likely to have headache than those not receiving estrogen (7% [9/123] vs. 1% [2/150]; odd ratio [OR] 5.84 (95% confidence interval [CI] 1.24-27.6), p = 0.026). Of 490 transmasculine patients, 46% (227/490) received testosterone. Transmasculine patients receiving testosterone were more likely to have headache than those not receiving testosterone (12% [28/227] vs. 5% (13/263); OR 2.71 (95% CI 1.37-5.4), p = 0.005).

CONCLUSION

Among transfeminine and transmasculine youth, those who received gender-affirming hormone therapy had higher odds of headache compared to those not taking gender-affirming hormone therapy. Further prospective studies to guide headache care of transgender and gender-diverse youth and adults are needed. Our results could be generalizable to other pediatric gender management clinics and may be worth discussing with patients considering treatment.

Sex and Gender Considerations in Episodic Migraine

Purpose of Review

We seek to update readers on recent advances in our understanding of sex and gender in episodic migraine with a two part series. In part 1, we examine migraine epidemiology in the context of sex and gender, differences in symptomatology, and the influence of sex hormones on migraine pathophysiology (including CGRP). In part 2, we focus on practical clinical considerations for sex and gender in episodic migraine by addressing menstrual migraine and the controversial topic of hormone-containing therapies. We make note of data applicable to gender minority populations, when available, and summarize knowledge on gender affirming hormone therapy and migraine management in transgender individuals. Finally, we briefly address health disparities, socioeconomic considerations, and research bias.

Recent Findings

Migraine is known to be more prevalent, frequent, and disabling in women. There are also differences in migraine co-morbidities and symptomatology. For instance, women are likely to experience more migraine associated symptoms such as nausea, photophobia, and phonophobia. Migraine pathophysiology is influenced by sex hormones, e.g., estrogen withdrawal as a known trigger for migraine. Other hormones such as progesterone and testosterone are less well studied. Relationships between CGRP (the target of new acute and preventive migraine treatments) and sex hormones have been established with both animal and human model studies. The natural course of migraine throughout the lifetime suggests a contribution from hormonal changes, from puberty to pregnancy to menopause/post-menopause. Treatment of menstrual migraine and the use of hormone-containing therapies remains controversial. Re-evaluation of the data reveals that stroke risk is an estrogen dose- and aura frequency-dependent phenomenon. There are limited data on episodic migraine in gender minorities. Gender affirming hormone therapy may be associated with a change in migraine and unique risks (including ischemic stroke with high dose estrogen).

Summary

There are key differences in migraine epidemiology and symptomatology, thought to be driven at least in part by sex hormones which influence migraine pathophysiology and the natural course of migraine throughout the lifetime. More effective and specific treatments for menstrual migraine are needed. A careful examination of the data on estrogen and stroke risk suggests a nuanced approach to the issue of estrogen-containing contraception and hormone replacement therapy is warranted. Our understanding of sex and gender is evolving, with limited but growing research on the relationship between gender affirming therapy and migraine, and treatment considerations for transgender people with migraine.

Dealing with Headache: Sex Differences in the Burden of Migraine- and Tension-Type Headache

OBJECTIVE

The aim of this study was to investigate sex differences in the burden of migraine and tension-type headache (TTH).

BACKGROUND

Migraine and TTH are more common in women than in men, with differences in comorbidities, treatment responses, disease-modifying factors, and ictal and interictal burden of disease. Information about sex-related influences on ictal and interictal burden is limited, and an increased understanding is mandatory to provide tailored individual treatment for female and male patients.

METHODS

Participants answered an online survey based on the EUROLIGHT questionnaire. Inclusion criteria were the consent to participate, complete responses to the diagnostic questions, and information about their sex. Sex differences were investigated using the Mann-Whitney U test or Chi-square test. For detecting factors that influence the burden of disease, we built binary regression models.

RESULTS

We included 472 (74.6% female) migraineurs and 161 (59.6% female) participants with TTH. Women with migraine reported significantly more problems in their love lives, more self-concealment, less feelings of being understood by family and friends, more interictal anxiety, a higher pain severity, and more depression and anxiety symptoms than men. For TTH, we did not find significant sex-related differences. A higher headache frequency was the factor that increased the burden of disease in female but not in male migraneurs.

CONCLUSION

The burden of disease was higher in women than men with migraine in many aspects, but not with TTH. Therefore, according to our results, there is a need for sex-specific precision medicine for migraine but not TTH. Controlling the headache frequency with a proper acute or prophylactic treatment and treating comorbid depression and anxiety symptoms is crucial to ease migraine's burden, especially in women.

Headache in transgender and gender-diverse patients: A narrative review

OBJECTIVE

To summarize the unique aspects of managing headache in gender minorities and current research in this area including the potential relationship between gender-affirming hormone therapy (GAHT) and headache.

BACKGROUND

The study of headache in gender minorities is intrinsically important. Gender minorities are medically underserved, and their medical care to date has been limited by socioeconomic disadvantages including stigma and an unsupportive clinical environment. Despite the rising population of transgender and gender-diverse adults and youth, headache research has also been limited. Knowledge of hormonal effects on headache in cisgender patients raises the question of possible effects of GAHT on transgender patients.

METHODS/RESULTS

The manuscript is a narrative review of current best practices in treating transgender patients, including the use of appropriate terminology and ways to create a supportive environment. It also contains current guidelines on GAHT and reviews drug-drug interactions and secondary headache related to hormone therapy. We also review transgender headache research and related research on hormonal effects on headache in cisgender individuals.

CONCLUSION

Creating a supportive environment for transgender and gender-diverse patients and being knowledgeable about GAHT are key to providing quality headache care. This review identifies further research needs for this population including the epidemiology of headache disorders in sexual minorities and the potential effects of GAHT on headache disorders in transgender patients.

Involvement of P2Y12 receptors in an NTG-induced model of migraine in male mice

BACKGROUND AND PURPOSE

P2Y₁₂ receptors (P2Y₁₂ Rs) are known to regulate different forms of pain and inflammation. In this study we investigated the participation of P2Y₁₂ Rs in an animal model of migraine.

EXPERIMENTAL APPROACH

We tested the effect of the centrally administered selective P2Y₁₂ R antagonist PSB-0739, and P2Y₁₂ R gene deficiency in acute nitroglycerin (NTG)-treated mice. Additionally, platelet depletion was used to investigate the role of platelet P2Y₁₂ Rs during migraine-like pain.

KEY RESULTS

NTG induced sensory hypersensitivity of C57BL/6 wild-type (P2ry12^+/+ ) mice, accompanied by an increase in c-fos and CGRP expression in the upper cervical spinal cord (C1-C2) and trigeminal nucleus caudalis (TNC). Similar changes were also observed in P2Y₁₂ R gene-deficient (P2ry12^-/- ) mice. Prophylactic intrathecal application of PSB-0739 reversed thermal hyperalgesia and head grooming time in wild-type mice but had no effect in P2ry12^-/- mice; furthermore, it was also effective when applied as a post-treatment. PSB-0739 administration suppressed the expression of c-fos in C1-C2 and TNC, and decrease C1-C2 levels of dopamine and serotonin in wild-type mice. NTG treatment itself did not change adenosine diphosphate (ADP)-induced platelet activation measured by CD62P upregulation in wild-type mice. Platelet depletion by anti-mouse CD41 antibody and clopidogrel attenuated NTG-induced thermal hypersensitivity and head grooming time in mice.

CONCLUSION AND IMPLICATIONS

Taken together, our findings show that acute inhibition of P2Y₁₂ Rs alleviates migraine-like pain in mice, by modulating the expression of c-fos, and platelet P2Y₁₂ Rs might contribute to this effect. Hence, it is suggested that the blockade of P2Y₁₂ Rs may have therapeutic potential against migraine.

An underrepresented majority: A systematic review utilizing allodynic criteria to examine the present scarcity of discrete animal models for episodic migraine

BACKGROUND

Despite increasing evidence differentiating episodic and chronic migraine, little work has determined how currently utilized animal models of migraine best represent each distinct disease state.

AIM

In this review, we seek to characterize accepted preclinical models of migraine-like headache by their ability to recapitulate the clinical allodynic features of either episodic or chronic migraine.

METHODS

From a search of the Pu bMed database for "animal models of migraine", "headache models" and "preclinical migraine", we identified approximately 80 recent (within the past 20 years) publications that utilized one of 10 different models for migraine research. Models reviewed fit into one of the following categories: Dural KCl application, direct electrical stimulation, nitroglycerin administration, inflammatory soup injection, CGRP injection, medication overuse, monogenic animals, post-traumatic headache, specific channel activation, and hormone manipulation. Recapitulation of clinical features including cephalic and extracephalic hypersensitivity were evaluated for each and compared.

DISCUSSION

Episodic migraineurs comprise over half of the migraine population, yet the vast majority of current animal models of migraine appear to best represent chronic migraine states. While some of these models can be modified to reflect episodic migraine, there remains a need for non-invasive, validated models of episodic migraine to enhance the clinical translation of migraine research.

Sex Differences in the Epilepsies and Associated Comorbidities: Implications for Use and Development of Pharmacotherapies

The epilepsies are common neurologic disorders characterized by spontaneous recurrent seizures. Boys, girls, men, and women of all ages are affected by epilepsy and, in many cases, by associated comorbidities as well. The primary courses of treatment are pharmacological, dietary, and/or surgical, depending on several factors, including the areas of the brain affected and the severity of the epilepsy. There is a growing appreciation that sex differences in underlying brain function and in the neurobiology of epilepsy are important factors that should be accounted for in the design and development of new therapies. In this review, we discuss the current knowledge on sex differences in epilepsy and associated comorbidities, with emphasis on those aspects most informative for the development of new pharmacotherapies. Particular focus is placed on sex differences in the prevalence and presentation of various focal and generalized epilepsies; psychiatric, cognitive, and physiologic comorbidities; catamenial epilepsy in women; sex differences in brain development; the neural actions of sex and stress hormones and their metabolites; and cellular mechanisms, including brain-derived neurotrophic factor signaling and neuronal-glial interactions. Further attention placed on potential sex differences in epilepsies, comorbidities, and drug effects will enhance therapeutic options and efficacy for all patients with epilepsy. SIGNIFICANCE STATEMENT: Epilepsy is a common neurological disorder that often presents together with various comorbidities. The features of epilepsy and seizure activity as well as comorbid afflictions can vary between men and women. In this review, we discuss sex differences in types of epilepsies, associated comorbidities, pathophysiological mechanisms, and antiepileptic drug efficacy in both clinical patient populations and preclinical animal models.

Are Migraine Patients at Increased Risk for Symptomatic Coronavirus Disease 2019 Due to Shared Comorbidities?

The coronavirus disease 2019 (COVID-19) pandemic has rapidly transformed the whole world and forced us to look through comorbid diseases and risk factors from a different perspective. COVID-19 shows some inherent risk factors like cardiovascular comorbidities independent from age, gender, and geographic location. One of the most peculiar features of the COVID-19 pandemic is that severe acute respiratory syndrome coronavirus 2 respiratory infections disproportionately impact patients with hypertension, diabetes, and other cardiovascular comorbidities rather than those with allergic respiratory diseases and immune-compromised conditions. Migraine is a complex neuro-vasculo-inflammatory disorder that is also packed frequently with certain medical conditions including vascular disorders, hypertension, allergic diseases such as asthma and systemic inflammatory disorders. Accordingly, 2 different questions arise during the pandemic: (1) Do share comorbidities of cardiovascular diseases and hypertension increase the risk of symptomatic COVID-19 for migraine patients? (2) Do comorbid allergic and atopic diseases, including asthma act as opposite influencers alongside with female gender? This paper focuses on the co-existence of comorbidities of COVID-19, in comparison with migraine, based on a wide clinical dataset and available reports. Discussed mechanisms include potential strategic roles of angiotensin-converting enzyme 2, angiotensin-II, and nucleotide oligomerization domain-like receptor family, pyrin domain containing 3 inflammasome, playing remarkable parts in the pathogenesis of COVID-19 and migraine. There are also some clues about the importance of endothelial and pericyte dysfunction and neuroinflammation in COVID-19 infection, related to complications and survival of the patients. The large epidemiological studies as well as basic research, focusing on migraine patients with COVID-19 will clarify these vital questions during the upcoming periods.

Giving Researchers a Headache - Sex and Gender Differences in Migraine

Migraine is a common neurovascular disorder affecting ~15% of the general population. Ranking second in the list of years lived with disability (YLD), people living with migraine are greatly impacted by this especially burdensome primary headache disorder. In ~30% of individuals with migraine, transient neurological symptoms occur (migraine aura) that further increase migraine burden. However, migraine burden is differential with respect to sex. Though one-year prevalences in childhood are similar, starting with puberty, migraine incidence increases at a much higher rate in females than males. Thus, migraine over the life course occurs in women three to four times more often than in men. Attacks are also more severe in women, leading to greater disability and a longer recovery period. The sex disparity in migraine is believed to be partly mediated through fluctuations in ovarian steroid hormones, especially estrogen and progesterone, although the exact mechanisms are not yet completely understood. The release of the neuropeptide calcitonin gene-related peptide (CGRP), followed by activation of the trigeminovascular system, is thought to play a key role in the migraine pathophysiology. Given the burden of migraine and its disproportionate distribution, the underlying cause(s) for the observed differences between sexes in the incidence, frequency, and intensity of migraine attacks must be better understood. Relevant biological as well as behavioral differences must be taken into account. To evaluate the scope of the existing knowledge on the issue of biological sex as well as gender differences in migraine, we conducted a systematized review of the currently available research. The review seeks to harmonize existing knowledge on the topic across the domains of biological/preclinical, clinical, and population-level research, which are traditionally synthesized and interpreted in isolation. Ultimately, we identify knowledge gaps and set priorities for further interdisciplinary and informed research on sex and gender differences as well as gender-specific therapies in migraine.

Effects of estrogen and progesterone on the neurogenic inflammatory neuropeptides: implications for gender differences in migraine

Neurogenic inflammation including calcitonin gene-related peptide (CGRP) and substance-P (SP) release plays a pivotal role in migraine pathogenesis. Prevalence of migraine is ~ 3 folds higher in women than in men, but its underlying mechanisms remained unclear. We investigated the effects of female sex hormones estrogen and progesterone on CGRP and SP in in-vivo and ex-vivo in rats of both sexes. For in-vivo experiments, male, female and ovariectomized rats were separated into four groups (n = 7) as control, estrogen, progesterone and estrogen + progesterone, respectively. Groups received daily intraperitoneal vehicle, 17β-estradiol, progesterone and 17β-estradiol + progesterone for 5 days, respectively. For ex-vivo experiments in both sexes, isolated trigeminal ganglia and hemiskull preparations were divided into four groups (n = 6 or 8), respectively, as in-vivo groups, and administered the same test substances. CGRP and SP contents in plasma and superfusates were determined using ELISA. In in-vivo experiments, 17β-estradiol decreased CGRP levels in males and SP levels in ovariectomized rats. Progesterone increased both CGRP and SP levels in females. Their combination decreased both CGRP and SP levels in males, and only SP levels in ovariectomized rats. In ex-vivo experiments, 17β-estradiol reduced CGRP release in males and SP release in females in trigeminal ganglia. While progesterone increased CGRP release in trigeminal ganglia, it reduced SP release from hemiskulls in both sexes. Their combination restored progesterone-mediated changes in neuropeptides releases in both trigeminal ganglia and hemiskulls in both sexes. Estrogen alleviates neurogenic inflammation through modulation of CGRP and SP release. Progesterone has dual effects on these neuropeptides in different sites associated with migraine pain.

Sex-Specific Pharmacotherapy for Migraine: A Narrative Review

Migraine is a common neurological disorder characterized by recurrent headache episodes that accompany sensory-motor disturbances, such as higher sensitivity to touch and light, extremity heaviness or weakness, and speech or language disabilities. Worldwide, migraine is one of the top 10 causes of disability and hence poses a huge economic burden to society. On average, migraine occurs in 12% of population but its occurrence is sexually dimorphic, as it is two to three times more prevalent in women than in men. This female to male ratio of migraine prevalence is age- and sex hormone-dependent. Advancements in understanding migraine pathogenesis have also revealed an association with both genetics and epigenetics. The severity of migraine, in terms of its attack duration, headache intensity, frequency, and occurrence of migraine-associated symptoms, has generally been reported to be greater in women. Sex differences in migraine disability and comorbidities, such as psychiatric disorders, have also been noted in some population-based studies. However, research on sex-related differences in response to migraine treatments is relatively scarce. Although a general observation is that women consume more medication than men for migraine treatment, strategies for the use of abortive and preventive medications for migraine are generally similar in both sexes. This narrative review summarizes available findings on sexually distinct responses to abortive and prophylactic pharmacotherapy of migraine. Basic experimental data and clinical findings will be presented, and potential mechanisms underlying sex-based responses will be discussed to highlight the importance and value of sex-based treatment in migraine research and practice.

Contribution of intraganglionic CGRP to migraine-like responses in male and female rats

Objective

To evaluate whether intraganglionic calcitonin gene-related peptide induced differential migraine-like responses in male and female rats.

Methods

Calcitonin gene-related peptide was injected in the trigeminal ganglion of male and female rats followed by assessment of periorbital mechanical allodynia with von Frey hairs. The influence of systemic treatment with sumatriptan or intraganglionic treatment with minocycline and propentofylline was determined on the calcitonin gene-related peptide-induced mechanical allodynia in male and female rats. One additional group was exposed to an aversive light 24 h after calcitonin gene-related peptide priming, followed by evaluation of periorbital mechanical threshold, and another group was tested in the elevated-plus maze.

Results

Intraganglionar calcitonin gene-related peptide-induced periorbital mechanical allodynia in female (0.5 to 6 h) and male rats (0.5 to 4 h). Systemic sumatriptan briefly attenuated the mechanical allodynia, but intraganglionar minocycline or propentofylline injection was effective only in male rats. Calcitonin gene-related peptide induced photic sensitivity in female and male rats (lasting 4 h and 1 h, respectively), as well as anxiety-like behavior.

Conclusions

Intraganglionar calcitonin gene-related peptide may play a major role in migraine-like responses, including periorbital mechanical allodynia, light sensitivity and anxiety like-behavior. Female rats are likely to be more susceptible to calcitonin gene-related peptide effects and a better understanding of the sexual dimorphism in calcitonin gene-related peptide signaling may help to improve migraine therapy.

Sex differences in the expression of calcitonin gene-related peptide receptor components in the spinal trigeminal nucleus

BACKGROUND AND PURPOSE

Calcitonin gene-related peptide (CGRP) plays an important role in migraine pathophysiology. CGRP acts primarily by activating a receptor composed of 3 proteins: calcitonin receptor-like receptor (CLR), receptor activity-modifying protein 1 (RAMP1), and receptor component protein (RCP). We tested the hypothesis that sex differences exist in protein levels of two key components of this CGRP receptor: CLR and RCP.

METHODS

We used specific antibodies to assess baseline protein levels of CLR and RCP in the spinal trigeminal nucleus caudalis (SpVc) and upper cervical spinal cord of both male and female rats. We also tested if manipulations that knock-down the expression of RCP in SpVc, using locally-mediated gene transfer of short hairpin RNA (shRNA), ameliorate pain in an animal model of intracranial migraine-like pain induced by chemical noxious stimulation of the meninges. To assess pain, we used tests of ongoing pain (rat face grimace test and freezing behavior) and tests of facial mechanical hypersensitivity and allodynia.

RESULTS

There was no difference in CLR levels between male and female animals (p > 0.11) in SpVc and the upper cervical cord. However, female animals exhibited greater baseline levels of RCP (up to 3-fold higher) compared to males (p < 0.002). The knock-down of RCP expression in SpVc attenuated mechanical facial allodynia induced by chemical noxious stimulation of the meninges, but had little effect on ongoing pain behaviors in female and male animals.

CONCLUSIONS

RCP is an integral component of the CGRP receptor and may play a key role in mediating CGRP induced central sensitization after noxious stimulation of the meninges. RCP expression in the SpVc and upper cervical cord is sexually dimorphic, with higher levels of expression in females. This dimorphism may be related to the increased incidence of migraines in females-a hypothesis that should be tested in the future.

Amplification of glyceryl trinitrate-induced headache features by noxious craniofacial stimuli in pain-free healthy humans

AIM

Glyceryl trinitrate (GTN) provokes an immediate migraine-like headache, followed by a delayed migraine attack in migraineurs. In healthy volunteers, only an immediate, less severe and shorter headache occurs. The presence of an already sensitized nervous system in migraineurs may underlie the more intense and prolonged GTN-evoked headaches. We tested if in healthy humans, application of noxious cutaneous and/or mechanical stimulation within craniofacial region would enhance or prolong GTN-evoked headache.

MATERIALS & METHODS

Noxious stimuli with a capsaicin patch on forehead, a mechanical headband, or both were applied prior to sublingual GTN (0.5 mg) in 20 healthy volunteers. GTN-induced headache characteristics and sensory responsiveness were recorded.

RESULTS

A more intense GTN-evoked headache was produced following application of headband.

CONCLUSION

Noxious mechanical stimulation prior to GTN resulted in a more intense GTN-evoked headache.

Male and female sex hormones in primary headaches

BACKGROUND

The three primary headaches, tension-type headache, migraine and cluster headache, occur in both genders, but all seem to have a sex-specific prevalence. These gender differences suggest that both male and female sex hormones could have an influence on the course of primary headaches. This review aims to summarise the most relevant and recent literature on this topic.

METHODS

Two independent reviewers searched PUBMED in a systematic manner. Search strings were composed using the terms LH, FSH, progesteron*, estrogen*, DHEA*, prolactin, testosterone, androgen*, headach*, migrain*, "tension type" or cluster. A timeframe was set limiting the search to articles published in the last 20 years, after January 1st 1997.

RESULTS

Migraine tends to follow a classic temporal pattern throughout a woman's life corresponding to the fluctuation of estrogen in the different reproductive stages. The estrogen withdrawal hypothesis forms the basis for most of the assumptions made on this behalf. The role of other hormones as well as the importance of sex hormones in other primary headaches is far less studied.

CONCLUSION

The available literature mainly covers the role of sex hormones in migraine in women. Detailed studies especially in the elderly of both sexes and in cluster headache and tension-type headache are warranted to fully elucidate the role of these hormones in all primary headaches.

Loss of Blood-Brain Barrier Integrity in a KCl-Induced Model of Episodic Headache Enhances CNS Drug Delivery

Cortical spreading depression (CSD) in the CNS is suggested as a common mechanism contributing to headache. Despite strong evidence for CNS involvement in headache disorders, drug development for headache disorders remains focused on peripheral targets. Difficulty in delivering drugs across the blood-brain barrier (BBB) may partially account for this disparity. It is known, however, that BBB permeability is increased during several CNS pathologies. In this study, we investigated BBB changes in response to KCl-induced CSD events and subsequent allodynia in rats. Cortical KCl injection in awake, freely moving rats produced facial allodynia with peak intensity between 1.5 and 3 h and CSD induction within 0.5-2 h postinjection. Brain perfusion of 14C-sucrose as a marker of BBB paracellular permeability revealed increased leak in the cortex, but not brainstem, beginning 0.5 h post-KCl injection and resolving within 6 h; no changes in tight junction (TJ) proteins occludin or claudin-5 expression were observed. Acute pretreatment with topiramate to inhibit CSD did not prevent the increased BBB paracellular permeability. CNS delivery of the abortive anti-migraine agent sumatriptan was increased in the cortex 1.5 h post-KCl injection. Surprisingly, sumatriptan uptake was also increased in the brainstem following CSD induction, suggesting regulation of active transport mechanisms at the BBB. Together, these results demonstrate the ability of CSD events to produce transient, time-dependent changes in BBB permeability when allodynia is present and to mediate access of clinically relevant therapeutics (i.e., sumatriptan) to the CNS.

Co-occurrence of migraine and atopy in children and adolescents: myth or a casual relationship?

PURPOSE OF REVIEW

To clarify the causal relationship between migraine and atopic disorders in children and adolescents.

RECENT FINDINGS

Migraine headache and atopic disorders including asthma are both common functional syndromes of childhood in which nature of the relationship is still debated. Attacks may induce in both disorders upon exposure to potential triggers in genetically susceptible individuals. Clinical phenotype manifests by temporary dysfunction of target tissue mediated by inflammation triggered by specific agents. Clinical features also change after puberty because of the partial effect of female sex hormones on the process. Appropriate definition of the syndrome and differentiating from other disorders are necessary not only for correct diagnosis, but also for planning of management strategies in children. Allergic rhinosinusitis needs to be differentiated from migraine even in experienced clinics. Questioning the presence of cranial autonomic symptoms is important clue in the differential diagnosis. Atopic disorder screening is particularly required in the diagnosis of migraine in childhood and adolescents. The link between both disorders of childhood seems to be far from a coincidence and some common inflammatory mechanisms are shared.

SUMMARY

On the basis of clinical features, laboratory findings and some practical clues in children, accurate diagnosis of migraine and atopic disorders are very critical for physicians, pediatricians and algologists.

17-β-Estradiol induces spreading depression and pain behavior in alert female rats

AIMS

Test the putative contribution of 17-β-estradiol in the development of spreading depression (SD) events and head pain in awake, non-restrained rats.

MAIN METHODS

Female, Sprague-Dawley rats were intact or underwent ovariectomy followed one week later by surgery to place electrodes onto the dura to detect epidural electroencephalographic activity (dEEG). dEEG activity was recorded two days later for 12 hours after systemic administration of 17-β-estradiol (180 μg/kg, i.p.). A separate set of rats were observed for changes in exploratory, ambulatory, fine, and rearing behaviors; periorbital allodynia was also assessed.

KEY FINDINGS

A bolus of 17-β-estradiol significantly elevated serum estrogen levels, increased SD episodes over a 12-hour recording period and decreased rearing behaviors in ovariectomized rats. Pre-administration of ICI 182,780, an estrogen receptor antagonist, blocked 17-β-estradiol-evoked SD events and pain behaviors; similar results were observed when the antimigraine therapeutic sumatriptan was used.

SIGNIFICANCE

These data indicate that an estrogen receptor-mediated mechanism contributes to SD events in ovariectomized rats and pain behaviors in both ovariectomized -and intact- rats. This suggests that estrogen plays a different role in each phenomenon of migraine where intense fluctuations in concentration may influence SD susceptibility. This is the first study to relate estrogen peaks to SD development and pain behaviors in awake, freely moving female rats, establishing a framework for future preclinical migraine studies.

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.

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.

Sex differences in vascular physiology and pathophysiology: estrogen and androgen signaling in health and disease

Sex differences between women and men are often overlooked and underappreciated when studying the cardiovascular system. It has been long assumed that men and women are physiologically similar, and this notion has resulted in women being clinically evaluated and treated for cardiovascular pathophysiological complications as men. Currently, there is increased recognition of fundamental sex differences in cardiovascular function, anatomy, cell signaling, and pathophysiology. The National Institutes of Health have enacted guidelines expressly to gain knowledge about ways the sexes differ in both normal function and diseases at the various research levels (molecular, cellular, tissue, and organ system). Greater understanding of these sex differences will be used to steer future directions in the biomedical sciences and translational and clinical research. This review describes sex-based differences in the physiology and pathophysiology of the vasculature, with a special emphasis on sex steroid receptor (estrogen and androgen receptor) signaling and their potential impact on vascular function in health and diseases (e.g., atherosclerosis, hypertension, peripheral artery disease, abdominal aortic aneurysms, cerebral aneurysms, and stroke).

Effectiveness of the progestin-only pill for migraine treatment in women: A systematic review and meta-analysis

Background Migraine is highly prevalent in women (18%). Peak morbidity affects their most productive years, coinciding with peak fertility. Hormonal contraception is often tailored for migraine prevention. Estrogen-containing contraceptives may be contraindicated in women experiencing migraine with aura due to the risk of vascular events. While improvements in migraine with a progestin-only pill (POP), which inhibits ovulation are documented, the strength and quality of evidence has not been formally evaluated. Objectives To determine the effectiveness of progestin-only contraceptives for migraine treatment by systematic review and meta-analysis. Data sources and selection MEDLINE, EMBASE and Cochrane Libraries were searched (1980 to September 2016) for studies on progestin-only treatments for migraine. Studies in English on >4 non-menopausal women aged 18-50 with migraine diagnosed by formal criteria were included. Data extraction and analysis Data were quality-assessed using the GRADE system. A random effects model was used for pooled analyses. Results Pooled analyses of four studies demonstrated that desogestrel 75 mcg/day, POP significantly but modestly reduced the number of migraine attacks and migraine days. Reduced intensity and duration, reduced analgesic and triptan use were observed, along with improved headache-related quality of life. GRADE analysis indicated evidence was low to very low for each outcome measure. Adverse effects resulted in treatment cessation for <10% of participants. Two studies compared desogestrel POP to a combined oral contraceptive, demonstrating similar migraine outcomes for both treatments. Conclusions The desogestrel POP shows promise in improving migraine in women. Current evidence is observational and based on small samples of women using only one oral progestin-only formulation. Further randomized trials on additional progestin-only contraceptives are required to confirm their role in migraine management.

Improvement of migraine with change from combined hormonal contraceptives to progestin-only contraception with desogestrel: How strong is the effect of taking women off combined contraceptives?

Migraine is a disabling headache disorder, which affects up to 17% of the female population. Oestrogen withdrawal during the menstrual cycle or the hormone-free interval in users of combined hormonal contraceptives (CHC) plays a pivotal role. Two diary-based studies demonstrated a positive impact of the progestin-only pill (POP) desogestrel 75 μg on the frequency of the migraine attacks and pain intensity. In both studies, CHC users as well as nonusers were included, which makes it difficult to distinguish between the effect of taking women off the CHC and the benefit of the POP itself. With the present study, we compared the therapeutic effect of the POP desogestrel 75 μg on migraine in current CHC users and nonusers. We found a positive influence of desogestrel on migraine not only in women who switched from CHCs to desogestrel, but also in those who had not used hormones over 6 months before starting it. Our findings need to be confirmed in prospectively conducted studies with larger sample size.

Diagnosing migraine

Migraine is a common headache disorder, particularly in women. It usually starts during the teens and twenties, a time when many women are seeking contraception advice. Migraine without aura is the most prevalent type of migraine, affecting up to 70% of people with migraine, while the remainder experience attacks with and/or without aura. Aura is a phase of focal neurological symptoms, typically visual. An increasing body of evidence identifies aura as a marker of increased risk of ischaemic stroke and its presence is a contraindication to the use of combined hormonal contraception (CHC). However, aura is often confused with more generalised premonitory visual symptoms of migraine that may precede attacks of migraine with and without aura, which are not associated with stroke risk. Diagnostic confidence is needed so that CHC is not withheld unnecessarily.

Positive effects of the progestin desogestrel 75 μg on migraine frequency and use of acute medication are sustained over a treatment period of 180 days

Background

Premenopausal migraines frequently are associated with fluctuations of estrogen levels. Both, migraine and combined hormonal contraceptives (CHC) increase the risk of vascular events. Therefore progestagen-only contraceptives (POC) are a safer alternative. A previous short-term study demonstrated a positive impact of the oral POC desogestrel on migraine frequency. To study the effect of the POC desogestrel 75 μg on migraine frequency, intensity, use of acute medication and quality of life in a clinical setting over the period of 180 days.

Methods

Patients’ charts were screened for women with migraine, who had decided to use desogestrel for contraception. Charts were included, if routinely conducted headache diaries were complete for 90 days before treatment (baseline) and over a treatment period of 180 days. We also report about starters who stopped treatment early, because of adverse events. Baseline data (day 1–90 before treatment) were compared with first and second treatment period (treatment days 1–90 and days 91–180). Quality of life was evaluated using MIDAS questionnaires.

Results

Days with migraine (5.8 vs 3.6), with any kind of headache (9.4 vs 6.6), headache intensity (15.7 vs 10.7), days with severe headache (5.4 vs 2.4) and use of triptans (12.3 vs7.8) were significantly reduced after 180 days. MIDAS score and grade improved significantly.

Conclusion

Contraception with desogestrel 75 μg resulted in a significantly improved quality of life and a reduction of migraine days over the observation period of 180 days. A clinically meaningful 30% reduction in pain was observed in 25/42 (60%) participants. For counselling reasons it is of importance, that the major reduction in migraine frequency occured during the initial 90 days, however further improvement occurs with longer duration of use. Prospective studies are needed to confirm these results.

Sex-related differences in migraine

This paper reviews sex-related differences in migraine epidemiology, symptoms, natural history and co-morbid disorders. Migraine is more than twice as common in females as in males, and women experience more frequent, longer lasting and more painful attacks, have more disability and a risk of transition from episodic to chronic migraine greater than men, but the mechanisms behind these differences are still poorly understood. The role of sex hormones, genes, and the differences in brain function and structure are discussed. Finally, we evaluate the many gender-related questions about treatment of migraine in women. In future research data should be analyzed separately for men and women to ensure that differences between the sexes could be identified.

Functional and sensory evaluation of patients with idiopathic trigeminal neuralgia: comparison with controls

BACKGROUND

Idiopathic trigeminal neuralgia (ITN) can be associated with orofacial and sensory comorbidities.

OBJECTIVE

To evaluate the masticatory functional and sensory characteristics of patients with ITN compared with controls.

METHODS

We enrolled 119 patients and 30 healthy controls. They were evaluated with a systematic protocol: clinical orofacial evaluation questionnaire; a systematic approach of the mandibular function and the investigation of musculoskeletal comorbidities by the research diagnostic criteria for temporomandibular disorders (RDC/TMD) and the Helkimo indexes; and quantitative sensory testing (corneal reflex and gustative, olfactory, thermal, mechanical and pain thresholds).

RESULTS

The study group had more loss of vertical dimension than the controls (p=0.011) and restriction of the maximum mouth opening (p=0.024); they had more pain on mandibular movements (p=0.001), limitation of mandibular function (p<0.001), masticatory discomfort (p<0.001) and myofascial pain (p=0.001). Occlusion Helkimo index was lower in controls than patients. The study group had high tactile (p=0.025), warm (p=0.020) and cold (p=0.003) thresholds.

CONCLUSION

ITN may cause severe mandibular limitations that can be associated with the pain episodes and with sensory abnormalities. These findings indicate the affection of small and large nerve fibers and support the neuropathic nature of ITN. Sensory alterations can be part of the natural history of ITN and can be associated with the previous treatments including medication. They cause a high impact in quality of life.

Migraine and estrogen

PURPOSE OF REVIEW

The aim is to systematically and critically review the relationship between migraine and estrogen, the predominant female sex hormone, with a focus on studies published in the last 18 months.

RECENT FINDINGS

Recent functional MRI (fMRI) studies of the brain support the existence of anatomical and functional differences between men and women, as well as between participants with migraine and healthy controls. In addition to the naturally occurring changes in endogenous sex hormones over the lifespan (e.g. puberty and menopause), exogenous sex hormones (e.g. hormonal contraception or hormone therapy) also may modulate migraine. Recent data support the historical view of an elevated risk of migraine with significant drops in estrogen levels. In addition, several lines of research support that reducing the magnitude of decline in estrogen concentrations prevents menstrually related migraine (MRM) and migraine aura frequency.

SUMMARY

Current literature has consistently demonstrated that headache, in particular migraine, is more prevalent in women as compared with men, specifically during reproductive years. Recent studies have found differences in headache characteristics, central nervous system anatomy, as well as functional activation by fMRI between the sexes in migraine patients. Although the cause underlying these differences is likely multifactorial, considerable evidence supports an important role for sex hormones. Recent studies continue to support that MRM is precipitated by drops in estrogen concentrations, and minimizing this decline may prevent these headaches. Limited data also suggest that specific regimens of combined hormone contraceptive use in MRM and migraine with aura may decrease both headache frequency and aura.

Gender influences headache characteristics with increasing age in migraine patients

Background and aims

Migraine headache is one of the most common primary headache disorders and is three times more prevalent in women than in men, especially during the reproductive ages. The neurobiological basis of the female dominance has been partly established. The present study aimed to investigate the effect of gender on the headache manifestations in migraine patients.

Methods

The study group consisted of 2082 adult patients from five different hospitals’ tertiary care-based headache clinics. The relationship between headache characteristics and gender was evaluated in migraine with aura (MwA) and migraine without aura (MwoA). The duration, severity, frequency of headache and associated symptoms were evaluated in both genders and age-dependent variations and analyzed in two subgroups.

Results

Women with migraine were prone to significantly longer duration and intensity of headache attacks. Nausea, phonophobia and photophobia were more prevalent in women. Median headache duration was also longer in women than in men in MwA ( p = 0.013) and MwoA ( p < 0.001). Median headache intensity was higher in women than in men in MwA ( p = 0.010) and MwoA ( p = 0.009). The frequency of nausea was significantly higher in women than in men in MwA ( p = 0.049). Throbbing headache quality and associated features (nausea, photophobia, and phonophobia) were significantly more frequent in women than in men in MwoA. The gender impact varied across age groups and significant changes were seen in female migraineurs after age 30. No age-dependent variation was observed in male migraineurs.

Conclusion

Gender has an influence on the characteristics of the headache as well as on the associated symptoms in migraine patients, and this impact varies across the age groups, particularly in women.

Hormonal contraception in women with migraine: is progestogen-only contraception a better choice?

A significant number of women with migraine has to face the choice of reliable hormonal contraception during their fertile life. Combined hormonal contraceptives (CHCs) may be used in the majority of women with headache and migraine. However, they carry a small, but significant vascular risk, especially in migraine with aura (MA) and, eventually in migraine without aura (MO) with additional risk factors for stroke (smoking, hypertension, diabetes, hyperlipidemia and thrombophilia, age over 35 years). Guidelines recommend progestogen-only contraception as an alternative safer option because it does not seem to be associated with an increased risk of venous thromboembolism (VTE) and ischemic stroke. Potentially, the maintenance of stable estrogen level by the administration of progestins in ovulation inhibiting dosages may have a positive influence of nociceptive threshold in women with migraine. Preliminary evidences based on headache diaries in migraineurs suggest that the progestin-only pill containing desogestrel 75μg has a positive effect on the course of both MA and MO in the majority of women, reducing the number of days with migraine, the number of analgesics and the intensity of associated symptoms. Further prospective trials have to be performed to confirm that progestogen-only contraception may be a better option for the management of both migraine and birth control. Differences between MA and MO should also be taken into account in further studies.

Cortical spreading depression as a target for anti-migraine agents

Spreading depression (SD) is a slowly propagating wave of neuronal and glial depolarization lasting a few minutes, that can develop within the cerebral cortex or other brain areas after electrical, mechanical or chemical depolarizing stimulations. Cortical SD (CSD) is considered the neurophysiological correlate of migraine aura. It is characterized by massive increases in both extracellular K⁺ and glutamate, as well as rises in intracellular Na⁺ and Ca²⁺. These ionic shifts produce slow direct current (DC) potential shifts that can be recorded extracellularly. Moreover, CSD is associated with changes in cortical parenchymal blood flow. CSD has been shown to be a common therapeutic target for currently prescribed migraine prophylactic drugs. Yet, no effects have been observed for the antiepileptic drugs carbamazepine and oxcarbazepine, consistent with their lack of efficacy on migraine. Some molecules of interest for migraine have been tested for their effect on CSD. Specifically, blocking CSD may play an enabling role for novel benzopyran derivative tonabersat in preventing migraine with aura. Additionally, calcitonin gene-related peptide (CGRP) antagonists have been recently reported to inhibit CSD, suggesting the contribution of CGRP receptor activation to the initiation and maintenance of CSD not only at the classic vascular sites, but also at a central neuronal level. Understanding what may be lying behind this contribution, would add further insights into the mechanisms of actions for "gepants", which may be pivotal for the effectiveness of these drugs as anti-migraine agents. CSD models are useful tools for testing current and novel prophylactic drugs, providing knowledge on mechanisms of action relevant for migraine.

Transdermal hormonal therapy in perimenstrual migraine: why, when and how?

Experimental and clinical evidence is strongly in favor of a role for estrogens in migraine. It is clear that estrogen fluctuations represent trigger factors for the attacks, while the resolution of these fluctuations (menopause) may be associated to the remission or, conversely, to the worsening of the disease. However, the exact mechanisms and mediators underlying the effects of estrogens in migraine are largely unknown. The exact mechanisms and mediators underlying the effects of estrogens in migraine are largely unknown. In this review, we summarize clinical and preclinical data that are relevant for the role of estrogens in migraine and we discuss how estrogen modulation can be exploited positively to improve hormonal-related migraine.

Behavioral evidence for photophobia and stress-related ipsilateral head pain in transgenic Cacna1a mutant mice

Migraine is a highly prevalent, disabling and complex episodic brain disorder whose pathogenesis is poorly understood, due in part to the lack of valid animal models. Here we report behavioral evidence of hallmark migraine features, photophobia and unilateral head pain, in transgenic knock-in mice bearing human familial hemiplegic migraine, type 1 (FHM-1) gain-of-function missense mutations (R192Q or S218L) in the Cacna1a gene encoding the CaV2.1 calcium channel α1 subunit. Photophobia was demonstrated using a modified elevated plus maze in which the safe closed arms were brightly illuminated; mutant mice avoided the light despite showing no differences in the standard (anxiety) version of the test. Multiple behavioral measures suggestive of spontaneous head pain were found in 192Q mutants subjected to novelty and/or restraint stress. These behaviors were: (1) more frequent in mutant versus wildtype mice; (2) lateralized in mutant but not in wildtype mice; (3) more frequent in females versus males; and (4) dose-dependently normalized by systemic administration of 2 different acute analgesics, rizatriptan and morphine. Furthermore, some of these behaviors were found to be more frequent and severe in 218L compared to 192Q mutants, consistent with the clinical presentation in humans. We suggest that Cacna1a transgenic mice can experience migraine-related head pain and can thus serve as unique tools to study the pathogenesis of migraine and test novel antimigraine agents.

Her versus his migraine: multiple sex differences in brain function and structure

Migraine is twice as common in females as in males, but the mechanisms behind this difference are still poorly understood. We used high-field magnetic resonance imaging in male and female age-matched interictal (migraine free) migraineurs and matched healthy controls to determine alterations in brain structure. Female migraineurs had thicker posterior insula and precuneus cortices compared with male migraineurs and healthy controls of both sexes. Furthermore, evaluation of functional responses to heat within the migraine groups indicated concurrent functional differences in male and female migraineurs and a sex-specific pattern of functional connectivity of these two regions with the rest of the brain. The results support the notion of a 'sex phenotype' in migraine and indicate that brains are differentially affected by migraine in females compared with males. Furthermore, the results also support the notion that sex differences involve both brain structure as well as functional circuits, in that emotional circuitry compared with sensory processing appears involved to a greater degree in female than male migraineurs.

Mechanisms of G protein-coupled estrogen receptor-mediated spinal nociception

Human and animal studies suggest that estrogens are involved in the processing of nociceptive sensory information and analgesic responses in the central nervous system. Rapid pronociceptive estrogenic effects have been reported, some of which likely involve G protein-coupled estrogen receptor (GPER) activation. Membrane depolarization and increases in cytosolic calcium and reactive oxygen species (ROS) levels are markers of neuronal activation, underlying pain sensitization in the spinal cord. Using behavioral, electrophysiological, and fluorescent imaging studies, we evaluated GPER involvement in spinal nociceptive processing. Intrathecal challenging of mice with the GPER agonist G-1 results in pain-related behaviors. GPER antagonism with G15 reduces the G-1-induced response. Electrophysiological recordings from superficial dorsal horn neurons indicate neuronal membrane depolarization with G-1 application, which is G15 sensitive. In cultured spinal sensory neurons, G-1 increases intracellular calcium concentration and induces mitochondrial and cytosolic ROS accumulation. In the presence of G15, G-1 does not elicit the calcium and ROS responses, confirming specific GPER involvement in this process. Cytosolic calcium concentration elevates faster and with higher amplitude following G-1 intracellular microinjections compared to extracellular exposure, suggesting subcellular GPER functionality. Thus, GPER activation results in spinal nociception, and the downstream mechanisms involve cytosolic calcium increase, ROS accumulation, and neuronal membrane depolarization.

PERSPECTIVE

Our results suggest that GPER modulates pain processing in spinal sensory neurons via cytosolic calcium increase and ROS accumulation. These findings extend the current knowledge on GPER involvement in physiology and disease, providing the first evidence of its pronociceptive effects at central levels and characterizing some of the underlying mechanisms.

Potential role of aromatase over estrogen receptor gene polymorphisms in migraine susceptibility: a case control study from North India

Background

The present study was undertaken to find out the role of estrogen pathway related gene polymorphisms in susceptibility to migraine in Northern Indian population. Aromatase, CYP19A1 (rs10046 and rs4646); estrogen receptors, ESR1 (rs2234693, rs1801132, rs2228480 and rs9340799) and ESR2 (rs1271572 and rs1256049) polymorphisms were selected for the present study.

Methodology/Principal Findings

The patients were recruited in two cohorts – primary (207) and replicative (127) along with 200 healthy controls and genotyped for various polymorphisms. Logistic regression analysis was applied for statistical analyses. The results were validated in the replicative cohort and pooled by meta analysis using Fisher's and Mantel-Haenszel test. Furthermore, Benjamini – Hochberg false discovery rate test was used to correct for multiple comparisons. CYP19A1 rs10046 and CYP19A1 rs4646 polymorphisms were found to confer risk and protective effect, respectively. Out of four ESR1 polymorphisms, only rs2234693 variant allele was significantly associated in migraine with aura. No significant associations were observed for ESR2 polymorphisms. Significant haplotypes were identified for CYP19A1 and ESR1 polymorphisms. Gene- gene interactions of genotypes as well as haplotypes were observed for CYP19A1- ESR1 showing both risk and protective combinations.

Conclusion

We strongly suggest CYP19A1 polymorphisms to be the major contributing factors in migraine susceptibility instead of genetic variants of estrogen receptors.