Ovarian steroids regulate neuropeptides in the trigeminal ganglion

Long-term estradiol-17β administration decreases the number of neurons in the caudal mesenteric ganglion innervating the ovary in sexually mature gilts

The effect of estradiol-17β (E(2)) on the number and distribution of neurons in the caudal mesenteric ganglion (CaMG) supplying the ovary of adult pigs was investigated. Also, the numbers of ovarian dopamine-β-hydroxylase (DβH-), neuropeptide Y (NPY-), somatostatin (SOM-), galanin (GAL-) and estrogen receptor (ER)-immunoreactive perikarya as well as the density of the intraganglionic nerve fibers containing DβH and/or NPY, SOM, GAL were determined. E(2) was administered i.m. from day 4 of the first studied estrous cycle to the expected day 20 of the second studied cycle. Injections of E(2) (1) increased the E(2) level in the peripheral blood approximately 4-5 fold, (2) decreased the number of small-sized Fast Blue-positive postganglionic neurons in the CaMG, (3) decreased the number of small perikarya in the ventral, dorsal and central regions of the CaMG, (4) decreased the number of large perikarya in the dorsal and central regions, (5) decreased the number of small and large perikarya in the CaMG that were DβH(+)/NPY(+), (6) decreased the number of small DβH(+) but NPY(-) perikarya, (7) decreased the number of small perikarya coded DβH(+)/SOM(+) and DβH(+)/SOM(-), (8) decreased the number of small DβH(+)/GAL(-) perikarya, (9) decreased the number of small and large perikarya expressing ER subtypes α and β and (10) decreased the total number of nerve fibers in the CaMG containing DβH and/or NPY and DβH and/or GAL. These results show that long-term E(2) treatment of adult gilts downregulates the populations of both noradrenergic and ERs expressing ovarian neurons in the CaMG. Our findings suggest also that elevated E(2) levels that occur during pathological states may regulate gonadal function(s) by affecting ovary supplying neurons.

Distribution and chemical coding of sympathetic neurons in the caudal mesenteric ganglion projecting to the ovary in sexually mature gilts

The distribution and co-localisation patterns of dopamine-beta-hydroxylase (DβH), neuropeptide Y (NPY), somatostatin (SOM) and galanin (GAL) were investigated by use of retrograde neuronal tracing and double-labelling immunofluorescence techniques in the caudal mesenteric ganglion (CaMG) neurons supplying the ovary of adult pigs. The existence and density of nerve fibres that are immunoreactive (IR) for the above-mentioned neuroactive substances were also evaluated. Injections of a fluorescent tracer (Fast Blue; FB) into the ovaries revealed the presence of small- (76.38%) and large-sized (23.62%) FB-positive postganglionic neurons in the CaMG. Noradrenergic FB-positive cells were simultaneously NPY- (43.38%), SOM- (18.77%) and GAL- (18.31%) IR. Of the examined FB-positive neurons, 53.49% were DβH-IR but NPY-immunonegative (IN), 79.06% were DβH-IR but SOM-IN, and 77.16% were DβH-IR but GAL-IN. Small- or large-sized subsets of traced neurons were supplied by only one or a few nerve fibres, exhibiting DβH-, NPY-, SOM- and/or GAL-IR. Our data show the specific morphological as well as immunochemical structural organisation of the sympathetic neurons in the CaMG in adult gilts. The occurrence of an abundant population of noradrenergic perikarya in the CaMG may suggest their important physiological role in the regulation of gonadal function(s) in these animals.

Gonadal hormones decrease temporomandibular joint kappa-mediated antinociception through a down-regulation in the expression of kappa opioid receptors in the trigeminal ganglia

We have previously demonstrated that activation of kappa-opioid receptor located in the temporomandibular joint (TMJ) of rats induces a significantly greater TMJ antinociception in diestrus females than in proestrus females (higher estradiol serum levels than diestrus) and males. These findings indicate that gonadal hormones decrease TMJ kappa-mediated antinociception. The aim of this study was to investigate some of the mechanisms by which gonadal hormones decrease TMJ kappa-mediated antinociception. Western blot analysis demonstrated a significantly lower kappa-opioid receptor expression in the trigeminal ganglia of intact males than in intact and ovariechtomized (OVX) females and orchidectomized (ORX) males. In females, kappa-opioid receptor expression in the trigeminal ganglia was significantly lower in proestrus than in diestrus and OVX females. Taken together these findings suggest that gonadal hormones, especially male gonadal hormones, down-regulate kappa-opioid receptor expression. Co-application of the NOS inhibitor L-NMMA or the NO-sensitive guanylyl cyclase inhibitor ODQ with the kappa-opioid receptor agonist U50,488 blocked TMJ kappa-mediated antinociception in males and females. These findings suggest that antinociception induced by activation of kappa opioid receptors in the TMJ region is mediated by the L-arginine/NO/cGMP pathway in both sexes. Despite the involvement of the L-arginine/NO/cGMP pathway in TMJ kappa-mediated antinociception in both sexes, gonadal hormones do not diminish the activity of this pathway to decrease TMJ kappa-mediated antinociception. Alternatively, they significantly reduce kappa-opioid receptor expression in the trigeminal ganglia.

Altered trigeminal system excitability in menstrual migraine patients

To evaluate brainstem excitability in menstrual migraine (MM) patients and compare the electrophysiological parameters of the trigeminocervical reflex (TCR) during the perimenstrual (headache period) and follicular (headache-free) periods with those in healthy controls. Thirty-one patients with MM and 22 volunteer age- and sex-matched healthy women were included in the study. The TCR was studied bilaterally with stimulation of the supraorbital branch of the trigeminal nerve during the perimenstrual period and follicular phase. The electrophysiological parameters of the TCR were compared between MM patients and controls. In controls, there was no statistically significant difference in the mean reflex latencies recorded during the perimenstrual and follicular phases (P > 0.05). In MM patients, the mean reflex latencies recorded during the perimenstrual (headache period) and follicular phase (headache-free) periods were significantly different from each other and from those in controls. The latencies of MM patients during the follicular (headache-free) period were significantly longer than those of controls. Brainstem excitability differed significantly between the perimenstrual (headache period) and follicular phase (headache-free) periods in MM. Furthermore, trigeminal excitability in MM patients was significantly different from that in healthy controls in both phases of the menstrual period.

Estrogen-growth factor interactions and their contributions to neurological disorders

Estrogen has diverse and powerful effects in the brain, including actions on neurons, glia, and the vasculature. It is not surprising, therefore, that there are many changes in the female brain as serum estradiol levels rise and fall during the normal ovarian cycle. At times of life when estradiol levels change dramatically, such as puberty, postpartum, or menopause, there also are dramatic changes in the central nervous system. Changes that occur because of fluctuations in serum estrogen levels are potentially relevant to neurological disorders because symptoms often vary with the time of the ovarian cycle. Moreover, neurological disorders (eg, seizures and migraine) often increase in frequency in women when estradiol levels change. In this review, the contribution of 2 growth factors targeted by estrogen, the neurotrophin brain-derived neurotrophic factor (BDNF) and vascular endothelial growth factor (VEGF), will be discussed. Estrogen-sensitive response elements are present on the genes for both BDNF and VEGF, and they are potent modulators of neuronal, glial, and vascular function, making them logical candidates to mediate the multitude of effects of estrogen. In addition, BDNF induces neuropeptide Y, which has diverse actions that are relevant to estrogen action and to the same neurological disorders.

The possible role of estrogen in the incidence of temporomandibular disorders

Epidemiologic literatures suggest that temporomandibular joint disorders (TMD) are more prevalent in women than in men. It is affecting approximately 7-15% of the adult population in North America, and 80% of patients treated for TMD are women. The severity of symptoms is also related to the age of the patients. The gender and age distribution of TMD suggests a possible link between its pathogenesis and estrogen. It has been reported that estrogen could influence the development, restitution and metabolism of the temporomandibular joint and associated structures such as bone, cartilage and articular disc. Estrogen can also influence the regulative mechanism of pain. In this article, we will use the hypothesis that the overwhelming majority of patients treated for temporomandibular disorders are women and use the available literature to examine the role of estrogens in TMD.

[Migraine and hormones: what can we be certain of?]

Women suffer from migraine far more frequently than men. This sex difference during the reproductive years is considered to result from additional trigger factors, such as the fluctuating hormones of the menstrual cycle and with the reproductive milestones of women. The role of the female hormones on migraine is illustrated by the phenomenon of menstrual migraine, and the changes in the clinical course of migraine with menarche, pregnancy, menopause and the external application of hormones. In summary, epidemiological, clinical and experimental studies document a substantial influence of female sex hormones on the pathophysiology of migraine headache.

Hormonal changes throughout life in women

The changes in hormonal milieu associated with menarche, pregnancy, lactation, and menopause are frequently accompanied by changes in the patterns and frequency of migraine. Migraine headache is more common in females and, for many women, the onset of this condition occurs at menarche. As many as 60% of women migraineurs report an association between migraine and menstruation, and evidence suggests that estrogen withdrawal may be a trigger for menstrual migraine in susceptible women. Moreover, in the majority of women, migraine frequency increases during the pill-free interval with oral contraceptive use and during the postpartum period, which are other times of decreasing estrogen levels. Migraine frequency tends to decrease during periods of increasing or stable estrogen levels. For these reasons, the numerous neuroendocrine effects elicited by estrogen have been evaluated to explain its role in migraine. Overall, estrogen appears to be a key factor in menstrual migraine, but it is likely to be only one of several factors that act in concert to trigger migraine in susceptible women. Understanding the relationship of the different hormonal milieus through the natural course of women's lives can guide diagnosis and treatment.

The influence of gender and sex steroids on craniofacial nociception

Several pain conditions localized to the craniofacial region show a remarkable sex-related difference in their prevalence. These conditions include temporomandibular disorders and burning mouth syndrome as well as tension-type, migraine, and cluster headaches. The mechanisms that underlie sex-related differences in the prevalence of these craniofacial pain conditions remain obscure and likely involve both physiological and psychosocial factors. In terms of physiological factors relevant to the development of headache, direct evidence of sex-related differences in the properties of dural afferent fibers or durally activated second-order trigeminal sensory neurons has yet to be provided. There is, however, evidence for sex-related differences in the response properties of afferent fibers and second-order trigeminal sensory neurons that convey nociceptive input from other craniofacial tissues associated with sex-related differences in chronic pain conditions, such as those that innervate the masseter muscle and temporomandibular joint. Further, modulation of craniofacial nociceptive input by opioidergic receptor mechanisms appears to be dependent on biological sex. Research into mechanisms that may contribute to sex-related differences in trigeminal nociceptive processing has primarily focused on effect of the female sex hormone estrogen, which appears to alter the excitability of trigeminal afferent fibers and sensory neurons to noxious stimulation of craniofacial tissues. This article discusses current knowledge of potential physiological mechanisms that could contribute to sex-related differences in certain craniofacial pain conditions.

Sex-related differences in NMDA-evoked rat masseter muscle afferent discharge result from estrogen-mediated modulation of peripheral NMDA receptor activity

In the present study, the hypothesis that sex-related differences in glutamate-evoked rat masseter muscle afferent discharge may result from estrogen-related modulation of peripheral N-methyl-d-aspartate (NMDA) receptor activity and/or expression was tested by examining afferent fiber discharge in response to masseter injection of NMDA and the expression of NR2A/B subunits by masseter ganglion neurons in male and female rats. The results showed that injection of NMDA into the masseter muscle evoked discharges in putative mechanonociceptive afferent fibers and increased blood pressure that was concentration-dependent, however, a systemic action of NMDA appeared responsible for increased blood pressure. NMDA-evoked afferent discharge was significantly greater in female than in male rats, was positively correlated with plasma estrogen levels in females and was significantly greater in ovariectomized female rats treated with a high dose (5 mug/day) compared with a low dose (0.5 mug/day) of estrogen. Pre-treatment of high dose estrogen-treated-ovariectomized female rats with the Src tyrosine kinase inhibitor PP2 did not affect NMDA-evoked afferent discharge. NMDA-evoked afferent discharge was attenuated by the antagonists ketamine and ifenprodil, which is selective for NR2B containing NMDA receptors. Fewer masseter ganglion neurons expressed the NR2A (16%) subunit as compared with the NR2B subunit (38%), which was expressed at higher frequencies in intact female (46%) and high dose estrogen-treated ovariectomized female (60%) rats than in male (31%) rats. Taken together, these results suggest that sex-related differences in NMDA-evoked masseter afferent discharge are due, at least in part, to an estrogen-mediated increase in expression of peripheral NMDA receptors by masseter ganglion neurons in female rats.

Management of burning mouth syndrome: systematic review and management recommendations

Primary burning mouth syndrome (BMS) is a chronic, idiopathic intraoral mucosal pain condition that is not accompanied by clinical lesions or systemic disease. There is some uncertainty whether this condition should be referred to as a disease, a disorder, or a syndrome but there are insufficient data to justify any change in taxonomy at present. BMS occurs most often among women and is often accompanied by xerostomia and taste disturbances. More recently a neuropathological basis has been proposed so that BMS may be regarded as an oral dysesthesia or painful neuropathy. However, our incomplete understanding of the epidemiology, etiology, pathophysiology, and lack of diagnostic criteria are barriers to critical investigation and selection of effective treatments. There is only limited evidence to guide clinicians in the management of patients with BMS. Treatable secondary causes should be investigated before diagnosing primary BMS. Topical clonazepam and cognitive therapy have been proven efficacious in some patients. Emerging evidence supports the effectiveness of the antioxidant, alpha lipoic acid, with further studies of this agent being warranted. Additional research into mechanisms, diagnostic criteria, and randomized controlled interventional studies are needed.

Potential role of female sex hormones in the pathophysiology of migraine

Clinical evidence indicates that female sex steroids may contribute to the high prevalence of migraine in women, as well as changes in the frequency or severity of migraine attacks that are in tandem with various reproductive milestones in women's life. While female sex steroids do not seem to be involved in the pathogenesis of migraine per se, they may modulate several mediators and/or receptor systems via both genomic and non-genomic mechanisms; these actions may be perpetuated at the central nervous system, as well as at the peripheral (neuro)vascular level. For example, female sex steroids have been shown to enhance: (i) neuronal excitability by elevating Ca(2+) and decreasing Mg(2+) concentrations, an action that may occur with other mechanisms triggering migraine; (ii) the synthesis and release of nitric oxide (NO) and neuropeptides, such as calcitonin gene-related peptide CGRP, a mechanism that reinforces vasodilatation and activates trigeminal sensory afferents with a subsequent stimulation of pain centres; and (iii) the function of receptors mediating vasodilatation, while the responses of receptors inducing vasoconstriction are attenuated. The serotonergic, adrenergic and gamma-aminobutyric acid (GABA)-ergic systems are also modulated by sex steroids, albeit to a varying degree and with potentially contrasting effects on migraine outcome. Taken together, female sex steroids seem to be involved in an array of components implicated in migraine pathogenesis. Future studies will further delineate the extent and the clinical relevance of each of these mechanisms, and will thus expand the knowledge on the femininity of migraine.

Hormonal Management of Migraine Associated With Menses and the Menopause: A Clinical Review

OBJECTIVE

This article reviews hormonal strategies used to treat headaches attributed to the menstrual cycle or to peri- or postmenopausal estrogen fluctuations. These may occur as a result of natural ovarian cycles, or in response to the withdrawal of exogenously administered estrogen.

BACKGROUND

A wide variety of evidence indicates that cyclic ovarian sex steroid production affects the clinical expression of migraine. This has led to interest in the use of hormonal treatments for migraine.

METHODS

A PubMed search of the literature was conducted using the terms "migraine,""treatment,""estrogen,""hormones,""menopause," and "menstrual migraine." Articles were selected on the basis of relevance.

RESULTS

The overarching goal of hormonal treatment regimens for migraine is minimization of estrogen fluctuations. For migraine associated with the menstrual cycle, supplemental estrogen may be administered in the late luteal phase of the natural menstrual cycle or during the pill-free week of traditional combination oral contraceptives. Modified contraceptive regimens may be used that extend the duration of active hormone use, minimize the duration or extent of hormone withdrawal, or both. In menopause, hormonally associated migraine is most likely to be due to estrogen-replacement regimens, and treatment generally involves manipulating these regimens. Evidence regarding the safety and efficacy of these regimens is limited.

CONCLUSIONS

Hormonal treatment of migraine is not a first-line treatment strategy for most women with migraine. Evidence is lacking regarding its long term harms and migraine is a contraindication to the use of exogenous estrogen in all women with aura and those aged 35 or older. The harm to benefit balances of several traditional nonhormonal therapies are better established.

Capsaicin sensitive neurons role in the inflamed TMJ acute nociceptive response of female and male rats

Computerized meal pattern analysis, and more specifically meal duration, has recently been used as a non-invasive biological marker of nociception in the temporomandibular joint (TMJ). Cells responsible for the nociceptive response in the inflamed TMJ may include capsaicin (CAP) sensitive neurons. To test the role of CAP sensitive neurons in acute nociceptive responses first, male and female rats were treated neonatally with vehicle or CAP, an agent known to destroy a majority of C fibers. Second, after 56 days the rats were divided into four groups: neonatal vehicle-injected and treated with and without complete Freund's adjuvant (CFA). Treatment groups included neonatal non-CAP vehicle treated and TMJ not-injected (CON); vehicle treated and TMJ CFA injected (CFA); CAP-treated and not-injected (CAP); and CAP-treated and CFA injected (CAP+CFA). Meal patterns were analyzed for two days after injection. CFA-injection in non-CAP-treated rats lengthened meal duration on the first and second day after treatment in the males, but only on the first day in the females. CAP treatment in male and female rats prevented significant lengthening of meal duration induced by CFA. CAP treatment attenuated the CFA-induced increase in calcitonin gene-related peptide expression in the trigeminal ganglia similarly in males and females. The data suggests CAP-sensitive neurons are responsible, in part, for transmission of acute nociceptive responses associated with CFA administration and suggest gender can affect nociception in the inflamed TMJ region.

Local blockade of integrins in the temporomandibular joint region reduces Fos-positive neurons in trigeminal subnucleus caudalis of female rats produced by jaw movement

This study assessed the influence of integrins on trigeminal brainstem neural activity evoked during jaw movement (JM). Limited range of motion and pain during jaw opening are common complaints of patients with temporomandibular joint (TMJ) disorders. JM (0.5 Hz, 30 min) was presented to ovariectomized (OvX) female rats given estrogen replacement and males under barbiturate anesthesia. Quantification of Fos-like immunoreactivity (Fos-LI) after JM served as an index of evoked neural activity. Rats were injected locally in the TMJ with either an active (GRGDS, 300 microM, 25 microl) or an inactive integrin antagonist (SDGRG) prior to JM. The effect of prior inflammation of the TMJ region was assessed in separate groups of rats by injecting bradykinin (10 microM, 25 microl) with or without integrin drugs prior to JM. Active integrin antagonist significantly reduced JM-evoked Fos-LI in superficial laminae at the trigeminal subnucleus caudalis/upper cervical cord (Vc/C2) junction in OvX compared to male rats independent of bradykinin pretreatment. Fos-LI produced in the dorsal paratrigeminal and trigeminal subnucleus interpolaris/caudalis (Vi/Vc) transition regions was not reduced by active integrin antagonist in males or OvX females. Active integrin antagonist did not affect Fos-LI produced after injection of bradykinin alone into the TMJ. These results suggest that RGD binding integrins contribute to JM-evoked neural activity at the Vc/C2 junction under naive and inflamed conditions in a sex-dependent manner.

Menstrual Migraine: Pathophysiology, Diagnosis, and Impact

The incidence of migraine varies over the course of the menstrual cycle. In the general population, approximately 60% of women with migraine report an increased frequency of headache during menses. The estrogen withdrawal that occurs just prior to the onset of menses and that leads to loss of serotonergic tone is thought to be the trigger for headaches that arise at this time of the menstrual cycle. The ability of triptans, specific serotonin receptor agonists, to prevent menstrual migraine is consistent with this hypothesis. Moreover, compared with headaches that occur during other times in the cycle, menstrual migraines are more severe in most women and may be of longer duration, as well as more resistant to treatment in a subset of women.

Effects of subcutaneous administration of glutamate on pain, sensitization and vasomotor responses in healthy men and women

The present study aimed to investigate if (1) subcutaneous injection of glutamate induces pain, sensitization and vasomotor responses in humans and (2) if sex differences exist in these responses. Thirty healthy volunteers (men-15 and women-15) were included. Each subject received four subcutaneous injections (0.1ml; glutamate 100, 10, 1mM and isotonic saline 0.9%) into the forehead skin in two sessions separated by one week. Assessments of pain intensity (VAS), quality, distribution; area of pinprick hyperalgesia; pressure pain threshold (PPT) at the injection site; surface skin temperature and local blood flow were performed at predetermined time points. The highest concentration of glutamate evoked the highest pain intensity, the longest duration of pain and the largest pain area under the VAS-time curve (P<0.001) in both men and women, although responses in women were larger than in men (P<0.05). The face-chart pain area was the largest for the highest concentration of glutamate (P<0.001) and women drew a larger pain area than men (P=0.024). The area of pinprick hyperalgesia was the largest for glutamate 100mM (P<0.001) and women indicated a larger area than men (P<0.001). Concentration-dependent local vasomotor responses were found following the subcutaneous injection of glutamate but there was no sex difference in this effect. Glutamate 100mM significantly reduced the PPT values (P<0.001) without sex-related differences. The present study demonstrates for the first time that subcutaneous injection of glutamate evokes pain, vasomotor responses and pinprick hyperalgesia in human volunteers and that there are sex-related differences in some of these responses.

Altered expression of pro-inflammatory and developmental genes in the fetal brain in a mouse model of maternal infection

Human studies of unexplained cerebral palsy (CP) suggest an association with maternal infection. We used an established model of maternal infection, lipopolysaccharide (LPS) administration, to investigate the molecular changes in the fetal brain that may link maternal infection and CP. We compared gene expression in brains from mouse pups exposed to LPS in utero to those from saline-treated controls. Dams were injected with 50 microg LPS or saline on E18 with surgical delivery from 0.5 to 6h later. Differential gene expression was analyzed in the whole mouse brain using RT-PCR. When compared to control mice, pups exposed to LPS showed increased expression of pro-inflammatory genes monocyte chemoattractant protein-1 (MCP-1), interleukin-6 (IL-6), and interleukin-1beta (IL-1beta), as well as VEGF, a regulator of vascular development and permeability, the anti-apoptotic protein Y-box-binding protein-1 (YB-1), and the neuronal differentiation factor necdin. LPS-exposed mice also showed downregulation of semaphorin 5b and groucho, involved in axon guidance and neurogenesis, respectively, providing evidence that LPS may disrupt normal developmental pathways. These data suggest possible mechanisms for adverse neurological outcomes following maternal infection involving elevated cytokine levels and altered expression of developmental genes in the fetal brain.

Ghrelin is expressed in trigeminal neurons of female mice in phase with the estrous cycle

Several disorders mediated by the trigeminal nerve including migraine and temporomandibular disorder (TMD) are more common in women than in men, and painful attacks are often linked to the menstrual cycle. Estrogen receptors in trigeminal neurons may be involved in regulating neuronal function, causing changes in sensitivity that contribute to these attacks. In a previous study, we demonstrated that expression of specific neuropeptides including galanin and neuropeptide Y in trigeminal ganglia of female rodents varies with the estrous cycle. In this study, we examined expression of the orexigenic peptide ghrelin in trigeminal ganglia of cycling female mice. RT-PCR studies demonstrated that ghrelin mRNA is upregulated by over 5-fold at the high estrogen stages of the cycle, proestrus and early estrus over the levels expressed at the low estrogen stage of the cycle, diestrus. Double-labeling immunohistochemical studies and cell size measurements were conducted to identify the phenotype of neurons in trigeminal ganglia containing ghrelin. Ghrelin was present in trigeminal neurons containing peripherin, a marker of neurons with unmyelinated axons, in trigeminal neurons binding IB4, a marker of nonpeptidergic nociceptors, in trigeminal neurons containing neurofilament H, a marker of neurons with myelinated axons, and in trigeminal neurons containing the neuropeptide calcitonin gene-related peptide (CGRP). Ghrelin-positive neurons averaged 25.6 microm in diameter, but included neurons in all the size ranges except the smallest peripherin-positive neurons. Thus, nearly all of the major populations of trigeminal neurons including peptidergic and nonpeptidergic nociceptors contain ghrelin. These studies suggest that ghrelin, a multifunctional peptide, may contribute to the mechanism linking orofacial pain syndromes in females, including temporomandibular disorder and migraine, to cyclical hormonal changes.