Differing central amine receptor sensitivity in different migraine subtypes? A neuroendocrine study using buspirone

Prolactin and oxytocin: potential targets for migraine treatment

Migraine is a severe neurovascular disorder of which the pathophysiology is not yet fully understood. Besides the role of inflammatory mediators that interact with the trigeminovascular system, cyclic fluctuations in sex steroid hormones are involved in the sex dimorphism of migraine attacks. In addition, the pituitary-derived hormone prolactin and the hypothalamic neuropeptide oxytocin have been reported to play a modulating role in migraine and contribute to its sex-dependent differences. The current narrative review explores the relationship between these two hormones and the pathophysiology of migraine. We describe the physiological role of prolactin and oxytocin, its relationship to migraine and pain, and potential therapies targeting these hormones or their receptors.In summary, oxytocin and prolactin are involved in nociception in opposite ways. Both operate at peripheral and central levels, however, prolactin has a pronociceptive effect, while oxytocin appears to have an antinociceptive effect. Therefore, migraine treatment targeting prolactin should aim to block its effects using prolactin receptor antagonists or monoclonal antibodies specifically acting at migraine-pain related structures. This action should be local in order to avoid a decrease in prolactin levels throughout the body and associated adverse effects. In contrast, treatment targeting oxytocin should enhance its signalling and antinociceptive effects, for example using intranasal administration of oxytocin, or possibly other oxytocin receptor agonists. Interestingly, the prolactin receptor and oxytocin receptor are co-localized with estrogen receptors as well as calcitonin gene-related peptide and its receptor, providing a positive perspective on the possibilities for an adequate pharmacological treatment of these nociceptive pathways. Nevertheless, many questions remain to be answered. More particularly, there is insufficient data on the role of sex hormones in men and the correct dosing according to sex differences, hormonal changes and comorbidities. The above remains a major challenge for future development.

Evidence for hyperprolactinemia in migraineurs: a systematic review and meta-analysis

BACKGROUND

One of the hypothalamus-pituitary axis hormones which may play a crucial role in pathophysiology of migraine is prolactin which is secreted from anterior pituitary gland and synthesized by various immune system cells as well. Whether prolactin blood levels can affect the migraine pathogenesis is an open question. Therefore, investigating prolactin circulatory levels in migraineurs may pave the way to underpin the mechanisms of migraine pathophysiology at biochemical levels. In the current investigation, the prolactin blood levels in the migraine subjects were investigated using systematic review and meta-analysis.

METHODS

Using online and specialized biomedical databases including Google Scholar, Medline, Pubmed, Pubmed Central, Embase, and Scopus, without the beginning date restriction until Feb 2019, the systematic review retrieved 11 publications in this systematic review after fulfilling for the inclusion and exclusion criteria. For heterogeneity, extent calculation statistical testing was applied. In the present study, the levels of circulatory prolactin in migraineurs assessed using standardized mean difference (SMD) as the effect size.

RESULTS

Q quantity and I²% statistic index showed a high heterogeneity in the 13 selected publications (188.370 and 92.568, respectively) and random-effects model was chosen for further analyses. The meta-analysis on a total number of 460 migraineurs and 429 healthy controls found that the weighted pooled SMD for the effects of prolactin blood concentrations on migraine pathogenesis was as follows: SMD = 1.435 (95% confidence interval, 0.854-2.015).

CONCLUSION

The current investigation presents evidence that prolactin blood levels are higher in migraineurs than healthy subjects.

Gender aspects of the pain syndrome

In recent years, the subject of sex differences in the pain experience attracts a growing interest. The epidemiological and clinical data indicate that women have increased risk of chronic pain, and according to some sources, even experience more intense pain. The hypothetical biological mechanisms underlying sex differences in pain perception consist in the modulating effects produced by sex hormones in relation to the neural substrate. This is confirmed by data on the distribution of gonadal hormones and their receptors in the areas of the peripheral and central nervous system that provide nociceptive transmission. The complexity of the estradiol and progesterone effects on pain sensitivity lies in the fact that, according to various data, both have pre-nociceptive and antinociceptive effects, and testosterone appears to be more characterized by antinociceptive properties. The lion’s share of researches demonstrates the effect of a clinical pain exacerbation during the menstrual cycle. There is irrefutable information about gender differences in responses to drug and non-drug pain treatment, although the results vary depending on a specific therapy and may depend on pain characteristics. Since the recommended dosage of a medication is often based on an “average” male weigh 70 kg, female patients may be facing the risk of increased therapeutic or adverse effects of a drug. The cause is in a higher average percentage of body fat, a lower mean body weight, which contributes to higher median drug concentrations compared with male patients. At present, the available evidence does not allow adapting the methods of pain syndrome treatment to a gender. However, such innovations are quite possible and desirable in the foreseeable future. Additional studies will be required to clarify the mechanisms that determine sex differences in pain responses in order to provide adequate pain relief, according to the patient’s needs.

Prolactin receptor in regulation of neuronal excitability and channels

Prolactin (PRL) activates PRL receptor isoforms to exert regulation of specific neuronal circuitries, and to control numerous physiological and clinically-relevant functions including; maternal behavior, energy balance and food intake, stress and trauma responses, anxiety, neurogenesis, migraine and pain. PRL controls these critical functions by regulating receptor potential thresholds, neuronal excitability and/or neurotransmission efficiency. PRL also influences neuronal functions via activation of certain neurons, resulting in Ca(2+) influx and/or electrical firing with subsequent release of neurotransmitters. Although PRL was identified almost a century ago, very little specific information is known about how PRL regulates neuronal functions. Nevertheless, important initial steps have recently been made including the identification of PRL-induced transient signaling pathways in neurons and the modulation of neuronal transient receptor potential (TRP) and Ca(2+) -dependent K(+) channels by PRL. In this review, we summarize current knowledge and recent progress in understanding the regulation of neuronal excitability and channels by PRL.

Comparing treatments for endometriosis-related pain symptoms in patients with migraine without aura

Endometriosis is a gynecological disorder defined by the presence of endometrial-like tissue outside the uterus. Several studies have found an epidemiological correlation between endometriosis and migraine, probably due to the association of both diseases with female hormones. Progestins or combined oral contraceptives are the first-line medical therapy in women with endometriosis; however, it is well known that in some women the use of combined oral contraceptives could exacerbate migraine. This observation poses a challenge to clinicians who must concomitantly treat endometriosis-related symptoms and migraine. This review summarizes the available literature on the medical treatment of endometriosis in women suffering concomitant migraine without aura until March 2012. Due to the lack of available studies on this topic, it is difficult to draw definitive conclusions. Further studies evaluating hormonal therapies are needed; in particular, progestin therapy should be reconsidered in women with migraine and concomitant endometriosis.

Relationship of female sex hormones with pain perception: focus on estrogens

SUMMARY The role of gonadal hormones has slowly gathered the right attention in the study of chronic pain mechanisms. The clear presence of sex differences in chronic pain and the number of studies showing the power of gonadal hormones to modify pain-induced behavioral responses appear to have convinced clinicians and researchers. Indeed, available data strongly indicate that more studies on gonadal hormones would certainly enhance the possibility of greatly increasing the knowledge of pain mechanisms and, thus, treatments. In the present article, old and new literature are summarized to evaluate data on pain and its modulation by gonadal hormones, particularly estrogens. Peripheral and central targets of these hormones are discussed with the aim of renewing interest in important aspects of estrogenic functions and their interactions with pain processes.

Brainstem changes in 5-HT1A receptor availability during migraine attack

BACKGROUND

Among serotonin receptors, 5-HT(1A) receptors are implicated in the regulation of central serotoninergic tone and could be involved in the abnormal brain 5-HT turnover suspected in migraineurs. The aim of this study was to investigate 5-HT(1A) receptors' availability during migraine attacks.

METHODS

Ten patients suffering from odor-triggered migraine attacks and 10 control subjects were investigated using positron emission tomography (PET) and [(18)F]MPPF PET tracer, a selective 5-HT(1A) antagonist. All subjects underwent calibrated olfactory stimulations prior to the PET study.

RESULTS

Four patients developed a migraine attack during the PET study. In these patients, statistical parametrical mapping and region of interest analyses showed an increased [(18)F]MPPF binding potential (BP(ND)) in the pontine raphe when compared to headache-free migraineurs and control subjects. This ictal change was confirmed at the individual level in each of the four affected patients. In comparison with the headache-free migraineurs, patients with a migraine attack also showed significantly increased [(18)F]MPPF BP(ND) in the left orbitofrontal cortex, precentral gyrus and temporal pole. No significant change in [(18)F]MPPF BP(ND) was observed between headache-free migraineurs and controls.

CONCLUSIONS

Our results emphasize the role of 5HT(1A) receptors in the pontine raphe nuclei during the early stage of migraine attacks.

Ovarian Hormones and Migraine Headache: Understanding Mechanisms and Pathogenesis-Part 2

Migraine headache is strongly influenced by reproductive events that occur throughout the lifespan of women. Each of these reproductive events has a different "hormonal milieu," which might modulate the clinical course of migraine headache. Estrogen and progesterone can be preventative or provocative for migraine headache under different circumstances depending on their absolute serum levels, constancy of exposure, and types of estrogen/progesterone derivatives. Attacks of migraine with and without aura respond differently to changes in ovarian hormones. Clearly a greater knowledge of ovarian hormones and their effect on migraine is essential to a greater understanding of the mechanisms and pathogenesis of migraine headache.