Variations in the cannabinoid receptor 1 gene predispose to migraine

In silico analyses of the involvement of GPR55, CB1R and TRPV1: response to THC, contribution to temporal lobe epilepsy, structural modeling and updated evolution

Introduction

The endocannabinoid (eCB) system is named after the discovery that endogenous cannabinoids bind to the same receptors as the phytochemical compounds found in Cannabis. While endogenous cannabinoids include anandamide (AEA) and 2-arachidonoylglycerol (2-AG), exogenous phytocannabinoids include Δ-9 tetrahydrocannabinol (THC) and cannabidiol (CBD). These compounds finely tune neurotransmission following synapse activation, via retrograde signaling that activates cannabinoid receptor 1 (CB1R) and/or transient receptor potential cation channel subfamily V member 1 (TRPV1). Recently, the eCB system has been linked to several neurological diseases, such as neuro-ocular abnormalities, pain insensitivity, migraine, epilepsy, addiction and neurodevelopmental disorders. In the current study, we aim to: (i) highlight a potential link between the eCB system and neurological disorders, (ii) assess if THC exposure alters the expression of eCB-related genes, and (iii) identify evolutionary-conserved residues in CB1R or TRPV1 in light of their function.

Methods

To address this, we used several bioinformatic approaches, such as transcriptomic (Gene Expression Omnibus), protein-protein (STRING), phylogenic (BLASTP, MEGA) and structural (Phyre2, AutoDock, Vina, PyMol) analyzes.

Results

Using RNA sequencing datasets, we did not observe any dysregulation of eCB-related transcripts in major depressive disorders, bipolar disorder or schizophrenia in the anterior cingulate cortex, nucleus accumbens or dorsolateral striatum. Following in vivo THC exposure in adolescent mice, GPR55 was significantly upregulated in neurons from the ventral tegmental area, while other transcripts involved in the eCB system were not affected by THC exposure. Our results also suggest that THC likely induces neuroinflammation following in vitro application on mice microglia. Significant downregulation of TPRV1 occurred in the hippocampi of mice in which a model of temporal lobe epilepsy was induced, confirming previous observations. In addition, several transcriptomic dysregulations were observed in neurons of both epileptic mice and humans, which included transcripts involved in neuronal death. When scanning known interactions for transcripts involved in the eCB system (n = 12), we observed branching between the eCB system and neurophysiology, including proteins involved in the dopaminergic system. Our protein phylogenic analyzes revealed that CB1R forms a clade with CB2R, which is distinct from related paralogues such as sphingosine-1-phosphate, receptors, lysophosphatidic acid receptors and melanocortin receptors. As expected, several conserved residues were identified, which are crucial for CB1R receptor function. The anandamide-binding pocket seems to have appeared later in evolution. Similar results were observed for TRPV1, with conserved residues involved in receptor activation.

Conclusion

The current study found that GPR55 is upregulated in neurons following THC exposure, while TRPV1 is downregulated in temporal lobe epilepsy. Caution is advised when interpreting the present results, as we have employed secondary analyzes. Common ancestors for CB1R and TRPV1 diverged from jawless vertebrates during the late Ordovician, 450 million years ago. Conserved residues are identified, which mediate crucial receptor functions.

Peripheral Endocannabinoid Components and Lipid Plasma Levels in Patients with Resistant Migraine and Co-Morbid Personality and Psychological Disorders: A Cross-Sectional Study

Resistant migraine characterizes those patients who have failed at least three classes of migraine prophylaxis. These difficult-to-treat patients are likely to be characterized by a high prevalence of psychological disturbances. A dysfunction of the endocannabinoid system (ECS), including alteration in the levels of endocannabinoid congeners, may underlie several psychiatric disorders and the pathogenesis of migraines. Here we explored whether the peripheral gene expression of major components of the ECS and the plasma levels of endocannabinoids and related lipids are associated with psychological disorders in resistant migraine. Fifty-one patients (age = 46.0 ± 11.7) with resistant migraine received a comprehensive psychological evaluation according to the DSM-5 criteria. Among the patients, 61% had personality disorders (PD) and 61% had mood disorders (MD). Several associations were found between these psychological disorders and peripheral ECS alterations. Lower plasma levels of palmitoiletanolamide (PEA) were found in the PD group compared with the non-PD group. The MD group was characterized by lower mRNA levels of diacylglycerol lipase α (DAGLα) and CB2 (cannabinoid-2) receptor. The results suggest the existence of peripheral dysfunction in some components of the ECS and an alteration in plasma levels of PEA in patients with resistant migraine and mood or personality disorders.

The Exploration of Cannabis and Cannabinoid Therapies for Migraine

PURPOSE OF REVIEW

There is increasing interest in the use of cannabis and cannabinoid therapies (CCT) by the general population and among people with headache disorders, which results in a need for healthcare professionals to be well versed with the efficacy and safety data. In this manuscript, we review cannabis and cannabinoid terminology, the endocannabinoid system and its role in the central nervous system (CNS), the data on efficacy, safety, tolerability, and potential pitfalls associated with use in people with migraine and headache disorders. We also propose possible mechanisms of action in headache disorders and debunk commonly held myths about its use.

RECENT FINDINGS

Preliminary studies show that CCT have evidence for the management of migraine. While this evidence exists, further randomized, controlled studies are needed to better support its clinical use. CCT can be considered an integrative treatment added to mainstream medicine for people with migraine who are refractory to treatment and/or exhibit disability and/or interest in trying these therapies. Further studies are warranted to specify appropriate formulation, dosage, and indication(s). Although not included in guidelines or the AHS 2021 Consensus Statement on migraine therapies, with the legalization of CCT for medical or unrestricted use across the USA, recent systematic reviews highlighting the preliminary evidence for its use in migraine, it is vital for clinicians to be well versed in the efficacy, safety, and clinical considerations for their use. This review provides information which can help people with migraine and clinicians who care for them make mutual, well-informed decisions on the use of cannabis and cannabinoid therapies for migraine based on the existing data.

Endocannabinergic modulation of central serotonergic activity in healthy human volunteers

BACKGROUND

The serotonergic and the endocannabinoid system are involved in the etiology of depression. Depressive patients exhibit low serotonergic activity and decreased level of the endocannabinoids anandamide (AEA) and 2-arachidonylglycerol (2AG). Since the cannabinoid (CB) 1 receptor is activated by endogenous ligands such as AEA and 2AG, whose concentration are controlled by the fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase, respectively, we investigated the effects on serotonergic utilization. In this study, we investigated the impact of the rs1049353 single-nucleotide polymorphism (SNP) of the cannabinoid receptor 1 (CNR1) gene, which codes the endocannabinoid CB1 receptor, and the rs324420 SNP of the FAAH gene on the serotonergic and endocannabinoid system in 59 healthy volunteers.

METHODS

Serotonergic activity was measured by loudness dependence of auditory-evoked potentials (LDAEP). Plasma concentrations of AEA, 2AG and its inactive isomer 1AG were determined by mass spectrometry. Genotyping of two SNPs (rs1049353, rs344420) was conducted by polymerase chain reaction (PCR) and differential enzymatic analysis with the PCR restriction fragment length polymorphism method.

RESULTS

Genotype distributions by serotonergic activity or endocannabinoid concentration showed no differences. However, after detailed consideration of the CNR1-A-allele-carriers, a reduced AEA (A-allele-carrier M = 0.66, SD = 0.24; GG genotype M = 0.72, SD = 0.24) and 2AG (A-allele-carriers M = 0.70, SD = 0.33; GG genotype M = 1.03, SD = 0.83) plasma concentration and an association between the serotonergic activity and the concentrations of AEA and 2AG has been observed.

CONCLUSIONS

Our results suggest that carriers of the CNR1-A allele may be more susceptible to developing depression.

Exploring Novel Therapeutic Targets in the Common Pathogenic Factors in Migraine and Neuropathic Pain

Migraine and neuropathic pain (NP) are both painful, disabling, chronic conditions which exhibit some symptom similarities and are thus considered to share a common etiology. The calcitonin gene-related peptide (CGRP) has gained credit as a target for migraine management; nevertheless, the efficacy and the applicability of CGRP modifiers warrant the search for more effective therapeutic targets for pain management. This scoping review focuses on human studies of common pathogenic factors in migraine and NP, with reference to available preclinical evidence to explore potential novel therapeutic targets. CGRP inhibitors and monoclonal antibodies alleviate inflammation in the meninges; targeting transient receptor potential (TRP) ion channels may help prevent the release of nociceptive substances, and modifying the endocannabinoid system may open a path toward discovery of novel analgesics. There may exist a potential target in the tryptophan-kynurenine (KYN) metabolic system, which is closely linked to glutamate-induced hyperexcitability; alleviating neuroinflammation may complement a pain-relieving armamentarium, and modifying microglial excitation, which is observed in both conditions, may be a possible approach. Those are several potential analgesic targets which deserve to be explored in search of novel analgesics; however, much evidence remains missing. This review highlights the need for more studies on CGRP modifiers for subtypes, the discovery of TRP and endocannabinoid modulators, knowledge of the status of KYN metabolites, the consensus on cytokines and sampling, and biomarkers for microglial function, in search of innovative pain management methods for migraine and NP.

Potential effects of cannabinoids on audiovestibular function: A narrative review

The growing interest in the development of drugs that target the endocannabinoid system has extended to conditions that affect the audiovestibular pathway. The expression of cannabinoid (CB) receptors in that pathway has been widely demonstrated, indicating a therapeutic potential for drug development at this level. These medications may be beneficial for conditions such as noise-induced hearing loss, ototoxicity, or various forms of vertigo of central or peripheral origin. The therapeutic targets of interest include natural or synthetic compounds that act as CB1/CB2 receptor agonists/antagonists, and inhibitors of the endocannabinoid-degrading enzymes FAAH and MAGL. Furthermore, genetic variations implicated in the response to treatment and the development of related disorders such as epilepsy or migraine have been identified. Direct methods of administering these medications should be examined beyond the systemic strategy.

Cannabinoids and the endocannabinoid system in fibromyalgia: A review of preclinical and clinical research

Characterised by chronic widespread musculoskeletal pain, generalised hyperalgesia, and psychological distress, fibromyalgia (FM) is a significant unmet clinical need. The endogenous cannabinoid system plays an important role in modulating both pain and the stress response. Here, we appraise the evidence, from preclinical and clinical studies, for a role of the endocannabinoid system in FM and the therapeutic potential of targeting the endocannabinoid system. While many animal models have been used to study FM, the reserpine-induced myalgia model has emerged as perhaps the most translatable to the clinical phenotype. Inhibition of fatty acid amide hydrolase (FAAH) has shown promise in preclinical studies, ameliorating pain- and anxiety-related behaviour . Clinically, there is evidence for alterations in the endocannabinoid system in patients with FM, including single nucleotide polymorphisms and increased levels of circulating endocannabinoids and related N-acylethanolamines. Single entity cannabinoids, cannabis, and cannabis-based medicines in patients with FM show promise therapeutically but limitations in methodology and lack of longitudinal studies to assess efficacy and tolerability preclude the current recommendation for their use in patients with FM. Gaps in the literature that warrant further investigation are discussed, particularly the need for further development of animal models with high validity for the multifaceted nature of FM, balanced studies to eliminate sex-bias in preclinical research, and ultimately, better translation between preclinical and clinical research.

The endocannabinoid system and related lipids as potential targets for the treatment of migraine-related pain

BACKGROUND

Migraine is a complex and highly disabling neurological disease whose treatment remains challenging in many patients, even after the recent advent of the first specific-preventive drugs, namely monoclonal antibodies that target calcitonin gene-related peptide. For this reason, headache researchers are actively searching for new therapeutic targets. Cannabis has been proposed for migraine treatment, but controlled clinical studies are lacking. A major advance in cannabinoid research has been the discovery of the endocannabinoid system (ECS), which consists of receptors CB1 and CB2; their endogenous ligands, such as N-arachidonoylethanolamine; and the enzymes that catalyze endocannabinoid biosynthesis or degradation. Preclinical and clinical findings suggest a possible role for endocannabinoids and related lipids, such as palmitoylethanolamide (PEA), in migraine-related pain treatment. In animal models of migraine-related pain, endocannabinoid tone modulation via inhibition of endocannabinoid-catabolizing enzymes has been a particular focus of research.

METHODS

To conduct a narrative review of available data on the possible effects of cannabis, endocannabinoids, and other lipids in migraine-related pain, relevant key words were used to search the PubMed/MEDLINE database for basic and clinical studies.

RESULTS

Endocannabinoids and PEA seem to reduce trigeminal nociception by interacting with many pathways associated with migraine, suggesting a potential synergistic or similar effect.

CONCLUSIONS

Modulation of the metabolic pathways of the ECS may be a basis for new migraine treatments. The multiplicity of options and the wealth of data already obtained in animal models underscore the importance of further advancing research in this area. Multiple molecules related to the ECS or to allosteric modulation of CB1 receptors have emerged as potential therapeutic targets in migraine-related pain. The complexity of the ECS calls for accurate biochemical and pharmacological characterization of any new compounds undergoing testing and development.

A replication study separates polymorphisms behind migraine with and without depression

The largest migraine genome-wide association study identified 38 candidate loci. In this study we assessed whether these results replicate on a gene level in our European cohort and whether effects are altered by lifetime depression. We tested SNPs of the loci and their vicinity with or without interaction with depression in regression models. Advanced analysis methods such as Bayesian relevance analysis and a neural network based classifier were used to confirm findings. Main effects were found for rs2455107 of PRDM16 (OR = 1.304, p = 0.007) and five intergenic polymorphisms in 1p31.1 region: two of them showed risk effect (OR = 1.277, p = 0.003 for both rs11209657 and rs6686879), while the other three variants were protective factors (OR = 0.4956, p = 0.006 for both rs12090642 and rs72948266; OR = 0.4756, p = 0.005 for rs77864828). Additionally, 26 polymorphisms within ADGRL2, 2 in REST, 1 in HPSE2 and 33 mostly intergenic SNPs from 1p31.1 showed interaction effects. Among clumped results representing these significant regions, only rs11163394 of ADGRL2 showed a protective effect (OR = 0.607, p = 0.002), all other variants were risk factors (rs1043215 of REST with the strongest effect: OR = 6.596, p = 0.003). Bayesian relevance analysis confirmed the relevance of intergenic rs6660757 and rs12128399 (p31.1), rs1043215 (REST), rs1889974 (HPSE2) and rs11163394 (ADGRL2) from depression interaction results, and the moderate relevance of rs77864828 and rs2455107 of PRDM16 from main effect analysis. Both main and interaction effect SNPs could enhance predictive power with the neural network based classifier. In summary, we replicated p31.1, PRDM16, REST, HPSE2 and ADGRL2 genes with classic genetic and advanced analysis methods. While the p31.1 region and PRDM16 are worthy of further investigations in migraine in general, REST, HPSE2 and ADGRL2 may be prime candidates behind migraine pathophysiology in patients with comorbid depression.

Diagnostic Challenges and Management of Fibromyalgia

The World Health Organization regards chronic pain to be a public health concern. In clinical medicine, fibromyalgia (FM) is the most prevalent chronic widespread pain disease. In terms of impairment, consumption of health and social resources, and impact on primary and speciality care systems, it has reached worrisome proportions. This disease is frequently managed by primary care providers. Because of its intricacy, fibromyalgia diagnosis and treatment can be difficult. Fibromyalgia is a controversial condition. It might appear ill-defined in comparison to other pain conditions, with no clear knowledge of pathophysiology and hence no particular targeted therapy. This invariably sparks debates and challenges. There is no obvious cut-off point that distinguishes FM from non-FM. The diagnosis of fibromyalgia has been complicated by several factors, including patients' health-seeking behaviour, symptom identification, and physician labelling of the disease. Fibromyalgia is currently considered a centralized pain condition, according to research that has improved our understanding of its etiopathology. A multidisciplinary strategy combining pharmacological and non-pharmacological therapies based on a biopsychosocial paradigm can result in effective therapy. Cultural and psychosocial variables appear to be a recent development in fibromyalgia, and they appear to have a larger influence on physician diagnosis than severe symptom levels in FM patients. Although physicians rely on FM criteria as the only way to classify FM patients in research and clinical settings, some crucial elements of the diagnostic challenge of fibromyalgia remain unsolved - invalidation, psychosocial variables, and diverse illness manifestation are some examples. Beyond the existing constructional scores, physicians' judgment gained in real communicative contexts with patients, appears to be the only dependable route for a more accurate diagnosis for fibromyalgia. We have performed an exhaustive review of the literature using the keywords "Fibromyalgia", "challenges" and "diagnosis" in PubMed and Google Scholar indexes up to September 2021. This article aims to examine the causes, diagnosis, and current treatment protocols of FM, as well as discuss some continuing debates and diagnostic challenges which physicians face in accurately diagnosing fibromyalgia.

A patient perspective of complementary and integrative medicine (CIM) for migraine treatment: a social media survey

Abstract

To survey persons with migraine who use social media about Complementary and Integrative Medicine (CIM) for the treatment of migraine.

Background

CIM encompasses medical treatments that are not part of but are used in concert with mainstream medicine. Between 28 and 82% of people with migraine use non-drug approaches, and approximately 50% of people with migraine do not discuss non-drug treatments with their healthcare providers (HCPs). It is important for providers to be conversant with CIM treatments and the available evidence-based data. To further this effort, people with migraine were surveyed directly through social media to identify CIM practices in which they engage.

Methods

In collaboration with the American Migraine foundation (AMF) and Yakkety Yak, a digital marketing agency, we conducted a cross-sectional survey study. Participants were recruited from the Move Against Migraine (MAM) Facebook group which has 20,000+ members. The goals of the survey were to assess the attitudes toward CIM among this group, to identify which CIM modalities are being used and to determine what patients considered to be the most effective CIM modalities. While Yakkety Yak posted the survey link on the group page, the survey itself was hosted on Qualtrics, a confidential survey service.

Results

372 MAM members (approximately 2%) responded to the questionnaire, of which 335 reported using CIM; between 114 and 139 (34–42%) found CIM modalities to be at least mildly effective. Of note, 164 (49%) reported using cannabis derivatives or cannabinoids, specifically with, 64/164 (39%) reporting that cannabis was not effective for them.

Conclusions

This study provides an initial investigation into the demographic and practice patterns of migraine patients who use CIM. While this sampling may not reflect CIM use across all individuals with migraine, it does strongly suggest the need for better education on the role of, and evidence for, CIM among headache care providers, and the need to ask patients specifically about their use of and interest in CIM.

Cannabis hyperemesis syndrome: an update on the pathophysiology and management

Cannabis hyperemesis syndrome (CHS) is a form of functional gut-brain axis disorder characterized by bouts of episodic nausea and vomiting worsened by cannabis intake. It is considered as a variant of cyclical vomiting syndrome seen in cannabis users especially characterized by compulsive hot bathing/showers to relieve the symptoms. CHS was reported for the first time in 2004, and since then, an increasing number of cases have been reported. With cannabis use increasing throughout the world as the threshold for legalization becomes lower, its user numbers are expected to rise over time. Despite this trend, a strict criterion for the diagnosis of CHS is lacking. Early recognition of CHS is essential to prevent complications related to severe volume depletion. The recent body of research recognizes that patients with CHS impose a burden on the healthcare systems. Understanding the pathophysiology of the endocannabinoid system (ECS) remains central in explaining the clinical features and potential drug targets for the treatment of CHS. The frequency and prevalence of CHS change in accordance with the doses of tetrahydrocannabinol and other cannabinoids in various formulations of cannabis. CHS is unique in presentation, because of the cannabis’s biphasic effect as anti-emetic at low doses and pro-emetic at higher doses, and the association with pathological hot water bathing. In this narrative review, we elaborate on the role of the ECS, its management, and the identification of gaps in our current knowledge of CHS to further enhance its understanding in the future.

Association of a Variant of CNR1 Gene Encoding Cannabinoid Receptor 1 With Gilles de la Tourette Syndrome

Background

Gilles de la Tourette syndrome (GTS) is a neuropsychiatric disorder of unknown etiology, although a major role of genetic factors has been established. Cannabis-based medicines may alleviate GTS-associated tics and variants of CNR1 gene encoding central cannabinoid receptor (CB1) are believed to be a risk factor for the development of some neurodevelopmental diseases. Our aim was to test the association of selected CNR1 gene variants with GTS.

Material and Methods

The cohort of GTS cases comprised 262 unrelated patients aged 3–53 years (mean age: 18.3 ± 9.1 years; 204 males (77.9%), 126 (48.1%) adults defined as ≥18 years). As a control group we enrolled 279 unrelated, ethnically and gender matched individuals with no diagnosed mental, neurological or general disorder, aged 13–54 years (mean age: 22.5 ± 3.0 years; 200 males, (74.1%). Both study and control groups were selected from Polish population, which is ethnically homogenous subgroup of Caucasian population. Four single nucleotide polymorphisms (SNPs) in CNR1 were selected: rs2023239, rs2180619, rs806379, and rs1049353 based on minor allele frequency in general population >15%. These variants were genotyped using a real-time quantitative polymerase chain reaction system (TaqMan SNP genotyping assay).

Results

We found significant association of GTS clinical phenotype with rs2023239 variant. Minor allele C and CT+CC genotypes were found significantly more often in GTS patients compared to controls (17.4 vs 11.1%, p=0.003 and 32.8 vs 20.4%, p=0.001, respectively), and the difference remained significant after correction for multiple testing. C allele of rs2023239 polymorphism of the CNR1 gene was associated with the occurrence of tics. There were no statistically significant associations for rs806379, rs1049353 or rs2180619 variants.

Conclusion

Our findings suggest that C allele of rs2023239 polymorphism of the CNR1 gene is a risk factor of GTS in Polish population. The variant can be potentially associated with abnormal endocannabinoid transmission, which is suspected to be one of the causes of GTS.

The exploration of mechanisms of comorbidity between migraine and depression

Migraine comorbid with depression is common and is often encountered in clinical practice. The comorbidity may lead to more serious conditions with other symptoms and a longer duration of treatment and it may impose heavy economic and social burdens, directly or indirectly, on patients and their families. Numerous studies have been published on the association of migraine with depression. Numerous literature have showed that the comorbidity may have a common complicated pathogenic mechanism involving biopsychosocial characteristics, including abnormal brain development and shared genetic basis, as well as neurotransmitters, sex hormones and stress. In addition, some studies have identified the multiple, bidirectional relationship between migraine and depressive disorder. We searched the literature for the possible common mechanisms between migraine and depression and classified the research results.

Phytomedicines in the Treatment of Migraine

Migraine is a disabling neurovascular disorder with few targeted, tolerable and effective treatments. Phytomedicines, or plant-based medicinal formulations, hold great promise in the identification of novel therapeutic targets in migraine. Many patients also turn toward herbal and plant-based therapies for the treatment of their migraines as clinical and preclinical evidence of efficacy increases. Patients seek effective and tolerable treatments instead of or in addition to current conventional pharmacologic therapies. We review some phytomedicines potentially useful for migraine treatment-feverfew (Tanacetum parthenium), butterbur (Petasites hybridus), marijuana (Cannabis spp.), Saint John's Wort (Hypericum perforatum) and the Damask rose (Rosa × damascena)-with respect to their mechanisms of action and evidence for treatment of migraine. The evidence for feverfew is mixed; butterbur is effective with potential risks of hepatotoxicity related to preparation; marijuana has not been shown to be effective in migraine treatment, and data are scant; Saint John's Wort shows relevant physiological activity but is a hepatic enzyme inducer and lacks clinical studies for this purpose; the Damask rose when used in topical preparations did not show efficacy in one clinical trial. Other plant preparations have been considered for migraine treatment but most without blinded randomized, placebo-controlled trial evidence.

Fibromyalgia: Genetics and epigenetics insights may provide the basis for the development of diagnostic biomarkers

Fibromyalgia is a disease characterized by chronic widespread pain with additional symptoms, such as joint stiffness, fatigue, sleep disturbance, cognitive dysfunction, and depression. Currently, fibromyalgia diagnosis is based exclusively on a comprehensive clinical assessment, according to 2016 ACR criteria, but validated biological biomarkers associated with fibromyalgia have not yet been identified. Genome-wide association studies investigated genes potentially involved in fibromyalgia pathogenesis highlighting that genetic factors are possibly responsible for up to 50% of the disease susceptibility. Potential candidate genes found associated to fibromyalgia are SLC64A4, TRPV2, MYT1L, and NRXN3. Furthermore, a gene-environmental interaction has been proposed as triggering mechanism, through epigenetic alterations: In particular, fibromyalgia appears to be characterized by a hypomethylated DNA pattern, in genes implicated in stress response, DNA repair, autonomic system response, and subcortical neuronal abnormalities. Differences in the genome-wide expression profile of microRNAs were found among multiple tissues, indicating the involvement of distinct processes in fibromyalgia pathogenesis. Further studies should be dedicated to strength these preliminary findings, in larger multicenter cohorts, to identify reliable directions for biomarker research and clinical practice.

Antagonism of Cannabinoid Receptor 1 Attenuates the Anti-Inflammatory Effects of Electroacupuncture in a Rodent Model of Migraine

Background

The anti-nociceptive effects of electroacupuncture (EA) in migraine have been documented in multiple randomised controlled trials. Neurogenic inflammation plays a key role in migraine attacks, and the anti-inflammatory effects of acupuncture have been associated with the type 1 cannabinoid (CB1) receptor.

Objective

To investigate whether CB1 receptors mediate the anti-inflammatory effects of EA on migraine attacks.

Methods

A migraine model was produced in Sprague-Dawley rats by unilateral electrical stimulation of the trigeminal ganglion (TGES). Rats received EA daily on the 5 days preceding TGES with (TGES+EA+SR141716 group) or without (TGES+EA group) intraperitoneal injections of the CB1 receptor antagonist SR141716. Another group of TGES rats (TGES+MA group) and a non-TGES sham-operated group of rats (Sham+MA group) received minimal acupuncture (MA). Calcitonin gene-related peptide (CGRP) and prostaglandin E2 (PGE2) concentrations were determined in serum obtained from the ipsilateral jugular vein at initiation of TGES and 5 min after. Postmortem interleukin (IL)-1β and cyclooxygenase (COX)2 protein levels in the trigeminal ganglion (TG) and plasma protein extravasation (PPE) in the dura mater were assessed.

Results

TGES induced increases in serum CGRP and PGE2 levels (TGES+MA vs baseline and vs Sham: all p<0.001), as well as IL-1β and COX2 protein expression in the TG, and neurogenic PPE levels (TGES+MA vs Sham+MA: all p<0.001). EA attenuated TGES-induced increases in the levels of these proteins (TGES+EA vs TGES+MA: all p<0.001). CB1 receptor antagonism reversed the effects of EA (TGES+EA+SR141716 vs TGES+EA: all p<0.05).

Conclusions

CB1 receptors appear to mediate anti-inflammatory effects of EA in a rat model of migraine.

Emerging drugs for migraine treatment: an update

Introduction: Migraine is a very frequent and disabling neurological disorder. The current treatment options are old, generally poorly tolerated and not migraine-specific, reflecting the low priority of migraine research and highlighting the vast unmet need in its management. Areas covered: Advancement in the understanding of migraine pathophysiological mechanisms and identification of novel potentially meaningful targets have resulted in a multitude of emerging acute and preventive treatments. Here we review the known putative migraine pathophysiological mechanisms in order to understand the rationale of the most promising novel treatments targeting the Calcitonin-Gene-Related Peptide receptor and ligand and the 5 hydroxytryptamine (5-HT)1F receptor. Key findings on the phase II and phase III clinical trials on these treatments will be summarized. Furthermore, a critical analysis on failed trials of potentially meaningful targets such the nitric oxide and the orexinergic pathways will be conducted. Future perspective will be outlined. Expert opinion: The recent approval of Erenumab and Fremanezumab is a major milestone in the therapy of migraine since the approval of triptans. Several more studies are needed to fully understand the clinical potential, long-term safety and cost-effectiveness of these therapies. This paramount achievement should stimulate the development of further research in the migraine field.

Detection of Significant Association Between Variants in Cannabinoid Receptor 1 Gene (CNR1) and Personality in African-American Population

Background: Several studies have revealed significant associations between single nucleotide polymorphisms (SNPs) in the cannabinoid receptor 1 (CNR1) gene and a broad spectrum of psychiatric disorders such as major depressive disorder (MDD), attention deficit hyperactivity disorder (ADHD), and schizophrenia. Personality traits that are highly related to susceptibility to these conditions have been associated with the CNR1 variants in subjects of Caucasian origin. However, there are no reported studies regarding the effects of CNR1 polymorphisms on personality traits in the African-American (AA) population. Methods: We performed an imputation-based association analysis for 26 CNR1 variants with five dimensions of personality in 3,046 AAs. Results: SNPs rs806372 and rs2180619 showed a significant association with extraversion after Bonferroni correction for multiple testing (p < 0.0019). Further, several extraversion-associated SNPs were significantly associated with conscientiousness, agreeableness, and openness. SNP priority score analysis indicated that SNPs rs806368, rs806371, and rs2180619 play a role in the modulation of personality and psychiatric conditions. Conclusion:CNR1 is important in determining personality traits in the AA population.

Rare genetic variants in the endocannabinoid system genes CNR1 and DAGLA are associated with neurological phenotypes in humans

Rare genetic variants in the core endocannabinoid system genes CNR1, CNR2, DAGLA, MGLL and FAAH were identified in molecular testing data from 6,032 patients with a broad spectrum of neurological disorders. The variants were evaluated for association with phenotypes similar to those observed in the orthologous gene knockouts in mice. Heterozygous rare coding variants in CNR1, which encodes the type 1 cannabinoid receptor (CB1), were found to be significantly associated with pain sensitivity (especially migraine), sleep and memory disorders—alone or in combination with anxiety—compared to a set of controls without such CNR1 variants. Similarly, heterozygous rare variants in DAGLA, which encodes diacylglycerol lipase alpha, were found to be significantly associated with seizures and neurodevelopmental disorders, including autism and abnormalities of brain morphology, compared to controls. Rare variants in MGLL, FAAH and CNR2 were not associated with any neurological phenotypes in the patients tested. Diacylglycerol lipase alpha synthesizes the endocannabinoid 2-AG in the brain, which interacts with CB1 receptors. The phenotypes associated with rare CNR1 variants are reminiscent of those implicated in the theory of clinical endocannabinoid deficiency syndrome. The severe phenotypes associated with rare DAGLA variants underscore the critical role of rapid 2-AG synthesis and the endocannabinoid system in regulating neurological function and development. Mapping of the variants to the 3D structure of the type 1 cannabinoid receptor, or primary structure of diacylglycerol lipase alpha, reveals clustering of variants in certain structural regions and is consistent with impacts to function.

Anti-migraine effect of ∆9-tetrahydrocannabinol in the female rat

Current anti-migraine treatments have limited efficacy and many side effects. Although anecdotal evidence suggests that marijuana is useful for migraine, this hypothesis has not been tested in a controlled experiment. Thus, the present study tested whether administration of ∆⁹-tetrahydrocannabinol (THC) produces anti-migraine effects in the female rat. Microinjection of the TRPA1 agonist allyl isothiocyanate (AITC) onto the dura mater produced migraine-like pain for 3h as measured by depression of home cage wheel running. Concurrent systemic administration of 0.32 but not 0.1mg/kg of THC prevented AITC-induced depression of wheel running. However, 0.32mg/kg was ineffective when administered 90min after AITC. Administration of a higher dose of THC (1.0mg/kg) depressed wheel running whether rats were injected with AITC or not. Administration of a CB₁, but not a CB₂, receptor antagonist attenuated the anti-migraine effect of THC. These data suggest that: 1) THC reduces migraine-like pain when administered at the right dose (0.32mg/kg) and time (immediately after AITC); 2) THC's anti-migraine effect is mediated by CB₁ receptors; and 3) Wheel running is an effective method to assess migraine treatments because only treatments producing antinociception without disruptive side effects will restore normal activity. These findings support anecdotal evidence for the use of cannabinoids as a treatment for migraine in humans and implicate the CB₁ receptor as a therapeutic target for migraine.

Interactions between the Kynurenine and the Endocannabinoid System with Special Emphasis on Migraine

Both the kynurenine and the endocannabinoid systems are involved in several neurological disorders, such as migraine and there are increasing number of reports demonstrating that there are interactions of two systems. Although their cooperation has not yet been implicated in migraine, there are reports suggesting this possibility. Additionally, the individual role of the endocannabinoid and kynurenine system in migraine is reviewed here first, focusing on endocannabinoids, kynurenine metabolites, in particular kynurenic acid. Finally, the function of NMDA and cannabinoid receptors in the trigeminal system-which has a crucial role in the pathomechanisms of migraine-will also be discussed. The interaction of the endocannabinoid and kynurenine system has been demonstrated to be therapeutically relevant in a number of pathological conditions, such as cannabis addiction, psychosis, schizophrenia and epilepsy. Accordingly, the cross-talk of these two systems may imply potential mechanisms related to migraine, and may offer new approaches to manage the treatment of this neurological disorder.

Plasma levels of the endocannabinoid anandamide, related N-acylethanolamines and linoleic acid-derived oxylipins in patients with migraine

There is evidence that patients with migraine have deficient levels of the endogenous cannabinoid receptor ligand anandamide (AEA). It is not known, however, if this is a localised or generalised phenomenon. In the present study, levels of AEA, related N-acylethanolamines (NAEs) and linoleic acid-derived oxylipins have been measured in the blood of 26 healthy women and 38 women with migraine (26 with aura, 12 without aura) who were matched for age and body-mass index. Blood samples were taken on two occasions: the first sample near the start of the menstrual cycle (when present) and the second approximately fourteen days later. For a subset of migraine patients, two additional blood samples were taken, one during a migraine attack and one approximately 1 month later (to be at the same stage in the menstrual cycle, when present). NAEs and oxylipins were measured by liquid chromatography coupled to mass spectrometry. Twenty-nine lipids were quantified, of which 16 were found to have a high reproducibility of measurement. There were no significant differences in the levels of AEA, the related NAEs stearoylethanolamide and oleoylethanolamide or any of the nine linoleic acid-derived oxylipins measured either between migraine patients with vs. without aura, or between controls and migraine patients (after stratification to take into account whether or not the individuals had regular menstruation cycles) in either of the first two samples. Levels of linoleoylethanolamide were lower in the patients with vs. without aura on the second sample but not in the first sample, but the biological importance of this finding is unclear. Due to time-dependent increases in their concentrations ex vivo prior to centrifugation, AEA and oleoylethanolamide levels in the samples collected during migraine attacks were not analysed, but for the other fourteen lipids, there were no significant differences in plasma concentrations during migraine vs. one month later. It is concluded that migraine is not associated with a generalised (as opposed to localised) deficiency in these lipids.

The Use of Cannabis for Headache Disorders

Headache disorders are common, debilitating, and, in many cases, inadequately managed by existing treatments. Although clinical trials of cannabis for neuropathic pain have shown promising results, there has been limited research on its use, specifically for headache disorders. This review considers historical prescription practices, summarizes the existing reports on the use of cannabis for headache, and examines the preclinical literature exploring the role of exogenous and endogenous cannabinoids to alter headache pathophysiology. Currently, there is not enough evidence from well-designed clinical trials to support the use of cannabis for headache, but there are sufficient anecdotal and preliminary results, as well as plausible neurobiological mechanisms, to warrant properly designed clinical trials. Such trials are needed to determine short- and long-term efficacy for specific headache types, compatibility with existing treatments, optimal administration practices, as well as potential risks.

Variants in the CNR1 gene predispose to headache with nausea in the presence of life stress

One of the main effects of the endocannabinoid system in the brain is stress adaptation with presynaptic endocannabinoid receptor 1 (CB1 receptors) playing a major role. In the present study, we investigated whether the effect of the CB1 receptor coding CNR1 gene on migraine and its symptoms is conditional on life stress. In a cross-sectional European population (n = 2426), recruited from Manchester and Budapest, we used the ID-Migraine questionnaire for migraine screening, the Life Threatening Experiences questionnaire to measure recent negative life events (RLE), and covered the CNR1 gene with 11 SNPs. The main genetic effects and the CNR1 × RLE interaction with age and sex as covariates were tested. None of the SNPs showed main genetic effects on possible migraine or its symptoms, but 5 SNPs showed nominally significant interaction with RLE on headache with nausea using logistic regression models. The effect of rs806366 remained significant after correction for multiple testing and replicated in the subpopulations. This effect was independent from depression- and anxiety-related phenotypes. In addition, a Bayesian systems-based analysis demonstrated that in the development of headache with nausea all SNPs were more relevant with higher a posteriori probability in those who experienced recent life stress. In summary, the CNR1 gene in interaction with life stress increased the risk of headache with nausea suggesting a specific pathological mechanism to develop migraine, and indicating that a subgroup of migraine patients, who suffer from life stress triggered migraine with frequent nausea, may benefit from therapies that increase the endocannabinoid tone.

Clinical Endocannabinoid Deficiency Reconsidered: Current Research Supports the Theory in Migraine, Fibromyalgia, Irritable Bowel, and Other Treatment-Resistant Syndromes

Medicine continues to struggle in its approaches to numerous common subjective pain syndromes that lack objective signs and remain treatment resistant. Foremost among these are migraine, fibromyalgia, and irritable bowel syndrome, disorders that may overlap in their affected populations and whose sufferers have all endured the stigma of a psychosomatic label, as well as the failure of endless pharmacotherapeutic interventions with substandard benefit. The commonality in symptomatology in these conditions displaying hyperalgesia and central sensitization with possible common underlying pathophysiology suggests that a clinical endocannabinoid deficiency might characterize their origin. Its base hypothesis is that all humans have an underlying endocannabinoid tone that is a reflection of levels of the endocannabinoids, anandamide (arachidonylethanolamide), and 2-arachidonoylglycerol, their production, metabolism, and the relative abundance and state of cannabinoid receptors. Its theory is that in certain conditions, whether congenital or acquired, endocannabinoid tone becomes deficient and productive of pathophysiological syndromes. When first proposed in 2001 and subsequently, this theory was based on genetic overlap and comorbidity, patterns of symptomatology that could be mediated by the endocannabinoid system (ECS), and the fact that exogenous cannabinoid treatment frequently provided symptomatic benefit. However, objective proof and formal clinical trial data were lacking. Currently, however, statistically significant differences in cerebrospinal fluid anandamide levels have been documented in migraineurs, and advanced imaging studies have demonstrated ECS hypofunction in post-traumatic stress disorder. Additional studies have provided a firmer foundation for the theory, while clinical data have also produced evidence for decreased pain, improved sleep, and other benefits to cannabinoid treatment and adjunctive lifestyle approaches affecting the ECS.

High Times for Painful Blues: The Endocannabinoid System in Pain-Depression Comorbidity

Depression and pain are two of the most debilitating disorders worldwide and have an estimated cooccurrence of up to 80%. Comorbidity of these disorders is more difficult to treat, associated with significant disability and impaired health-related quality of life than either condition alone, resulting in enormous social and economic cost. Several neural substrates have been identified as potential mediators in the association between depression and pain, including neuroanatomical reorganization, monoamine and neurotrophin depletion, dysregulation of the hypothalamo-pituitary-adrenal axis, and neuroinflammation. However, the past decade has seen mounting evidence supporting a role for the endogenous cannabinoid (endocannabinoid) system in affective and nociceptive processing, and thus, alterations in this system may play a key role in reciprocal interactions between depression and pain. This review will provide an overview of the preclinical evidence supporting an interaction between depression and pain and the evidence supporting a role for the endocannabinoid system in this interaction.

Comprehensive Review of Medicinal Marijuana, Cannabinoids, and Therapeutic Implications in Medicine and Headache: What a Long Strange Trip It's Been …

BACKGROUND

The use of cannabis, or marijuana, for medicinal purposes is deeply rooted though history, dating back to ancient times. It once held a prominent position in the history of medicine, recommended by many eminent physicians for numerous diseases, particularly headache and migraine. Through the decades, this plant has taken a fascinating journey from a legal and frequently prescribed status to illegal, driven by political and social factors rather than by science. However, with an abundance of growing support for its multitude of medicinal uses, the misguided stigma of cannabis is fading, and there has been a dramatic push for legalizing medicinal cannabis and research. Almost half of the United States has now legalized medicinal cannabis, several states have legalized recreational use, and others have legalized cannabidiol-only use, which is one of many therapeutic cannabinoids extracted from cannabis. Physicians need to be educated on the history, pharmacology, clinical indications, and proper clinical use of cannabis, as patients will inevitably inquire about it for many diseases, including chronic pain and headache disorders for which there is some intriguing supportive evidence.

OBJECTIVE

To review the history of medicinal cannabis use, discuss the pharmacology and physiology of the endocannabinoid system and cannabis-derived cannabinoids, perform a comprehensive literature review of the clinical uses of medicinal cannabis and cannabinoids with a focus on migraine and other headache disorders, and outline general clinical practice guidelines.

CONCLUSION

The literature suggests that the medicinal use of cannabis may have a therapeutic role for a multitude of diseases, particularly chronic pain disorders including headache. Supporting literature suggests a role for medicinal cannabis and cannabinoids in several types of headache disorders including migraine and cluster headache, although it is primarily limited to case based, anecdotal, or laboratory-based scientific research. Cannabis contains an extensive number of pharmacological and biochemical compounds, of which only a minority are understood, so many potential therapeutic uses likely remain undiscovered. Cannabinoids appear to modulate and interact at many pathways inherent to migraine, triptan mechanisms ofaction, and opiate pathways, suggesting potential synergistic or similar benefits. Modulation of the endocannabinoid system through agonism or antagonism of its receptors, targeting its metabolic pathways, or combining cannabinoids with other analgesics for synergistic effects, may provide the foundation for many new classes of medications. Despite the limited evidence and research suggesting a role for cannabis and cannabinoids in some headache disorders, randomized clinical trials are lacking and necessary for confirmation and further evaluation.

Update on the genetics of the fibromyalgia syndrome

Fibromyalgia syndrome (FMS), a condition characterized by chronic widespread pain and tenderness, is a complex condition considered to represent a paradigm of centralized pain. FMS has demonstrated a clear familial aggregation, and hence it is considered to have a genetic background. Multiple candidate-gene studies have been conducted in this field, focusing on target genes that play a role in the transmission and processing of pain. While many of these have focused in the past on markers related to neurotransmitter systems such as catecholamines (catechol-O-methyltransferase (COMT)) and serotonin, novel target genes have recently emerged. In addition, genome-wide sequencing scanning (genome-wide association study (GWAS)) is increasingly being harnessed for the study of chronic pain, including FMS. Micro RNAs are another novel field of research related to posttranscriptional inhibition of gene expression, which are currently regarding the pathogenesis of FMS.

Irritable bowel syndrome and migraine: bystanders or partners?

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

Genetic variants in the catechol-o-methyltransferase gene are associated with impulsivity and executive function: relevance for major depression

The catechol-o-methyltransferase (COMT) gene has been extensively investigated in depression with somewhat contradictory results but the role of impulsivity, as a possible intermediate phenotype in this disorder, has not been considered yet. In our study, four tagging SNPs in the COMT gene (rs933271, rs740603, rs4680, rs4646316) were genotyped in two independent population cohorts: Manchester (n = 1267) and Budapest (n = 942). First, we investigated the association between COMT genotypes, impulsivity, neuroticism and depression using haplotype trend regression, and constructed a model using structural equation modeling to investigate the interaction between these factors. Secondly, we tested the effect of executive function on this model in a smaller interviewed sample (n = 207). Our results demonstrated that COMT haplotypes were significantly associated with impulsivity in the combined cohort, showing the same direction of effects in both populations. The COMT effect on depressive symptoms (in subjects without history of depression) and on executive function (interviewed sample) showed the opposite pattern to impulsivity. Structural equation models demonstrated that COMT and impulsivity acted, both together (through neuroticism) and independently, to increase the risk of depression. In addition, better executive function also operated as a risk factor for depression, possibly though reduced ability to flexibly disengage negative emotions. In conclusion, variations in the COMT gene exert complex effects on susceptibility to depression involving various intermediate phenotypes, such as impulsivity and executive function. These findings emphasise that modeling of disease pathways at phenotypic level are valuable for identifying genetic risk factors.

Large candidate gene association study reveals genetic risk factors and therapeutic targets for fibromyalgia

OBJECTIVE

Fibromyalgia (FM) represents a complex disorder that is characterized by widespread pain and tenderness and is frequently accompanied by additional somatic and cognitive/affective symptoms. Genetic risk factors are known to contribute to the etiology of the syndrome. The aim of this study was to examine >350 genes for association with FM, using a large-scale candidate gene approach.

METHODS

The study group comprised 496 patients with FM (cases) and 348 individuals with no chronic pain (controls). Genotyping was performed using a dedicated gene array chip, the Pain Research Panel, which assays variants characterizing >350 genes known to be involved in the biologic pathways relevant to nociception, inflammation, and mood. Association testing was performed using logistic regression.

RESULTS

Significant differences in allele frequencies between cases and controls were observed for 3 genes: GABRB3 (rs4906902; P = 3.65 × 10(-6)), TAAR1 (rs8192619; P = 1.11 × 10(-5)), and GBP1 (rs7911; P = 1.06 × 10(-4)). These 3 genes and 7 other genes with suggestive evidence for association were examined in a second, independent cohort of patients with FM and control subjects who were genotyped using the Perlegen 600K platform. Evidence of association in the replication cohort was observed for TAAR1, RGS4, CNR1, and GRIA4.

CONCLUSION

Variation in these 4 replicated genes may serve as a basis for development of new diagnostic approaches, and the products of these genes may contribute to the pathophysiology of FM and represent potential targets for therapeutic action.

Bitter taster status predicts susceptibility to vection-induced motion sickness and nausea

BACKGROUND

Sensitivity to bitter taste and susceptibility to nausea are both protective mechanisms that guard against toxin ingestion, and both these traits vary within and between populations. Thus, we postulated that they may have co-evolved, such that they are associated.

METHODS

Bitter taster status was determined in 40 subjects (13 men, 27 women) by measuring the differential perceived taste intensity between salt and n-propylthiouracil using a labeled magnitude scale; susceptibility to vection-induced motion sickness and nausea was assessed using an optokinetic drum, a validated multi-symptom scoring scale, and electrogastrography.

KEY RESULTS

Taster status distribution was 25% non-tasters (NT), 40% tasters (T), and 35% supertasters (ST). Gender had no impact on this distribution, but females had a higher mean maximum symptom score than males (12.4 ± 1.4 vs 7.3 ± 2.0). Non-tasters displayed a faster and larger increase in mean symptom scores, had a higher percentage of subjects with high maximum symptom scores, and had a higher mean maximum score than T or ST, (14.8 ± 2.6 vs 7.1 ± 1.8, vs 9.8 ± 2.0). Taster status did not affect the gastric myoelectric frequency response to vection.

CONCLUSIONS & INFERENCES

Non-tasters are more susceptible to vection-induced motion sickness and nausea than T or ST, suggesting these two traits may have co-evolved in a reciprocal manner: in environments where the NT trait conferred an evolutionary advantage by enabling intake of fruits and vegetables containing bitter, yet beneficial, phytonutrients, increased nausea susceptibility may have arisen to maintain protection against ingested toxins.

Contributions of endocannabinoid signaling to psychiatric disorders in humans: genetic and biochemical evidence

The endocannabinoid signaling system is a widespread, neuromodulatory system in brain and is also widely utilized in the periphery to modulate metabolic functions and the immune system. Preclinical data demonstrate that endocannabinoid signaling is an important stress buffer and modulates emotional and cognitive functions. These data suggest the hypothesis that endocannabinoid signaling could be dysfunctional in a number of mental disorders. Genetic polymorphisms in the human genes for two important proteins of the endocannabinoid signaling system, the CB1 cannabinoid receptor (CB1R) and fatty acid amide hydrolase (FAAH), have been explored in the context of normal and pathological conditions. In the case of the gene for FAAH, the mechanistic relationships among the common genetic polymorphism, the expression of the FAAH protein, and its likely impact on endocannabinoid signaling are understood. However, multiple polymorphisms in the gene for the CB1R occur and are associated with human phenotypic differences without an understanding of the functional relationships among the gene, mRNA, protein, and protein function. The endocannabinoid ligands are found in the circulation, and several studies have identified changes in their concentrations under various conditions. These data are reviewed for the purpose of generating hypotheses and to encourage further studies in this very interesting and important area.

Interictal type 1 cannabinoid receptor binding is increased in female migraine patients

OBJECTIVE

To compare binding of the type 1 cannabinoid receptor (CB1R) between migraine patients and healthy volunteers.

BACKGROUND

It has been suggested that endocannabinoid deficiency may play a role in the pathophysiology of migraine. Nonetheless, biochemical studies substantiating this idea remain scarce and are faced with methodological shortcomings partly because of the difficulty to perform measurements of endocannabinoids within the central nervous system itself.

METHODS

An observational cross-sectional study was conducted in 20 female migraine patients and 18 healthy women matched for age and body mass index. Positron emission tomography acquisition was performed 90 minutes after intravenous injection of the radioligand [(18)F]MK-9470 to assess binding of [(18)F]MK-9470 to CB1R.

RESULTS

Binding of CB1 R was globally increased in migraine patients vs healthy controls (average gray matter difference +16%; P = .009, 2-sample 2-sided Student's t-test). There were no correlations between CB1R binding and any predefined migraine characteristics. Increases in CB1R binding were most pronounced in the anterior cingulate, mesial temporal, prefrontal, and superior frontal cortices.

CONCLUSION

The increased interictal CB1R binding, especially in brain regions that exert top-down influences to modulate pain, supports the idea that endocannibinoid deficiency is present in female patients suffering from episodic migraine.

Nutraceuticals and headache: the biological basis

Nutrition must affect the structure and functioning of the brain. Since the brain has very high metabolic activity, what we consume throughout the day is likely to dramatically influence both its structure and moment to moment function. It follows that nutritional approaches to all neurological disorders are being researched and entering medical practice, while nutraceutical use is a mainstay of public habits. This review discusses the biological basis for non-conventional or non-mainstream approaches to the treatment of migraine. This requires at least limited discussion of current migraine pathophysiologic theory. How nutrients and other chemicals and approaches are mechanistically involved within migraine pathways is the focus of this article. The nutraceuticals reviewed in detail are: magnesium, riboflavin, coenzyme Q10, petasites, and feverfew with additional comments on marijuana and oxygen/hyperbaric oxygen. This article reviews the science when known related to the potential genetic susceptibility and sensitivity to these treatments. As we know, the basic science in this field is very preliminary, so whether to combine approaches and presumably mechanisms or use them alone or with or without conventional therapies is far from clear. Nonetheless, as more patients and providers participate in patient-centered approaches to care, knowledge of the science underpinning nutritional, nutraceutical, and complementary approaches to treatment for migraine will certainly benefit this interaction.

Motion sickness, stress and the endocannabinoid system

Background

A substantial number of individuals are at risk for the development of motion sickness induced nausea and vomiting (N&V) during road, air or sea travel. Motion sickness can be extremely stressful but the neurobiologic mechanisms leading to motion sickness are not clear. The endocannabinoid system (ECS) represents an important neuromodulator of stress and N&V. Inhibitory effects of the ECS on N&V are mediated by endocannabinoid-receptor activation.

Methodology/Principal Findings

We studied the activity of the ECS in human volunteers (n = 21) during parabolic flight maneuvers (PFs). During PFs, microgravity conditions (<10⁻² g) are generated for approximately 22 s which results in a profound kinetic stimulus. Blood endocannabinoids (anandamide and 2-arachidonoylglycerol, 2-AG) were measured from blood samples taken in-flight before start of the parabolic maneuvers, after 10, 20, and 30 parabolas, in-flight after termination of PFs and 24 h later. Volunteers who developed acute motion sickness (n = 7) showed significantly higher stress scores but lower endocannabinoid levels during PFs. After 20 parabolas, blood anandamide levels had dropped significantly in volunteers with motion sickness (from 0.39±0.40 to 0.22±0.25 ng/ml) but increased in participants without the condition (from 0.43±0.23 to 0.60±0.38 ng/ml) resulting in significantly higher anandamide levels in participants without motion sickness (p = 0.02). 2-AG levels in individuals with motion sickness were low and almost unchanged throughout the experiment but showed a robust increase in participants without motion sickness. Cannabinoid-receptor 1 (CB1) but not cannabinoid-receptor 2 (CB2) mRNA expression in leucocytes 4 h after the experiment was significantly lower in volunteers with motion sickness than in participants without N&V.

Conclusions/Significance

These findings demonstrate that stress and motion sickness in humans are associated with impaired endocannabinoid activity. Enhancing ECS signaling may represent an alternative therapeutic strategy for motion sickness in individuals who do not respond to currently available treatments.

Headache-type adverse effects of NO donors: vasodilation and beyond

Although nitrate therapy, used in the treatment of cardiovascular disorders, is frequently associated with side-effects, mainly headaches, the summaries of product characteristics of nitrate-containing medicines do not report detailed description of headaches and even do not highlight the possibility of nitrate-induced migraine. Two different types of nitrate-induced headaches have been described: (i) immediate headaches that develop within the first hour of the application, are mild or medium severity without characteristic symptoms for migraine, and ease spontaneously; and (ii) delayed, moderate or severe migraine-type headaches (occurring mainly in subjects with personal or family history of migraine), that develop 3-6 h after the intake of nitrates, with debilitating, long-lasting symptoms including nausea, vomiting, photo- and/or phono-phobia. These two types of headaches are remarkably different, not only in their timing and symptoms, but also in the persons who are at risk. Recent studies provide evidence that the two headache types are caused by different mechanisms: immediate headaches are connected to vasodilation caused by nitric oxide (NO) release, while migraines are triggered by other actions such as the release of calcitonin gene-related peptide or glutamate, or changes in ion channel function mediated by cyclic guanosine monophosphate or S-nitrosylation. Migraines usually need anti-attack medication, such as triptans, but these drugs are contraindicated in most medical conditions that are treated using nitrates. In conclusion, these data recommend the correction of summaries of nitrate product characteristics, and also suggest a need to develop new types of anti-migraine drugs, effective in migraine attacks, that could be used in patients with risk for angina pectoris.