The selective PAC1 receptor agonist maxadilan inhibits neurogenic vasodilation and edema formation in the mouse skin

Toxicological evaluation of a nonlethal riot control combinational formulation upon dermal application using animal models

Numerous adverse effects on human health have been reported in epidemiological studies of oleoresin capsicum (OC) and other riot control agents (RCAs). Importantly, the daunting risk of such RCAs can be neutralized by optimizing the desired concentration of such agents for mob dispersal. Hence, a nonlethal riot control combinational formulation (NCF) was prepared for dispersing rioters without imparting fatal outcomes. However, for desired utilization of NCF, it is essential to recognize its extent of potential toxicity. Therefore, the current investigation evaluated the dermal toxicity of NCF using experimental animals in compliance with the OECD guidelines. Additionally, few essential metal ions were analyzed and found non -significantly different in the test rats as compared to control rats. Moreover, abnormal dermal morphology and lesions ultrastructural tissue defects were not noticed as evinced by different studies like ultrasonography, histology, and scanning electron microscopy (SEM) respectively. Further, Doppler ultrasonography exhibited non-significantly different blood flow velocity in both groups, whereas miles test demonstrated a significantly increased Evans blue concentration in test rats compared to the control rats, which might be due to an initial increase in blood flow via an instant action of the NCF at the cutaneous sensory nerve endings. However, our results demonstrated NCF can produce initial skin irritating and sensitizing effects in guinea pigs and rabbits without the antecedence of acute toxicity (≤2000 mg/kg) in Wistar rats.

Mechanistic evaluation of a novel cyclohexenone derivative's functionality against nociception and inflammation: An in-vitro, in-vivo and in-silico approach

The synthesis of a novel cyclohexanone derivative (CHD; Ethyl 6-(4-metohxyphenyl)-2-oxo-4-phenylcyclohexe-3-enecarboxylate) was described and the subsequent aim was to perform an in vitro, in vivo and in silico pharmacological evaluation as a putative anti-nociceptive and anti-inflammatory agent in mice. Initial in vitro studies revealed that CHD inhibited both cyclooxygenase-2 (COX-2) and 5-lipoxygenase (5-LOX) enzymes and it also reduced mRNA expression of COX-2 and the pro-inflammatory cytokines TNF-α and IL-1β. It was then shown that CHD dose dependently inhibited chemically induced tonic nociception in the abdominal constriction assay and also phasic thermal nociception (i.e. anti-nociception) in the hot plate and tail immersion tests in comparison with aspirin and tramadol respectively. The thermal test outcomes indicated a possible moderate centrally mediated anti-nociception which, in the case of the hot plate test, was pentylenetetrazole (PTZ) and naloxone reversible, implicating GABAergic and opioidergic mechanisms. CHD was also effective against both the neurogenic and inflammatory mediator phases induced in the formalin test and it also disclosed anti-inflammatory activity against the phlogistic agents, carrageenan, serotonin, histamine and xylene compared with standard drugs in edema volume tests. In silico studies indicated that CHD possessed preferential affinity for GABAA, opioid and COX-2 target sites and this was supported by molecular dynamic simulations where computation of free energy of binding also favored the formation of stable complexes with these sites. These findings suggest that CHD has prospective anti-nociceptive and anti-inflammatory properties, probably mediated through GABAergic and opioidergic interactions supplemented by COX-2 and 5-LOX enzyme inhibition in addition to reducing pro-inflammatory cytokine expression. CHD may therefore possess potentially beneficial therapeutic effectiveness in the management of inflammation and pain.

Infusion of Pituitary Adenylate Cyclase-Activating Polypeptide-38 in Patients with Rosacea Induces Flushing and Facial Edema that Can Be Attenuated by Sumatriptan

BACKGROUND

The pathogenesis of rosacea is incompletely understood. Signaling neuropeptides, including PACAP, a regulator of vasodilation and edema, are upregulated in rosacea skin. Here, we evaluated PACAP38-induced rosacea features and examined whether a 5-HT_1B/1D receptor agonist could reduce these features.

METHODS

A total of 35 patients with erythematotelangiectatic rosacea received an intravenous infusion of 10 pmol/kg/minute of PACAP38 followed by an intravenous infusion of 4 mg sumatriptan or placebo (saline) on two study days in a double-blind, randomized, placebo-controlled, and cross-over trial.

RESULTS

PACAP38 increased facial skin blood flow by 90%, dilated the superficial temporal artery by 56%, and induced prolonged flushing and facial edema. Compared with placebo, sumatriptan reduced PACAP38-induced facial skin blood flow for 50 minutes (P = 0.023), constricted the superficial temporal artery for 80 minutes (P = 0.010), and reduced duration of flushing (P = 0.001) and facial edema (P < 0.001).

CONCLUSIONS

We established a clinical experimental model of rosacea features and showed that sumatriptan was able to attenuate PACAP38-induced rosacea flushing and edema. Findings support a key role of PACAP38 in rosacea flushing pathogenesis. It remains unknown whether PACAP38 inhibition can improve rosacea.

TRIAL REGISTER

The trial was registered at ClinicalTrials.govNCT03878784 in March 2019.

Pituitary Adenylate Cyclase-Activating Polypeptide: A Promising Neuroprotective Peptide in Stroke

The search for viable, effective treatments for acute stroke continues to be a global priority due to the high mortality and morbidity. Current therapeutic treatments have limited effects, making the search for new treatments imperative. Pituitary adenylate cyclase-activating polypeptide (PACAP) is a well-established cytoprotective neuropeptide that participates in diverse neural physiological and pathological activities, such as neuronal proliferation, differentiation, and migration, as well as neuroprotection. It is considered a promising treatment in numerous neurological diseases. Thus, PACAP bears potential as a new therapeutic strategy for stroke treatment. Herein, we provide an overview pertaining to the current knowledge of PACAP, its receptors, and its potential neuroprotective role in the setting of stroke, as well as various mechanisms of neuroprotection involving ionic homeostasis, excitotoxicity, cell edema, oxidative stress, inflammation, and cell death, as well as the route of PACAP administration.

Pituitary Adenylate Cyclase-Activating Polypeptide Attenuates Brain Edema by Protecting Blood-Brain Barrier and Glymphatic System After Subarachnoid Hemorrhage in Rats

Brain edema is a vital contributor to early brain injury after subarachnoid hemorrhage (SAH), which is responsible for prolonged hospitalization and poor outcomes. Pharmacological therapeutic targets on edema formation have been the focus of research for decades. Pituitary adenylate cyclase-activating polypeptide (PACAP) has been shown to participate in neural development and brain injury. Here, we used PACAP knockout CRISPR to demonstrate that endogenous PACAP plays an endogenous neuroprotective role against brain edema formation after SAH in rats. The exogenous PACAP treatment provided both short- and long-term neurological benefits by preserving the function of the blood-brain barrier and glymphatic system after SAH. Pretreatment of inhibitors of PACAP receptors showed that the PACAP-involved anti-edema effect and neuroprotection after SAH was facilitated by the selective PACAP receptor (PAC1). Further administration of adenylyl cyclase (AC) inhibitor and sulfonylurea receptor 1 (SUR1) CRISPR activator suggested that the AC-cyclic adenosine monophosphate (cAMP)-protein kinase A (PKA) axis participated in PACAP signaling after SAH, which inhibited the expression of edema-related proteins, SUR1 and aquaporin-4 (AQP4), through SUR1 phosphorylation. Thus, PACAP may serve as a potential clinical treatment to alleviate brain edema in patients with SAH.

Evaluation of Methanol-Dichloromethane Extract of Stemonocoleus micranthus Harms (Fabaceae) Stem Bark for Anti-Inflammatory and Immunomodulatory Activities

BACKGROUND

The stem bark decoction of Stemonocoleus micranthus Harms (Fabaceae) is most widely used traditionally as a remedy for various diseases such as malaria and boil. In this study, the anti-inflammatory and immunomodulatory activities of the methanol-dichloromethane extract (MDE) from the stem bark of the plant in rodents were evaluated.

METHODS

The carrageenan-induced rat paw oedema, cotton pellet-induced granuloma in rat, and xylene-induced ear oedema in mice were used to study the anti-inflammatory activity of methanol-dichloromethane extract of Stemonocoleus micranthus (MDESm) (100, 200, and 400 mg/kg). The effects of MDESm (100, 200, and 400 mg/kg) on cyclophosphamide-induced immunosuppression, neutrophil adhesion, carbon clearance, and haematological and biochemical parameters were carried out to study its immunomodulatory activity in mice.

RESULT

MDESm (100 mg/kg, p.o.) significantly (p < 0.05) inhibited carrageenan-induced oedema by 57.1% at 5th h posttreatment compared with control. At 100 mg/kg, p.o., MDESm significantly (p < 0.05) reduced cotton pellet-induced granuloma by 39.28% and nonsignificantly reduced xylene-induced ear oedema by 34.1%. Treatment with MDESm (100 and 400 mg/kg) nonsignificantly abolished the neutropenia caused by cyclophosphamide with a percentage neutrophil reduction of 0 and -14.86%, respectively, while MDESm (200 mg/kg) and levamisole (50 mg/kg) had a nonsignificant reduction in neutrophil count (10.16 and 31.40%), respectively, all compared to the distilled water-treated group with a neutrophil count of -9.82%. MDESm at doses of 100 and 200 mg/kg increased phagocytic index by 0.0447 ± 0.00762 and 0.0466 ± 0.00703, respectively, although not significantly when compared to the control group with a value of 0.0226 ± 0.02117. There was a decrease in WBC and lymphocyte counts in MDESm- (200 mg/kg) treated group, suggesting immunosuppressive potential at this dose. MDESm caused a dose-dependent decrease in ALT and core liver enzymes, suggesting a hepatoprotective effect. The acute toxicity test revealed that MDESm is safe in mice with an oral lethal dose (LD50) of >5 g/kg.

CONCLUSION

The methanol-dichloromethane extract of Stemonocoleus micranthus Harms possesses mild anti-inflammatory and immunomodulatory activities which may be more pronounced upon fractionation and purification. Therefore, more investigations are needed to explore these activities further.

Neurotransmitters, neuropeptides and their receptors interact with immune response in healthy and psoriatic skin

Psoriasis is a chronic inflammatory disease with a multifactorial origin that affects the skin. It is characterized by keratinocyte hyperproliferation, which results in erythemato-squamous plaques. Just as the immune system plays a fundamental role in psoriasis physiopathology, the nervous system maintains the inflammatory process through the neuropeptides and neurotransmitters synthesis, as histamine, serotonin, calcitonin gene-related peptide, nerve growth factor, vasoactive intestinal peptide, substance P, adenosine, glucagon-like peptide, somatostatin and pituitary adenylate cyclase polypeptide. In patients with psoriasis, the systemic or in situ expression of these chemical mediators and their receptors are altered, which affects the clinical activity of patients due to its link to the immune system, provoking neurogenic inflammation. It is important to establish the role of the nervous system since it could represent a therapeutic alternative for psoriasis patients. The aim of this review is to offer a detailed review of the current literature about the neuropeptides and neurotransmitters involved in the physiopathology of psoriasis.

Protective Effects of PACAP in Peripheral Organs

Pituitary adenylate cyclase activating polypeptide (PACAP) is a neuropeptide widely distributed in the nervous system, where it exerts strong neuroprotective effects. PACAP is also expressed in peripheral organs but its peripheral protective effects have not been summarized so far. Therefore, the aim of the present paper is to review the existing literature regarding the cytoprotective effects of PACAP in non-neuronal cell types, peripheral tissues, and organs. Among others, PACAP has widespread expression in the digestive system, where it shows protective effects in various intestinal pathologies, such as duodenal ulcer, small bowel ischemia, and intestinal inflammation. PACAP is present in both the exocrine and endocrine pancreas as well as liver where it reduces inflammation and steatosis by interfering with hepatic pathology related to obesity. It is found in several exocrine glands and also in urinary organs, where, with its protective effects being mainly published regarding renal pathologies, PACAP is protective in numerous conditions. PACAP displays anti-inflammatory effects in upper and lower airways of the respiratory system. In the skin, it is involved in the development of inflammatory pathology such as psoriasis and also has anti-allergic effects in a model of contact dermatitis. In the non-neuronal part of the visual system, PACAP showed protective effects in pathological conditions of the cornea and retinal pigment epithelial cells. The positive role of PACAP has been demonstrated on the formation and healing processes of cartilage and bone where it also prevents osteoarthritis and rheumatoid arthritis development. The protective role of PACAP was also demonstrated in the cardiovascular system in different pathological processes including hyperglycaemia-induced endothelial dysfunction and age-related vascular changes. In the heart, PACAP protects against ischemia, oxidative stress, and cardiomyopathies. PACAP is also involved in the protection against the development of pre-senile systemic amyloidosis, which is presented in various peripheral organs in PACAP-deficient mice. The studies summarized here provide strong evidence for the cytoprotective effects of the peptide. The survival-promoting effects of PACAP depend on a number of factors which are also shortly discussed in the present review.

Antinociceptive and anti-inflammatory properties of Tetracera alnifolia Willd. (Dilleniaceae) hydroethanolic leaf extract

Background Tetracera alnifolia Willd. (Dilleniaceae) is used in traditional African Medicine for the treatment of headache, abdominal pain, and rheumatism. Hence, this study sought to investigate the antinociceptive and anti-inflammatory effects of the hydroethanolic leaf extract of T. alnifolia (HeTA) in rodents. Methods Antinociceptive activity was evaluated using the acetic acid-induced writhing, formalin-/capsaicin-induced paw licking and hot plate tests in mice. The contribution of opioidergic, l-arginine-nitric oxide, and ATP-sensitive potassium channel pathways in HeTA-induced antinociception was also evaluated. The anti-inflammatory effect was assessed using the carrageenan-induced paw edema, xylene ear edema, cotton pellet granuloma, and complete Freund's adjuvant (CFA)-induced arthritis in rats. Results HeTA (100, 200, and 400 mg/kg, p.o.) produced significant (p<0.05) decrease in mean number of acetic acid-induced writhing, time spent licking paw in formalin, and capsaicin tests as well as time course increase in nociceptive reaction latency in hot plate test. HeTA-induced antinociception was prevented by pretreatment of mice with naloxone (non-selective opioid receptor antagonist), l-arginine (nitric oxide precursor), or glibenclamide (ATP-sensitive potassium channel blocker). HeTA (100 mg/kg, p.o.) produced a significant anti-inflammatory effect against carrageenan-induced rat paw edema (1-5 h), xylene-induced ear edema, cotton pellet-induced granuloma formation, and CFA-induced arthritis in rats. The effects of HeTA in various models were similar to the effect of the standard reference drugs. Conclusions Findings from this study showed that HeTA possesses antinociceptive effect possibly mediated through peripheral opioid receptors with activation of l-arginine-nitric oxide and ATP-sensitive potassium channel pathway as well as anti-inflammatory activity.

Presence and Effects of Pituitary Adenylate Cyclase Activating Polypeptide Under Physiological and Pathological Conditions in the Stomach

Pituitary adenylate cyclase activating polypeptide (PACAP) is a multifunctional neuropeptide with widespread occurrence throughout the body including the gastrointestinal system. In the small and large intestine, effects of PACAP on cell proliferation, secretion, motility, gut immunology and blood flow, as well as its importance in bowel inflammatory reactions and cancer development have been shown and reviewed earlier. However, no current review is available on the actions of PACAP in the stomach in spite of numerous data published on the gastric presence and actions of the peptide. Therefore, the aim of the present review is to summarize currently available data on the distribution and effects of PACAP in the stomach. We review data on the localization of PACAP and its receptors in the stomach wall of various mammalian and non-mammalian species, we then give an overview on PACAP's effects on secretion of gastric acid and various hormones. Effects on cell proliferation, differentiation, blood flow and gastric motility are also reviewed. Finally, we outline PACAP's involvement and changes in various human pathological conditions.

Anti-inflammatory, Antinociceptive, and Antioxidant Activities of Methanol and Aqueous Extracts of Anacyclus pyrethrum Roots

Anacyclus pyrethrum (L.) is a plant widely used in Moroccan traditional medicine to treat inflammatory and painful diseases. The objective of the present study was to evaluate the antinociceptive, anti-inflammatory and antioxidant activities of aqueous and methanol extracts of Anacyclus pyrethrum roots (AEAPR and MEAPR). The anti-inflammatory effect of AEAPR and MEAPR was determined in xylene–induced ear edema and Complete Freund’s Adjuvant (CFA)-induced paw edema. The antinociceptive activity of AEAPR and MEAPR (125, 250, and 500 mg/kg) administered by gavage was examined in mice by using acetic acid-induced writhing, hot plate, and formalin tests, and the mechanical allodynia were assessed in CFA-induced paw edema. In addition, the in vitro antioxidant activities of the extracts were determined by using 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging method, ferric reducing power and β-carotene-linoleic acid assay systems. AEAPR and MEAPR produced significant reductions in CFA-induced paw edema and xylene-induced ear edema. A single oral administration of these extracts at 250 and 500 mg/kg significantly reduced mechanical hypersensitivity induced by CFA, which had begun 1 h 30 after the treatment, and was maintained till 7 h. Chronic treatment with both extracts significantly reduced mechanical hypersensitivity in persistent pain conditions induced by CFA. Acute pretreatment with AEAPR or MEAPR at high dose caused a significant decrease in the number of abdominal writhes induced by acetic acid injection (52.2 and 56.7%, respectively), a marked increase of the paw withdrawal latency in the hot plate test, and also a significant inhibition of both phases of the formalin test. This antinociceptive effect was partially reversed by naloxone pretreatment in the hot plate and formalin tests. Additionally, a significant scavenging activity in DPPH, reducing power and protection capacity of β-carotene was observed in testing antioxidant assays. The present study suggests that AEAPR and MEAPR possess potent anti-inflammatory, antinociceptive and antioxidant effects which could be related to the presence of alkaloids and phenols in the plant. In addition, the antinociceptive effect of APR extracts seems to partly involve the opioid system. Taken together, these results suggest that Anacylcus pyrethrum may indeed be useful in the treatment of pain and inflammatory disorders in humans.

Effects of friction massage of the popliteal fossa on blood flow velocity of the popliteal vein

[Purpose] Friction massage (friction) of the popliteal fossa is provided for the purpose of relieving pain related to circulatory disorders by improving venous flow in the lower legs. The purpose of this study is to verify the effects of enhancing the venous flow based on measuring the blood flow velocity of the popliteal vein before and after providing friction to the patients. [Subjects and Methods] Fifteen healthy male university students participated in the study. The Doppler ultrasonography (DU) was used to measure the blood flow velocity of the popliteal vein, in order to verify the effects of enhancing the venous flow by comparing the measured values before and after a friction massage. [Results] The result of comparing the blood flow velocity before and after providing friction showed that there was a significant increase after friction. [Conclusion] This study proved that friction to the popliteal fossa is effectively enhances venous flow by increasing the blood flow velocity in the popliteal vein.

The Protective Role of PAC1-Receptor Agonist Maxadilan in BCCAO-Induced Retinal Degeneration

A number of studies have proven that pituitary adenylate cyclase activating polypeptide (PACAP) is protective in neurodegenerative diseases. Permanent bilateral common carotid artery occlusion (BCCAO) causes severe degeneration in the rat retina. In our previous studies, protective effects were observed with PACAP1-38, PACAP1-27, and VIP but not with their related peptides, glucagon, or secretin in BCCAO. All three PACAP receptors (PAC1, VPAC1, VPAC2) appear in the retina. Molecular and immunohistochemical analysis demonstrated that the retinoprotective effects are most probably mainly mediated by the PAC1 receptor. The aim of the present study was to investigate the retinoprotective effects of a selective PAC1-receptor agonist maxadilan in BCCAO-induced retinopathy. Wistar rats were used in the experiment. After performing BCCAO, the right eye was treated with intravitreal maxadilan (0.1 or 1 μM), while the left eye was injected with vehicle. Sham-operated rats received the same treatment. Two weeks after the operation, retinas were processed for standard morphometric and molecular analysis. Intravitreal injection of 0.1 or 1 μM maxadilan caused significant protection in the thickness of most retinal layers and the number of cells in the GCL compared to the BCCAO-operated eyes. In addition, 1 μM maxadilan application was more effective than 0.1 μM maxadilan treatment in the ONL, INL, IPL, and the entire retina (OLM-ILM). Maxadilan treatment significantly decreased cytokine expression (CINC-1, IL-1α, and L-selectin) in ischemia. In summary, our histological and molecular analysis showed that maxadilan, a selective PAC1 receptor agonist, has a protective role in BCCAO-induced retinal degeneration, further supporting the role of PAC1 receptor conveying the retinoprotective effects of PACAP.

Anti-inflammatory activity of aqueous extract and bioactive compounds identified from the fruits of Hancornia speciosa Gomes (Apocynaceae)

Background

Hancornia speciosa Gomes (Apocynaceae), popularly known as “mangabeira,” has been used in folk medicine to treat inflammatory disorders, hypertension, dermatitis, diabetes, liver diseases and gastric disorders. Although the ethnobotany indicates that its fruits can be used for the treatment of ulcers and inflammatory disorders, only few studies have been conducted to prove such biological activities. This study investigated the anti-inflammatory properties of the aqueous extract of the fruits of H. speciosa Gomes as well as its bioactive compounds using in vivo experimental models.

Methods

The bioactive compounds were identified by High Performance Liquid Chromatography coupled with diode array detector (HPLC-DAD) and Liquid Chromatography coupled with Mass Spectrometry (LC-MS). The anti-inflammatory properties were investigated through in vivo tests, which comprised xylene-induced ear edema, carrageenan-induced peritonitis and zymosan-induced air pouch. The levels of IL-1β, IL-6, IL-12 and TNF-α were determined using ELISA.

Results

Rutin and chlorogenic acid were identified in the extract as the main secondary metabolites. In addition, the extract as well as rutin and chlorogenic acid significantly inhibited the xilol-induced ear edema and also reduced the cell migration in both carrageenan-induced peritonitis and zymosan-induced air pouch models. Reduced levels of cytokines were also observed.

Conclusion

This is the first study that demonstrated the anti-inflammatory activity of the extract of H. speciosa fruits against different inflammatory agents in animal models, suggesting that its bioactive molecules, especially rutin and chlorogenic acid are, at least in part, responsible for such activity. These findings support the widespread use of Hancornia speciosa in popular medicine and demonstrate that its aqueous extract has therapeutical potential for the development of herbal drugs with anti-inflammatory properties.

PAC1R agonist maxadilan enhances hADSC viability and neural differentiation potential

Pituitary adenylate cyclase‐activating polypeptide (PACAP) is a structurally endogenous peptide with many biological roles. However, little is known about its presence or effects in human adipose‐derived stem cells (hADSCs). In this study, the expression of PACAP type I receptor (PAC1R) was first confirmed in hADSCs. Maxadilan, a specific agonist of PAC1R, could increase hADSC proliferation as determined by Cell Counting Kit‐8 and cell cycle analysis and promote migration as shown in wound‐healing assays. Maxadilan also showed anti‐apoptotic activity in hADSCs against serum withdrawal‐induced apoptosis based on Annexin V/propidium iodide analysis and mitochondrial membrane potential assays. The anti‐apoptotic effects of maxadilan correlated with the down‐regulation of Cleaved Caspase 3 and Caspase 9 as well as up‐regulation of Bcl‐2. The chemical neural differentiation potential could be enhanced by maxadilan as indicated through quantitative PCR, Western blot and cell morphology analysis. Moreover, cytokine neural redifferentiation of hADSCs treated with maxadilan acquired stronger neuron‐like functions with higher voltage‐dependent tetrodotoxin‐sensitive sodium currents, higher outward potassium currents and partial electrical impulses as determined using whole‐cell patch clamp recordings. Maxadilan up‐regulated the Wnt/β‐catenin signalling pathway associated with dimer‐dependent activity of PAC1R, promoting cell viability that was inhibited by XAV939, and it also activated the protein kinase A (PKA) signalling pathway associated with ligand‐dependent activity of PAC1R, enhancing cell viability and neural differentiation potential that was inhibited by H‐89. In summary, these results demonstrated that PAC1R is present in hADSCs, and maxadilan could enhance hADSC viability and neural differentiation potential in neural differentiation medium.

The therapeutic potential of novel anti-migraine acute therapies

INTRODUCTION

Migraine is a highly disabling neurovascular disorder. 'The complex and multifactorial properties of migraine pathogenesis provide the opportunity to identify new therapeutic targets from a wide range of receptors.

AREAS COVERED

In this editorial, the authors focus on future pharmacological interventions for acute migraine including: 5-HT receptors and their agonists, calcitonin gene-related peptide receptors and their antagonists, PAC1 receptors and their antagonists, glutamate receptors and some of their antagonists as well as transient receptor potential channels and their antagonists. The authors also discuss preventative treatments for migraine that are currently in development.

EXPERT OPINION

Future pharmaceutical research that looks at the well-known mechanisms involved in the pathophysiology of migraine should aim to overcome the existing limitations of each pharmacological class and their side effects. There has lately been particular interest in the role of glutamate receptors, particularly metabotropic glutamate receptors, in the pathophysiology of migraine. These receptors may be potentially viable drug targets for migraine in the future.