Melatonin in experimental seizures and epilepsy

Revealing Melatonin's Mysteries: Receptors, Signaling Pathways, and Therapeutics Applications

Melatonin (5-methoxy-acetyl tryptamine) is a sleep-inducing hormone, and the pineal gland produces it in response to the circadian clock of darkness. In the body, MT1 and MT2 receptors are mostly found, having an orthosteric pocket and ligand binding determinants. Melatonin acts by binding on melatonin receptors, intracellular proteins, and orphan nuclear receptors. It inhibits adenyl cyclase and activates phospholipase C, resulting in gene expression and an intracellular alteration environment. Melatonin signaling pathways are also associated with other intracellular signaling pathways, i. e., cAMP/PKA and MAPK/ERK pathways. Relative expression of different proteins depends on the coupling profile of G protein, accounting pharmacology of the melatonin receptor bias system, and mediates action in a Gi-dependent manner. It shows antioxidant, antitumor, antiproliferative, and neuroprotective activity. Different types of melatonin agonists have been synthesized for the treatment of sleeping disorders. Researchers have developed therapeutics that target melatonin signaling, which could benefit a wide range of medical conditions. This review focuses on melatonin receptors, pharmacology, and signaling cascades; it aims to provide basic mechanical aspects of the receptor's pharmacology, melatonin's functions in cancer and neurodegenerative diseases, and any treatments and drugs designed for these diseases. This will allow a basic comparison between the receptors in question, highlighting any parallels and differences that may exist and providing fundamental knowledge about these receptors to future researchers.

Melatonin as an add-on treatment for epilepsy: A systematic review and meta-analysis

PURPOSE

Epilepsy, one severe prevalent brain disorder, primarily relies on drug treatment. However, approximately one-third of patients with epilepsy do not achieve effective control with current medications, underscoring the need for more innovative treatment approaches. Notably, melatonin has gained attention for its anti-seizure properties and favourable safety profile. This systematic review aimed to evaluate the efficacy and safety of melatonin as an add-on treatment for epilepsy.

METHODS

We searched for articles published before June 2023 in Web of Science, Cochrane Library, and PubMed. We used RevMan 5.4 software to compute relative risks (RRs) and 95 % confidence intervals (CIs). Key outcomes included total sleep time, wakefulness after sleep onset, sleep latency, seizure frequency, seizure severity, and safety. The quality of randomised controlled studies (RCTs) was assessed using the Cochrane Risk of Bias tool.

RESULTS

Of the 264 publications retrieved, 10 RCTs were included in the meta-analysis. Add-on melatonin treatment improved sleep latency (RR: 0.56; 95 %CI: 0.10-1.02; P = 0.02) and seizure severity (RR: 0.33; 95 %CI: 0.04-0.62; P = 0.03) compared with placebo treatment. Adverse events (increased headache severity in children with a history of migraines, bronchitis, ear infections, agitation, and urinary frequency) were reported in only one trial.

CONCLUSION

This systematic review found that add-on melatonin therapy improved sleep latency and seizure severity in patients with epilepsy. However, several of the included studies did not systematically assess sleep quality, seizures, and safety and lacked long-term follow-up data. Further RCTs with extended follow-up periods are required to definitively determine the efficacy and safety of melatonin.

Metabolic signatures in post-myocardial infarction heart failure, including insights into prediction, intervention, and prognosis

Heart failure (HF) is a prevalent long-term complication of myocardial infarction (MI). The incidence of post-MI HF is high, and patients with the condition have a poor prognosis. Accurate identification of individuals at high risk for post-MI HF is crucial for implementation of a protective and ideally personalized strategy to prevent fatal events. Post-MI HF is characterized by adverse cardiac remodeling, which results from metabolic changes in response to long-term ischemia. Moreover, various risk factors, including genetics, diet, and obesity, can influence metabolic pathways in patients. This review focuses on the metabolic signatures of post-MI HF that could serve as non-invasive biomarkers for early identification in high-risk populations. We also explore how metabolism participates in the pathophysiology of post-MI HF. Furthermore, we discuss the potential of metabolites as novel targets for treatment of post-MI HF and as biomarkers for prognostic evaluation. It is expected to provide valuable suggestions for the clinical prevention and treatment of post-MI HF from a metabolic perspective.

Safety and efficacy of melatonin supplementation as an add-on treatment for infantile epileptic spasms syndrome: A randomized, placebo-controlled, double-blind trial

This was a prospective, randomized, double-blind, single-center placebo-controlled trial to assess the efficacy and safety of melatonin as an add-on treatment for infantile epileptic spasms syndrome (IESS). Participants aged 3 months to 2 years with a primary diagnosis of IESS were recruited and assigned to two groups in a 1:1 ratio. Both treatment groups received a combination of adrenocorticotrophic hormone (ACTH) and magnesium sulfate (MgSO4 ) for 2 weeks, and the treatment group also received melatonin (3 mg) between 20:00 and 21:00 daily, 0.5-1 h before bedtime. The study's primary endpoint was the average reduction rate in spasm frequency assessed by seizure diaries. Secondary endpoints included assessment of the response rate, EEG hypsarrhythmia (Kramer score), and psychomotor development (Denver Developmental Screening Test, DDST). Sleep quality was assessed by using the Brief Infant Sleep Questionnaire (BISQ), the Infant Sleep Assessment Scale (ISAS), and actigraphy. Safety parameters were also evaluated. Statistical analyses were conducted on intention-to-treat and per-protocol populations. The trial is registered at Clinicaltrials.gov (ChiCTR2000036208). Out of 119 screened patients, 70 were randomized and 66 completed treatments. In the intention-to-treat population, there were no significant differences in the average percentage reduction of spasm frequency (median [interquartile range, IQR: Q3-Q1], 100% [46.7%] vs. 66.7% [55.3%], p = .288), the 3-day response rate (51.4% vs. 37.1%, p = .229), the 28-day response rate (42.9% vs. 28.6%, p = .212), EEG Kramer scores (2 [3.5] vs. 2 [3], p = .853), or DDST comprehensive months (5 [2.5] vs. 6 [6], p = .239) between the melatonin (n = 35) and placebo (n = 35) groups. However, caregivers reported improved sleep quality after melatonin treatment, with 85.7% reporting regular sleep compared to 42.9% with placebo (42.9%, p < .001). The melatonin group had lower ISAS scores in 4-11-month-old patients compared to the placebo (mean ± SD, 29.3 ± 4.4 vs. 35.2 ± 5.9, p < .001). Moreover, the median (IQR) value of sleep-onset latency was shortened by 6.0 (24.5) min after melatonin treatment, while that in the placebo group was extended by 3.0 (22.0) min (p = .030). The serum melatonin (6:00 h) level (pg/mL) of the children in the melatonin group after treatment was significantly higher than in the placebo group (median [IQR], 84.8 [142] vs. 17.5 [37.6], p < .001). No adverse effects related to melatonin were observed in the study, and there were no significant differences in adverse effects between the melatonin and placebo groups. Although not statistically significant, the results of this randomized clinical trial proved that melatonin supplementation, as an add-on treatment, can improve spasm control rate in the treatment of IESS. For IESS children treated with ACTH, the addition of melatonin was found to improve sleep quality, shorten sleep onset latency, and increase blood melatonin levels. Moreover, it was observed to be a safe treatment option.

On-demand electrically controlled melatonin release from PEDOT/SNP composite improves quality of chronic neural recording

Long-time and high-quality signal acquisition performance from implantable electrodes is the key to establish stable and efficient brain-computer interface (BCI) connections. The chronic performance of implantable electrodes is hindered by the inflammatory response of brain tissue. In order to solve the material limitation of biological interface electrodes, we designed sulfonated silica nanoparticles (SNPs) as the dopant of Poly (3,4-ethylenedioxythiophene) (PEDOT) to modify the implantable electrodes. In this work, melatonin (MT) loaded SNPs were incorporated in PEDOT via electrochemical deposition on nickel-chromium (Ni-Cr) alloy electrode and carbon nanotube (CNT) fiber electrodes, without affecting the acute neural signal recording capacity. After coating with PEDOT/SNP-MT, the charge storage capacity of both electrodes was significantly increased, and the electrochemical impedance at 1 kHz of the Ni-Cr alloy electrodes was significantly reduced, while that of the CNT electrodes was significantly increased. In addition, this study inspected the effect of electrically triggered MT release every other day on the quality and longevity of neural recording from implanted neural electrodes in rat hippocampus for 1 month. Both MT modified Ni-Cr alloy electrodes and CNT electrodes showed significantly higher spike amplitude after 26-day recording. Significantly, the histological studies showed that the number of astrocytes around the implanted Ni-Cr alloy electrodes was significantly reduced after MT release. These results demonstrate the potent outcome of PEDOT/SNP-MT treatment in improving the chronic neural recording quality possibly through its anti-inflammatory property.

CPEB4-CLOCK crosstalk during temporal lobe epilepsy

OBJECTIVE

Posttranscriptional mechanisms are increasingly recognized as important contributors to the formation of hyperexcitable networks in epilepsy. Messenger RNA (mRNA) polyadenylation is a key regulatory mechanism governing protein expression by enhancing mRNA stability and translation. Previous studies have shown large-scale changes in mRNA polyadenylation in the hippocampus of mice during epilepsy development. The cytoplasmic polyadenylation element-binding protein CPEB4 was found to drive epilepsy-induced poly(A) tail changes, and mice lacking CPEB4 develop a more severe seizure and epilepsy phenotype. The mechanisms controlling CPEB4 function and the downstream pathways that influence the recurrence of spontaneous seizures in epilepsy remain poorly understood.

METHODS

Status epilepticus was induced in wild-type and CPEB4-deficient male mice via an intra-amygdala microinjection of kainic acid. CLOCK binding to the CPEB4 promoter was analyzed via chromatin immunoprecipitation assay and melatonin levels via high-performance liquid chromatography in plasma.

RESULTS

Here, we show increased binding of CLOCK to recognition sites in the CPEB4 promoter region during status epilepticus in mice and increased Cpeb4 mRNA levels in N2A cells overexpressing CLOCK. Bioinformatic analysis of CPEB4-dependent genes undergoing changes in their poly(A) tail during epilepsy found that genes involved in the regulation of circadian rhythms are particularly enriched. Clock transcripts displayed a longer poly(A) tail length in the hippocampus of mice post-status epilepticus and during epilepsy. Moreover, CLOCK expression was increased in the hippocampus in mice post-status epilepticus and during epilepsy, and in resected hippocampus and cortex of patients with drug-resistant temporal lobe epilepsy. Furthermore, CPEB4 is required for CLOCK expression after status epilepticus, with lower levels in CPEB4-deficient compared to wild-type mice. Last, CPEB4-deficient mice showed altered circadian function, including altered melatonin blood levels and altered clustering of spontaneous seizures during the day.

SIGNIFICANCE

Our results reveal a new positive transcriptional-translational feedback loop involving CPEB4 and CLOCK, which may contribute to the regulation of the sleep-wake cycle during epilepsy.

Serum Levels of Neuropeptides in Epileptic Encephalopathy With Spike-and-Wave Activation in Sleep

BACKGROUND

Epileptic encephalopathy with spike-and-wave activation in sleep (EE-SWAS) is a syndrome of childhood, characterized by diffuse or generalized spike-wave activity in electroencephalography during non-rapid eye movement sleep. Neuropeptides have been demonstrated in several studies to function in the sleep-wake cycle and display convulsant and anticonvulsant features. In this study, we aimed to investigate the relationship between EE-SWAS and neuropeptides such as dynorphin, galanin, ghrelin, leptin, melatonin, and orexin.

METHODS

This multicenter study was conducted from July 2019 to January 2021. There were three groups: Group 1 contained patients with EE-SWAS. Group 2 consisted of patients with self-limited focal epilepsy of childhood (SeLFE), and group 3 was the control group. Levels of neuropeptides were compared in the sera of these three groups.

RESULTS

There were 59 children aged between four and 15 years. Group 1 contained 14 children, group 2 contained 24 children, and group 3 contained 21 children. The level of leptin is higher and the level of melatonin is lower in group 1 than in group 3 (P = 0.01 and P = 0.005, respectively). In group 3, the level of orexin was lower than in both groups 2 and 3 (P = 0.01 and P = 0.01).

CONCLUSIONS

These data show that the level of leptin was higher and the level of melatonin was lower in patients with EE-SWAS than in the control group. Furthermore, patients with EE-SWAS had lower orexin levels than both the control group and patients with SeLFE. Further research is required to understand the potential role of these neuropeptides in the pathophysiology of EE-SWAS.

The interaction between circadian rhythm and epilepsy

Evidence about the interaction between circadian rhythms (CR) and epilepsy has been expanded with the application of advanced detection technology. An adequate understanding of how circadian system and epilepsy interact with each other could contribute to more accurate seizure prediction as well as rapid development of potential treatment timed to specific phases of CR. In this review, we present the reciprocal relationship between CR and epileptic activities from aspects of sleep effect, genetic modulation and brain biochemistry. It has been found that sleep-wake patterns, circadian timing systems and multidien rhythms have essential roles in seizure activities and interictal epileptiform discharge (IED). For instance, specific distribution patterns of seizures and IED have been reported, i.e., lighter non-rapid eye movement (NREM) sleep stage (stage 2) induces seizures while deeper NREM sleep stage (stage 3) activates IEDs. Furthermore, the epilepsy type, seizure type and seizure onset zone can significantly affect the rhythms of seizure occurrence. Apart from the common seizure types, several specific epilepsy syndromes also have a close correlation with sleep-wakefulness patterns. Sleep influences the epilepsy rhythm, and conversely, epilepsy alters the sleep rhythm through multiple pathways. Clock genes accompanied by two feedback loops of regulation have an important role in cortical excitability and seizure occurrence, which may be involved in the mTORopathy. The suprachiasmatic nuclei (SCN) has a rhythm of melatonin and cortisol secretion under the circadian pattern, and then these hormones can feed back into a central oscillator to affect the SCN-dependent rhythms, leading to variable but prominent influence on epilepsy. Furthermore, we discuss the precise predictive algorithms and chronotherapy strategies based on different temporal patterns of seizure occurrence for patients with epilepsy, which may offer a valuable indication for non-invasive closed-loop treatment system. Optimization of the time and dose of antiseizure medications, and resynchronization of disturbed CR (by hormone therapy, light exposure, ketogenic diet, novel small molecules) would be beneficial for epileptic patients in the future. Before formal clinical practice, future large-scale studies are urgently needed to assist prediction and treatment of circadian seizure activities and address unsolved restrictions.

Morin offsets PTZ-induced neuronal degeneration and cognitive decrements in rats: The modulation of TNF-α/TNFR-1/RIPK1,3/MLKL/PGAM5/Drp-1, IL-6/JAK2/STAT3/GFAP and Keap-1/Nrf-2/HO-1 trajectories

Morin is a bioactive flavonoid with prominent neuroprotective potentials, however, its impact on epilepsy-provoked cognitive dysregulations has not been revealed. Hence, the present investigation aims to divulge the potential anticonvulsant/neuroprotective effects of morin in rats using a pentylenetetrazole (PTZ)-induced kindling model with an emphasis on the possible signaling trajectories involved. Kindling was induced using a sub-convulsive dose of PTZ (35 mg/kg, i.p.), once every other day for 25 days (12 injections). The expression of targeted biomarkers and molecular signals were examined in hippocampal tissues by ELISA, Western blotting, immunohistochemistry, and histopathology. Contrary to PTZ effects, administration of morin (10 mg/kg, i.p., from day 15 of PTZ injection to the end of the experiment) significantly reduced the severity of seizures coupled with a delay in kindling acquisition. It also preserved hippocampal neurons, and diminished astrogliosis to counteract cognitive deficits, exhibited by the enhanced performance in MWM and PA tests. These favorable impacts of morin were mediated via the abrogation of the PTZ-induced necroptotic changes and mitochondrial fragmentation proven by the suppression of p-RIPK-1/p-RIPK-3/p-MLKL and PGAM5/Drp-1 cues alongside the enhancement of caspase-8. Besides, morin inhibited the inflammatory cascade documented by the attenuation of the pro-convulsant receptor/cytokines TNFR-1, TNF-α, I L-1β, and IL-6 and the marked reduction of hippocampal IL-6/p-JAK2/p-STAT3/GFAP cue. In tandem, morin signified its anti-oxidant capacity by lowering the hippocampal contents of MDA, NOX-1, and Keap-1 with the restoration of the impaired Nrf-2/HO-1 pathway. Together, these versatile neuro-modulatory effects highlight the promising role of morin in the management of epilepsy.

Melatonin as an Antiepileptic Molecule: Therapeutic Implications via Neuroprotective and Inflammatory Mechanisms

Epilepsy is a result of unprovoked, uncontrollable, and repetitive outburst of abnormal and excessive electrical discharges, known as seizures, in the neurons. Epilepsy is a devastating neurological condition that affects 70 million people globally. Unfortunately, only two-thirds of epilepsy patients respond to antiepileptic drugs while others become drug resistant and may be more prone to epilepsy comorbidities such as SUDEP. Oxidative stress, mitochondrial dysfunction, imbalance in the excitatory and inhibitory neurotransmitters, and neuroinflammation are some of the common pathologies of neurological disorders and epilepsy. Studies suggests that melatonin, a pineal hormone that governs sleep-wake cycles, may be neuroprotective against neurological disorders and thus may be translated as an antiepileptic as well. Melatonin has been shown to be an antioxidant, antiexcitotoxic, and anti-inflammatory hormone/molecule in neurodegenerative diseases, which may contribute to its antiepileptic and neuroprotective properties in epilepsy as well. In addition, melatonin has evidently been shown to play a regulatory role in the cardiorespiratory system and sleep-wake cycles, which may have positive implications toward epilepsy associated comorbidities, such as SUDEP. However, studies investigating the changes in melatonin release due to epilepsy and melatonin's antiepileptic role have been inconclusive and scarce, respectively. Thus, this comprehensive review aims to summarize and elucidate the potential role of melatonin in the pathogenesis of epilepsy and its comorbidities, in hopes to develop new diagnostic and therapeutic approaches that will improve the lives of epileptic patients, particularly those who are drug resistant.

Melatonin Exerts Anti-Inflammatory, Antioxidant, and Neuromodulatory Effects That Could Potentially Be Useful in the Treatment of Vertigo

The acute phase of vertigo involves multiple neurotransmitters, inflammatory mediators, and products of oxidative stress. The vestibular pathway has multiple melatonin receptors distributed along its path, both centrally and peripherally. In addition, melatonin has been shown to be a powerful antioxidant and anti-inflammatory agent against factors related to vertigo, such as Bax/caspases, interleukins, and chemokines. Likewise, it exerts central GABAergic, antidopaminergic, and anti-migraine functions and regulates sympathetic activity in a similar way to the drugs classically used in acute vestibular crisis. In this review, the role of melatonin as a potential treatment of the acute phase of vertigo is discussed.

Melatonin for an obese child with MC4R gene variant showing epilepsy and disordered sleep: A case report

BACKGROUND

Abnormalities in the melanocortin receptor 4 (MC4R) gene often lead to obesity, but are rarely associated with other conditions such as epilepsy and sleep disorder.

CASE SUMMARY

Here, we present a case of a male obese child with a heterozygous variant in MC4R (c.494G>A, p.Arg165Gln) inherited from his father, who presented with disordered sleep and abnormal facial movements. Examination through melatonin rhythm testing and electroencephalography led to a diagnosis of sleep disorder and epilepsy, as his melatonin rhythm was markedly distorted and the electroencephalography revealed epileptic discharges. He received treatment with an antiepileptic drug; however, the therapy was ineffective and the sleep disorder appeared to be deteriorating. Subsequently, we initiated adjuvant treatment with melatonin. Upon re-examination, his body mass index had decreased, the sleep disturbance had resolved, and his seizures were well controlled. Electro-encephalography review was normal, and a typical melatonin rhythm was restored.

CONCLUSION

We concluded that, in addition to causing obesity, abnormalities in the MC4R gene may contribute to the development of sleep disorders and epilepsy, and that melatonin can be used as an adjuvant therapy to alleviate these symptoms.

Dysregulation of REV-ERBα impairs GABAergic function and promotes epileptic seizures in preclinical models

To design potentially more effective therapies, we need to further understand the mechanisms underlying epilepsy. Here, we uncover the role of Rev-erbα in circadian regulation of epileptic seizures. We first show up-regulation of REV-ERBα/Rev-erbα in brain tissues from patients with epilepsy and a mouse model. Ablation or pharmacological modulation of Rev-erbα in mice decreases the susceptibility to acute and chronic seizures, and abolishes diurnal rhythmicity in seizure severity, whereas activation of Rev-erbα increases the animal susceptibility. Rev-erbα ablation or antagonism also leads to prolonged spontaneous inhibitory postsynaptic currents and elevated frequency in the mouse hippocampus, indicating enhanced GABAergic signaling. We also identify the transporters Slc6a1 and Slc6a11 as regulators of Rev-erbα-mediated clearance of GABA. Mechanistically, Rev-erbα promotes the expressions of Slc6a1 and Slc6a11 through transcriptional repression of E4bp4. Our findings propose Rev-erbα as a regulator of synaptic function at the crosstalk between pathways regulating the circadian clock and epilepsy.

Melatonin ameliorates diabetes-induced brain injury in rats

Diabetic brain is a serious complication of diabetes, and it is associated with oxidative stress and neuronal injury. This study investigated the protective effect of melatonin (MLT) on diabetes-induced brain injury. A rat model of type 2 diabetes mellitus was produced by intraperitoneal injection of nicotinamide 100 mg/kg, followed by intraperitoneal injection of streptozotocin 55 mg/kg. The diabetic rats were orally administered MLT 10 mg/kg of body weight for 15 days. MLT remarkably downregulated serum glucose levels. It also improved levels of the lipid peroxidation product 4-hydroxynonenal, improved levels of antioxidants including glutathione, glutathione peroxidase and glutathione reductase in the brains of the diabetic rats, and this is indicative of the antioxidant potential of MLT. MLT also prevented increase in homocysteine, amyloid-β42 and tau levels in diabetic rats, and this suggests that it can reduce the risk of dementia. This is associated with reduction in the levels of the dopamine, serotonin, and glutamate and is indicative of the regulatory effect of MLT on neurotransmitters. Treatment with MLT improved diabetes-induced structural alteration in the hippocampus and cerebral cortex. MLT significantly reduced caspase-3 and Bax as well as significantly increase Bcl-2 protein and GFAP-positive astrocytes indicating its anti-apoptotic effect. MLT showed remarkable ameliorative effect against biochemical and molecular alterations in the brains of diabetic rats most likely through its antioxidant property.

Real-Time Fast Scan Cyclic Voltammetry Detection and Quantification of Exogenously Administered Melatonin in Mice Brain

Melatonin (MT) has been recently considered an excellent candidate for the treatment of sleep disorders, neural injuries, and neurological diseases. To better investigate the actions of MT in various brain functions, real-time detection of MT concentrations in specific brain regions is much desired. Previously, we have demonstrated detection of exogenously administered MT in anesthetized mouse brain using square wave voltammetry (SWV). Here, for the first time, we show successful detection of exogenous MT in the brain using fast scan cyclic voltammetry (FSCV) on electrochemically pre-activated carbon fiber microelectrodes (CFEs). In vitro evaluation showed the highest sensitivity (28.1 nA/μM) and lowest detection limit (20.2 ± 4.8 nM) ever reported for MT detection at carbon surface. Additionally, an extensive CFE stability and fouling assessment demonstrated that a prolonged CFE pre-conditioning stabilizes the background, in vitro and in vivo, and provides consistent CFE sensitivity over time even in the presence of a high MT concentration. Finally, the stable in vivo background, with minimized CFE fouling, allows us to achieve a drift-free FSCV detection of exogenous administered MT in mouse brain over a period of 3 min, which is significantly longer than the duration limit (usually < 90 s) for traditional in vivo FSCV acquisition. The MT concentration and dynamics measured by FSCV are in good agreement with SWV, while microdialysis further validated the concentration range. These results demonstrated reliable MT detection using FSCV that has the potential to monitor MT in the brain over long periods of time.

The Instigation of the Associations Between Melatonin, Circadian Genes, and Epileptic Spasms in Infant Rats

Background: Infantile spasm (IS) is one of the most common catastrophic epilepsy syndromes in infancy characterized by epileptic spasm. While adrenocorticotropic hormone (ACTH) is the first-line treatment for IS, it is evident that the seizures associated with IS exhibit a clear circadian rhythm; however, the precise mechanisms underlying such seizures remain unclear. Melatonin is an important amine hormone and is regulated by circadian rhythm. Circadian proteins, especially Aryl Hydrocarbon Receptor Nuclear Trasnslocator-like Protein (ARNTL or BMAL1) and Circadian Locomotor Output Cycles Kaput (CLOCK), and their target proteins Period Circadian Regulator 1 (PER1), Period Circadian Regulator 2 (PER2), Cryptochrome 1 (CRY1), and Cryptochrome 2 (CRY2), play key roles in circadian rhythm. This study explored the relationships between melatonin, genes associated with circadian rhythm, and epileptic spasm.

Materials and Methods: Eighteen female rats were mated with nine male rats and 16 became pregnant. Twelve pregnant rats were subjected to prenatal stress by forced swimming in cold water from the day of conception. Rat pups produced by stressed mothers received an intraperitoneal injection of N-methyl-D-aspartate (NMDA) on the 13th day after birth and were divided into four groups: NMDA (15 mg/kg), NMDA+ACTH (20 IU/kg), NMDA+melatonin (55 mg/kg), and NMDA+ACTH+melatonin (n = 36/group). Offspring from four dams that were not subjected to prenatal stress were used as controls. We then recorded latency and the frequency of flexion seizures. All offspring were sacrificed on the 14th day after birth and CLOCK, BMAL1, PER1, PER2, CRY1, and CRY2 expression was analyzed by western blotting, immunohistochemistry, and immunofluorescence.

Results: NMDA induced spasm-like symptoms in rats. ACTH and melatonin significantly increased seizure latency and significantly reduced the frequency of seizures (P < 0.05). CLOCK, BMAL1, PER1, PER2, CRY1, and CRY2 expression was significantly lower in the NMDA group than the controls (P < 0.05). ACTH significantly increased the expression of CLOCK, BAML1, PER1, and CRY1 (P < 0.05) and melatonin significantly increased the expression of CLOCK, BMAL1, PER1, PER2, CRY1, and CRY2 (P < 0.05) compared with those of the NMDA group. There were no significant differences in the expression of BMAL1, CRY2, PER1, and PER2 when compared between the NMDA+ACTH+melatonin and control groups (P > 0.05).

Conclusion: ACTH and melatonin significantly increased the expression of circadian genes and improved NMDA-induced seizures. The anticonvulsant effects of ACTH and melatonin are likely to involve regulation of the expression of these genes.

The role of melatonin and its analogues in epilepsy

Extensive research has gone into proposing a promising link between melatonin administration and attenuation of epileptic activity, the majority of which suggest its propensity as an antiseizure with antioxidant and neuroprotective properties. In the past few years, a number of studies highlighting the association of the melatonergic ligands with epilepsy have also emerged. In this context, our review is based on discussing the recent studies and various mechanisms of action that the said category of drugs exhibit in the context of being therapeutically viable antiseizure drugs. Our search revealed several articles on the four major drugs i.e. melatonin, agomelatine, ramelteon and piromelatine along with other melatonergic agonists like tasimelteon and TIK-301. Our review is suggestive of antiseizure effects of both melatonin and its analogues; however, extensive research work is still required to study their implications in the treatment of persons with epilepsy. Further evaluation of melatonergic signaling pathways and mechanisms may prove to be helpful in the near future and might prove to be a significant advance in the field of epileptology.

Homostachydrine is a Xenobiotic Substrate of OCTN1/SLC22A4 and Potentially Sensitizes Pentylenetetrazole-Induced Seizures in Mice

Understanding of the underlying mechanism of epilepsy is desired since some patients fail to control their seizures. The carnitine/organic cation transporter OCTN1/SLC22A4 is expressed in brain neurons and transports food-derived antioxidant ergothioneine (ERGO), L-carnitine, and spermine, all of which may be associated with epilepsy. This study aimed to clarify the possible association of this transporter with epileptic seizures. In both pentylenetetrazole (PTZ)-induced acute seizure and kindling models, ocnt1 gene knockout mice (octn1^-/-) showed lower seizure scores compared with wild-type mice. Up-regulation of the epilepsy-related genes, c-fos and Arc, and the neurotrophic factor BDNF following PTZ administration was observed in the hippocampus of wild-type, but not octn1^-/- mice. To find the OCTN1 substrate associated with the seizure, untargeted metabolomics analysis using liquid chromatography-quadrupole time-of-flight mass spectrometry was conducted on extracts from the hippocampus, frontal cortex, and plasma of both strains, leading to the identification of a plant alkaloid homostachydrine as a compound present in a lower concentration in octn1^-/- mice. OCTN1-mediated uptake of deuterium-labeled homostachydrine was confirmed in OCTN1-transfected HEK293 cells, suggesting that this compound is a substrate of OCTN1. Homostachydrine administration increased PTZ-induced acute seizure scores and the expression of Arc in the hippocampus and that of Arc, Egr1, and BDNF in the frontal cortex. Conversely, administration of the OCTN1 substrate/inhibitor ERGO inhibited PTZ-induced kindling and reduced the plasma homostachydrine concentration. Thus, these results suggest that OCTN1 is at least partially associated with PTZ-induced seizures, which is potentially deteriorated by treatment with homostachydrine, a newly identified food-derived OCTN1 substrate.

Dietary Melatonin Protects Against Behavioural, Metabolic, Oxidative, and Organ Morphological Changes in Mice that are Fed High-Fat, High- Sugar Diet

BACKGROUND

Metabolic syndrome is a complex pattern of disorders that occur jointly and is associated with an increased risk of cardiovascular and cerebrovascular disease. Therefore the need for more-efficient options of treatment has become imperative.

OBJECTIVE

This study examined the effect of dietary-melatonin in the management of behavioural, metabolic, antioxidant, and organ changes due to high-fat/high-sugar (HFHS) diet-induced metabolic syndrome in mice.

METHODS

Mice were randomly assigned into five groups of ten animals each. Groups were normal control [fed standard diet (SD)], HFHS control, and 3 groups of melatonin incorporated into HFHS at 2.5, 5, and 10 mg/kg of feed. Mice were fed for seven weeks, and body weight was assessed weekly. Open-field behaviours, radial-arm, and Y-maze spatial memory were scored at the end of the experimental period. Twenty-four hours after the last behavioural test, blood was taken for estimation of blood glucose levels after an overnight fast. Animals were then euthanised, and blood was taken for estimation of plasma insulin, leptin, and adiponectin levels, and serum lipid profile. The liver, kidneys, and brain were excised and processed for general histology, while homogenates of the liver and whole brain were used to assess oxidative stress parameters.

RESULTS

Results showed that dietary melatonin (compared to HFHS diet) was associated with a decrease in body weight, food intake, and novelty-induced behaviours; and an increase in spatial-working memory scores. A decrease in glucose, insulin, leptin, and malondialdehyde levels; and an increase in adiponectin levels and superoxide dismutase activity were also observed. Histomorphological/ histomorphometric examination revealed evidence of organ injury with HFHS diet, and varying degrees of amelioration with melatonin-supplemented diet.

CONCLUSION

In conclusion, dietary melatonin supplementation may have beneficial effects in the management of the metabolic syndrome.

Quinazoline and phthalazine derivatives as novel melatonin receptor ligands analogues of agomelatine

For further development of successors of Agomelatine through modulation of its pharmacokinetic properties, we report herein the design, synthesis and pharmacological results of a new family of melatonin receptor ligands. Issued from the introduction of quinazoline and phthalazine scaffolds carrying an ethyl amide lateral chain and a methoxy group as bioisosteric ligands analogues of previously developed Agomelatine. The biological activity of the prepared analogues was compared with that of Agomelatine. Quinazoline and phthalazine rings proved to be a versatile scaffold for easy feasible MT₁ and MT₂ ligands. Potent agonists with sub-micromolar binding affinity were obtained. However, the presence of two nitrogen atoms resulted in compounds with lower affinity for both MT₁ and MT₂, in comparison with the parent compound, balanced by the exhibition of good pharmacokinetic properties.

Comparison Between Efficacy of Melatonin and Diazepam for Prevention of Recurrent Simple Febrile Seizures: A Randomized Clinical Trial

OBJECTIVES

We evaluated the efficacy and safety of oral melatonin compared with oral diazepam for prevention of recurrent simple febrile seizures.

METHODS

This prospective randomized clinical trial included 60 children aged six to 50 months with recurrent simple febrile seizures who attended the pediatric neurology clinic in Tanta University Hospital. Children were randomly allocated into two groups: the first group (30 children) received oral melatonin 0.3 mg/kg/8 hours, whereas the other group (30 children) received oral diazepam 1 mg/kg/day divided into three doses. Both melatonin and diazepam were given only during the febrile illness, started at the onset of the fever for 48 to 72 hours. Patients were followed up for six months. The primary outcome was recurrence of febrile seizures and the secondary outcome was occurrence of adverse effect related to melatonin or diazepam.

RESULTS

The recurrence rate of febrile seizures was 17% (5/30) in the melatonin group and 37% (11/30) in the diazepam group. There was no significant difference between the two groups (P = 0.08) (95% confidence interval -0.025 to 0.42). Both melatonin and diazepam have significantly reduced recurrence of febrile seizures (P < 0.001). Adverse effects were reported in 13.3% and 23.3% of the children taking melatonin and diazepam, respectively. No serious side effects were reported with melatonin use. Sedation and dizziness were the main side effects reported in children receiving oral diazepam.

CONCLUSIONS

Our data suggest that melatonin, administered at the onset of a febrile illness, may effectively reduce the likelihood of recurrent simple febrile seizures. No serious side effects were encountered.

Dampening of neurotransmitter action: molecular similarity within the melatonin structure

OBJECTIVES

Melatonin initiates physiologic and therapeutic responses in various tissues through binding to poorly defined MT receptors regulated by G-proteins and purine nucleotides. Melatonin's interaction with other G-protein regulated receptors, including those of serotonin, is unclear. This study explores the potential for the interaction of melatonin with nucleotide and receptor ligand structures.

METHODS

The study uses a computational program to investigate relative molecular similarity by the comparative superimposition and quantitative fitting of molecular structures to adenine and guanine nucleotide templates.

RESULTS

A minimum energy melatonin conformer replicates the nucleotide fits of ligand structures that regulate Gαi and Gαq proteins via serotonin, dopamine, opioid, α-adrenoceptor, and muscarinic receptor classes. The same conformer also replicates the nucleotide fits of ligand structures regulating K+ and Ca2+ ion channels. The acyl-methoxy distance within the melatonin conformer matches a carbonyl-hydroxyl distance in guanine nucleotide.

CONCLUSION

Molecular similarity within the melatonin and ligand structures relates to the established effects of melatonin on cell receptors regulated by purine nucleotides in cell signal transduction processes. Pharmacologic receptor promiscuity may contribute to the widespread effects of melatonin.

Chronobiology of limbic seizures: Potential mechanisms and prospects of chronotherapy for mesial temporal lobe epilepsy

Mesial Temporal Lobe Epilepsy (mTLE) characterized by progressive development of complex partial seizures originating from the hippocampus is the most prevalent and refractory type of epilepsy. One of the remarkable features of mTLE is the rhythmic pattern of occurrence of spontaneous seizures, implying a dependence on the endogenous clock system for seizure threshold. Conversely, circadian rhythms are affected by epilepsy too. Comprehending how the circadian system and seizures interact with each other is essential for understanding the pathophysiology of epilepsy as well as for developing innovative therapies that are efficacious for better seizure control. In this review, we confer how the temporal dysregulation of the circadian clock in the hippocampus combined with multiple uncoupled oscillators could lead to periodic seizure occurrences and comorbidities. Unraveling these associations with additional research would help in developing chronotherapy for mTLE, based on the chronobiology of spontaneous seizures. Notably, differential dosing of antiepileptic drugs over the circadian period and/or strategies that resynchronize biological rhythms may substantially improve the management of seizures in mTLE patients.

Abnormal Hippocampal Melatoninergic System: A Potential Link between Absence Epilepsy and Depression-Like Behavior in WAG/Rij Rats?

Absence epilepsy and depression are comorbid disorders, but the molecular link between the two disorders is unknown. Here, we examined the role of the melatoninergic system in the pathophysiology of spike and wave discharges (SWDs) and depression-like behaviour in the Wistar Albino Glaxo from Rijswijk (WAG/Rij) rat model of absence epilepsy. In WAG/Rij rats, SWD incidence was higher during the dark period of the light-dark cycle, in agreement with previous findings. However, neither pinealectomy nor melatonin administration had any effect on SWD incidence, suggesting that the melatoninergic system was not involved in the pathophysiology of absence-like seizures. Endogenous melatonin levels were lower in the hippocampus of WAG/Rij rats as compared to non-epileptic control rats, and this was associated with higher levels of melatonin receptors in the hippocampus, but not in the thalamus. In line with the reduced melatonin levels, cell density was lower in the hippocampus of WAG/Rij rats and was further reduced by pinealectomy. As expected, WAG/Rij rats showed an increased depression-like behaviour in the sucrose preference and forced swim tests, as compared to non-epileptic controls. Pinealectomy abolished the difference between the two strains of rats by enhancing depression-like behaviour in non-epileptic controls. Melatonin replacement displayed a significant antidepressant-like effect in both WAG/Rij and control rats. These findings suggest that a defect of hippocampal melatoninergic system may be one of the mechanisms underlying the depression-like phenotype in WAG/Rij rats and that activation of melatonin receptors might represent a valuable strategy in the treatment of depression associated with absence epilepsy.

Research progress on the role of melatonin and its receptors in animal reproduction: A comprehensive review

Melatonin and its receptors play a crucial role in the regulation of the animal reproductive process, primarily in follicular development. However, the role that melatonin performs in regulating hormones related with reproduction remains unclear. Melatonin and its receptors are present both in female and male animals' organs, such as ovaries, heart, brain and liver. Melatonin regulates ovarian actions and is a key mediator of reproductive actions. Melatonin has numerous effects on animal reproduction, such as protection of gametes and embryos, response to clock genes, immune-neuroendocrine, reconciliation of seasonal variations in immune function, and silence or blockage of genes. The growth ratio of reproductive illnesses in animals has raised a remarkable concern for the government, animal caretakers and farm managers. In order to resolve this challenging issue, it is very necessary to conduct state-of-the-art research on melatonin and its receptors because melatonin has considerable physiognomies. This review article presents a current contemporary research conducted by numerous researchers from the entire world on the role of melatonin and its receptors in animal reproduction, from the year 1985 to the year 2017. Furthermore, this review shows scientific research challenges related to melatonin receptors and their explanations based on the findings of 172 numerous research articles, and also represents significant proficiencies of melatonin in order to show enthusiastic study direction for animal reproduction researchers.

The Mutual Interaction Between Sleep and Epilepsy on the Neurobiological Basis and Therapy

BACKGROUND

Sleep and epilepsy are mutually related in a complex, bidirectional manner. However, our understanding of this relationship remains unclear.

RESULTS

The literatures of the neurobiological basis of the interactions between sleep and epilepsy indicate that non rapid eye movement sleep and idiopathic generalized epilepsy share the same thalamocortical networks. Most of neurotransmitters and neuromodulators such as adenosine, melatonin, prostaglandin D2, serotonin, and histamine are found to regulate the sleep-wake behavior and also considered to have antiepilepsy effects; antiepileptic drugs, in turn, also have effects on sleep. Furthermore, many drugs that regulate the sleep-wake cycle can also serve as potential antiseizure agents. The nonpharmacological management of epilepsy including ketogenic diet, epilepsy surgery, neurostimulation can also influence sleep.

CONCLUSION

In this paper, we address the issues involved in these phenomena and also discuss the various therapies used to modify them.

d-Leucine: Evaluation in an epilepsy model

BACKGROUND

Current medicines do not provide sufficient seizure control for nearly one-third of patients with epilepsy. New options are needed to address this treatment gap. We recently found that the atypical amino acid d-leucine protected against acutely-induced seizures in mice, but its effect in chronic seizures has not been explored. We hypothesized that d-leucine would protect against spontaneous recurrent seizures. We also investigated whether mice lacking a previously-described d-leucine receptor (Tas1R2/R3) would be protected against acutely-induced seizures.

METHODS

Male FVB/NJ mice were subjected to kainic acid-induced status epilepticus and monitored by video-electroencephalography (EEG) (surgically implanted electrodes) for 4weeks before, during, and after treatment with d-leucine. Tas1R2/R3 knockout mice and controls underwent the maximal electroshock threshold (MES-T) and 6-Hz tests.

RESULTS

There was no difference in number of calendar days with seizures or seizure frequency with d-leucine treatment. In an exploratory analysis, mice treated with d-leucine had a lower number of dark cycles with seizures. Tas1R2/R3 knockout mice had elevated seizure thresholds in the MES-T test but not the 6-Hz test.

CONCLUSIONS

d-Leucine treatment was ineffective against chronic seizures after kainic acid-induced status epilepticus, but there was some efficacy during the dark cycle. Because d-leucine is highly concentrated in the pineal gland, these data suggest that d-leucine may be useful as a tool for studying circadian patterns in epilepsy. Deletion of the Tas1R2/R3 receptor protected against seizures in the MES-T test and, therefore, may be a novel target for treating seizures.

Novel biomarkers of metabolic dysfunction is autism spectrum disorder: potential for biological diagnostic markers

Autism spectrum disorder (ASD) is a neurodevelopmental disorder that is behaviorally defined by social and communication impairments and restricted interests and repetitive behaviors. There is currently no biomarkers that can help in the diagnosis. Several studies suggest that mitochondrial dysfunction is commonly involved in ASD pathophysiology, but standard mitochondrial biomarkers are thought to be very variable. In the present study we examine a wide variety of plasma biomarkers of mitochondrial metabolism and the related abnormalities of oxidative stress and apoptosis in 41 ASD patients assessed for ASD severity using the Childhood Autism Rating Scales and 41 non-related age and sex matched healthy controls. Our findings confirm previous studies indicating abnormal mitochondrial and related biomarkers in children with ASD including pyruvate, creatine kinase, Complex 1, Glutathione S-Transferase, glutathione and Caspase 7. As a novel finding, we report that lactate dehydrogenase is abnormal in children with ASD. We also identified that only the most severe children demonstrated abnormalities in Complex 1 activity and Glutathione S-Transferase. Additionally, we find that several biomarkers could be candidates for differentiating children with ASD and typically developing children, including Caspase 7, gluthatione and Glutathione S-Transferase by themselves and lactate dehydrogenase and Complex I when added to other biomarkers in combination. Caspase 7 was the most discriminating biomarker between ASD patients and healthy controls suggesting its potential use as diagnostic marker for the early recognition of ASD pathophysiology. This study confirms that several mitochondrial biomarkers are abnormal in children with ASD and suggest that certain mitochondrial biomarkers can differentiate between ASD and typically developing children, making them possibly useful as a tool to diagnosis ASD and identify ASD subgroups.

Effects of agomelatine on pentylenetetrazole-induced kindling, kindling-associated oxidative stress, and behavioral despair in mice and modulation of its actions by luzindole and 1-(m-chlorophenyl) piperazine

In view of well-evidenced antiepileptic effects of melatonin and few reports of anticonvulsant action of agomelatine, the present study investigated whether agomelatine protects against pentylenetetrazole (PTZ)-induced kindling in mice and kindling-associated oxidative stress, depression, and impairment of spatial memory. In order to explore whether effects are mediated by melatonergic or serotonergic mechanisms, 1-(m-chlorophenyl) piperazine (mCPP), selective 5HT2c receptor agonist and luzindole, melatonergic receptor antagonist, were taken as pharmacological tools. In view of few hepatotoxic reports on agomelatine, the study evaluated effects on hepatic enzyme levels. Swiss strain albino mice were injected with PTZ (25mg/kg, i.p.) once every two days for 5weeks to induce kindling. The effects of agomelatine (10mg/kg, p.o.) alone and in combination with luzindole (2.5mg/kg, i.p.) or mCPP (7mg/kg, i.p.) on seizure severity during induction and % incidence of animals kindled at the end of 5weeks were recorded. Modified forced swim test was used for studying depression-like behavior while spontaneous alternation behavior was used for studying effects on spatial memory. Serum AST and ALT concentrations, cortical and hippocampal malondialdehyde, and reduced glutathione were measured. Agomelatine 10mg/kg, p.o. effectively delayed development of kindling, reduced seizure severity, and decreased % incidence. Luzindole reversed the protective effects of agomelatine while mCPP failed to show such a reversal, indicating melatonergic (and not serotonergic) mechanisms in the observed effects. Agomelatine also showed antioxidant effects that can partially contribute to its anticonvulsant action. In addition, it alleviated PTZ-kindling-associated behavioral despair and favorably modulated liver enzymes. Its effects on improvement of kindling-associated spatial memory could possibly be related to its effects on locomotor activity. Agomelatine, thus, could be explored as an adjunct to antiepileptic drugs for seizure control and for alleviating epilepsy-associated depression.

Melatonin Alleviates the Epilepsy-Associated Impairments in Hippocampal LTP and Spatial Learning Through Rescue of Surface GluR2 Expression at Hippocampal CA1 Synapses

Epilepsy-associated cognitive impairment is common, and negatively impacts patients' quality of life. However, most antiepileptic drugs focus on the suppression of seizures, and fewer emphasize treatment of cognitive dysfunction. Melatonin, an indolamine synthesized primarily in the pineal grand, is reported to be neuroprotective against several central nervous system disorders. In this study, we investigated whether melatonin could reverse cognitive dysfunction in lithium-pilocarpine treated rats. Chronic treatment with melatonin (8 mg/kg daily for 15 days) after induction of status epilepticus significantly alleviated seizure severity, reduced neuronal death in the CA1 region of the hippocampus, improved spatial learning (as measured by the Morris water maze test), and reversed LTP impairments, compared to vehicle treatment. Furthermore, we found that melatonin rescued the decreased surface levels of GluR2 in the CA1 region observed in epilepsy, which might be the underlying mechanism of the neuroprotective and synapse-modulating function of melatonin. Our study provides experimental evidence for the possible clinical utility of melatonin as an adjunctive therapy to prevent epilepsy-associated cognitive impairments.

Monoaminergic Mechanisms in Epilepsy May Offer Innovative Therapeutic Opportunity for Monoaminergic Multi-Target Drugs

A large body of experimental and clinical evidence has strongly suggested that monoamines play an important role in regulating epileptogenesis, seizure susceptibility, convulsions, and comorbid psychiatric disorders commonly seen in people with epilepsy (PWE). However, neither the relative significance of individual monoamines nor their interaction has yet been fully clarified due to the complexity of these neurotransmitter systems. In addition, epilepsy is diverse, with many different seizure types and epilepsy syndromes, and the role played by monoamines may vary from one condition to another. In this review, we will focus on the role of serotonin, dopamine, noradrenaline, histamine, and melatonin in epilepsy. Recent experimental, clinical, and genetic evidence will be reviewed in consideration of the mutual relationship of monoamines with the other putative neurotransmitters. The complexity of epileptic pathogenesis may explain why the currently available drugs, developed according to the classic drug discovery paradigm of "one-molecule-one-target," have turned out to be effective only in a percentage of PWE. Although, no antiepileptic drugs currently target specifically monoaminergic systems, multi-target directed ligands acting on different monoaminergic proteins, present on both neurons and glia cells, may represent a new approach in the management of seizures, and their generation as well as comorbid neuropsychiatric disorders.

Evaluation of Plasma Melatonin Levels in Children With Afebrile and Febrile Seizures

BACKGROUND

Melatonin modulates central nervous system neuronal activity. We compared the melatonin levels of patients with febrile and afebrile seizures during and after seizure with those of healthy controls.

METHODS

We enrolled 59 individuals with afebrile and febrile seizures (mean age, 6.09 ± 4.46 years) and 28 age-, sex-, and weight-matched healthy children. Melatonin levels were measured near the time of a seizure (0 to 1 hour) and at 12 and 24 hours post-seizure, and control melatonin levels were measured from a single venous blood sample.

RESULTS

Plasma melatonin levels increased during seizures in the study group (P < 0.001). Post-seizure plasma melatonin levels were significantly lower in the study group than in the control group (P < 0.05). Plasma melatonin levels did not differ between patients with afebrile seizures who had and had not used antiepileptic drugs. Daytime (8 AM to 8 PM) and nighttime (8 PM to 8 AM) post-seizure melatonin levels were not significantly different.

CONCLUSIONS

Melatonin levels were lower in pediatric patients prone to seizures than in healthy children and increased during seizures. Further research is needed to test the role of melatonin in the pathophysiology and treatment of epilepsy.

GIRK Channels Mediate the Nonphotic Effects of Exogenous Melatonin

Melatonin supplementation has been used as a therapeutic agent for several diseases, yet little is known about the underlying mechanisms by which melatonin synchronizes circadian rhythms. G-protein signaling plays a large role in melatonin-induced phase shifts of locomotor behavior and melatonin receptors activate G-protein-coupled inwardly rectifying potassium (GIRK) channels in Xenopus oocytes. The present study tested the hypothesis that melatonin influences circadian phase and electrical activity within the central clock in the suprachiasmatic nucleus (SCN) through GIRK channel activation. Unlike wild-type littermates, GIRK2 knock-out (KO) mice failed to phase advance wheel-running behavior in response to 3 d subcutaneous injections of melatonin in the late day. Moreover, in vitro phase resetting of the SCN circadian clock by melatonin was blocked by coadministration of a GIRK channel antagonist tertiapin-q (TPQ). Loose-patch electrophysiological recordings of SCN neurons revealed a significant reduction in the average action potential rate in response to melatonin. This effect was lost in SCN slices treated with TPQ and SCN slices from GIRK2 KO mice. The melatonin-induced suppression of firing rate corresponded with an increased inward current that was blocked by TPQ. Finally, application of ramelteon, a potent melatonin receptor agonist, significantly decreased firing rate and increased inward current within SCN neurons in a GIRK-dependent manner. These results are the first to show that GIRK channels are necessary for the effects of melatonin and ramelteon within the SCN. This study suggests that GIRK channels may be an alternative therapeutic target for diseases with evidence of circadian disruption, including aberrant melatonin signaling.

SIGNIFICANCE STATEMENT

Despite the widespread use of melatonin supplementation for the treatment of sleep disruption and other neurological diseases such as epilepsy and depression, no studies have elucidated the molecular mechanisms linking melatonin-induced changes in neuronal activity to its therapeutic effects. Here, we used behavioral and electrophysiological techniques to address this scientific gap. Our results show that melatonin and ramelteon, a potent and clinically relevant melatonin receptor agonist, significantly affect the neurophysiological function of suprachiasmatic nucleus neurons through activation of G-protein-coupled inwardly rectifying potassium (GIRK) channels. Given the importance of GIRK channels for neuronal excitability (with >600 publications on these channels to date), our study should generate broad interest from neuroscientists in fields such as epilepsy, addiction, and cognition.

Diurnal and seasonal occurrence of febrile seizures

BACKGROUND

Febrile seizures are the most common seizures in children, but their pathogenesis remains unknown. Some studies have suggested an association between the light-dependent secretion of melatonin and the occurrence of febrile seizures. The diurnal and seasonal occurrence of febrile seizures could clarify the role daylight plays in febrile seizures.

METHODS

In Finland, summer days are long and bright and winter days are short and dark. We evaluated the diurnal and seasonal occurrence of the first febrile seizures in 461 children and adjusted them according to the epidemiology of the febrile episodes in a population-based study of 1522 children.

RESULTS

The first febrile seizure most often occurred in the evening, peaking between 6 and 10 PM (31%), and least often at night, in the early morning hours between 2 and 6 AM (8%) (P < 0.001). This diurnal pattern repeated itself in different seasons according to variance in daylight duration. Febrile seizures occurred irregularly throughout the year, most frequently in winter, concurrently with the febrile episodes, and least frequently in summer; this seasonal variation in the occurrence of febrile seizures disappeared however when adjusted for the number of febrile events.

CONCLUSIONS

We found clear diurnal and seasonal variations in the occurrence of febrile seizures, even though they did not follow the amount of daylight. Our findings do not support the hypothesis that the diurnal and seasonal variation of daylight explains the occurrence of febrile seizures. Moreover, febrile events associated strongly with the occurrence of febrile seizures.

Melatonin improves sleep in children with epilepsy: a randomized, double-blind, crossover study

OBJECTIVE

Insomnia, especially maintenance insomnia, is widely prevalent in epilepsy. Although melatonin is commonly used, limited data address its efficacy. We performed a randomized, double-blind, placebo-controlled, crossover study to identify the effects of melatonin on sleep and seizure control in children with epilepsy.

METHODS

Eleven prepubertal, developmentally normal children aged 6-11 years with epilepsy were randomized by a software algorithm to receive placebo or a 9-mg sustained release (SR) melatonin formulation for four weeks, followed by a one-week washout and a four-week crossover condition. The pharmacy performed blinding; patients, parents, and study staff other than a statistician were blinded. The primary outcomes were sleep onset latency and wakefulness after sleep onset (WASO) measured on polysomnography. The secondary outcomes included seizure frequency, epileptiform spike density per hour of sleep on electroencephalogram (EEG), and reaction time (RT) measures on psychomotor vigilance task (PVT). Statistical tests appropriate for crossover designs were used for the analysis.

RESULTS

Data were analyzed from 10 subjects who completed the study. Melatonin decreased sleep latency (mean difference, MD, of 11.4 min and p = 0.02) and WASO (MD of 22 min and p = 0.04) as compared to placebo. No worsening of spike density or seizure frequency was seen. Additionally, slow-wave sleep duration and rapid eye movement (REM) latency were increased with melatonin and REM sleep duration was decreased. These changes were statistically significant. Worsening of headache was noted in one subject with migraine on melatonin.

CONCLUSION

SR melatonin resulted in statistically significant decreases in sleep latency and WASO. No clear effects on seizures were observed, but the study was too small to allow any conclusions to be drawn in this regard.

Circadian profile of salivary melatonin secretion and its concentration after epileptic seizure in patients with drug-resistant epilepsy--preliminary report

BACKGROUND

The results of a few previous studies assessing melatonin concentration in epileptic patient are ambiguous. This study aimed at: (1) comparing the circadian profile of salivary melatonin excretion in epileptic patients with that in healthy subjects and with circadian frequency profile of seizures and (2) assessing the effect of epileptic seizure upon salivary melatonin concentration.

METHODS

The study included thirty patients suffering from drug-resistant epilepsy aged from 22 to 45 years (mean age 37.17, SD ± 10.25). All subjects had their saliva taken in order to determine melatonin concentration and its circadian excretion profile performed every 4h. Additionally, saliva samples were collected in order to assess concentration of melatonin directly after epileptic seizure and 2h later.

RESULTS

The circadian profile of melatonin secretion in epileptic patients did not differ significantly from a profile in healthy subjects. Epileptic women showed statistically higher average salivary melatonin concentration at 2a.m., 6a.m. and 10a.m., compared to epileptic men; this may be related to lower age average of women as well as to their different hormonal profile.

CONCLUSION

The significantly higher salivary melatonin concentration at 6a.m. in patients with diurnal seizures (occurring mainly in the morning) may suggest proconvulsive effect of this hormone. Epileptic seizure did not lead to significantly elevated salivary melatonin concentration. Epileptogenic effect of melatonin might be corroborated by significantly elevated salivary melatonin levels directly after nocturnal tonic-clonic seizure which affected patients with highest concentration of this hormone at 2a.m. These observations would need confirmation based on studies of larger groups of epileptic patients.

Melatonin inhibits voltage-sensitive Ca(2+) channel-mediated neurotransmitter release

Melatonin is involved in various neuronal functions such as circadian rhythmicity and thermoregulation. Melatonin has a wide range of pharmacologically effective concentration levels from the nanomolar to millimolar levels. Recently, the antiepileptic effect of high dose melatonin has been the focus of clinical studies; however, its detailed mechanism especially in relation to neurotransmitter release and synaptic transmission remains unclear. We studied the effect of melatonin at high concentrations on the neurotransmitter release by monitoring norepinephrine release in PC12 cells, and excitatory postsynaptic potential in rat hippocampal slices. Melatonin inhibits the 70mM K(+)-induced Ca(2+) increase at millimolar levels without effect on bradykinin-triggered Ca(2+) increase in PC12 cells. Melatonin (1mM) did not affect A2A adenosine receptor-evoked cAMP production, and classical melatonin receptor antagonists did not reverse the melatonin-induced inhibitory effect, suggesting G-protein coupled receptor independency. Melatonin inhibits the 70mM K(+)-induced norepinephrine release at a similar effective concentration range in PC12 cells. We confirmed that melatonin (100µM) inhibits excitatory synaptic transmission of the hippocampal Schaffer collateral pathway with the decrease in basal synaptic transmission and the increase in paired pulse ratio. These results show that melatonin inhibits neurotransmitter release through the blocking of voltage-sensitive Ca(2+) channels and suggest a possible mechanism for the antiepileptic effect of melatonin.

Treatment with melatonin after status epilepticus attenuates seizure activity and neuronal damage but does not prevent the disturbance in diurnal rhythms and behavioral alterations in spontaneously hypertensive rats in kainate model of temporal lobe epilepsy

Melatonin is involved in the control of circadian and seasonal rhythmicity, possesses potent antioxidant activity, and exerts a neuroprotective and anticonvulsant effect. Spontaneously hypertensive rats (SHRs) are widely accepted as an experimental model of essential hypertension with hyperactivity, deficient sustained attention, and alterations in circadian autonomic profiles. The purpose of the present study was to determine whether melatonin treatment during epileptogenesis can prevent the deleterious consequences of status epilepticus (SE) in SHRs in the kainate (KA) model of temporal lobe of epilepsy (TLE). Spontaneous recurrent seizures (SRSs) were EEG- and video-recorded during and after the treatment protocol. Melatonin (10mg/kg diluted in drinking water, 8weeks) increased the seizure-latent period, decreased the frequency of SRSs, and attenuated the circadian rhythm of seizure activity in SHRs. However, melatonin was unable to affect the disturbed diurnal rhythms and behavioral changes associated with epilepsy, including the decreased anxiety level, depression, and impaired spatial memory. Melatonin reduced neuronal damage specifically in the CA1 area of the hippocampus and piriform cortex and decreased hippocampal serotonin (5-HT) levels both in control and epileptic SHRs. Although long-term melatonin treatment after SE shows a potential to attenuate seizure activity and neuronal loss, it is unable to restore epilepsy-associated behavioral abnormalities in SHRs.

Effects of agomelatine on oxidative stress in the brain of mice after chemically induced seizures

Agomelatine is a novel antidepressant drug with melatonin receptor agonist and 5-HT(2C) receptor antagonist properties. We analyzed whether agomelatine has antioxidant properties. Antioxidant activity of agomelatine (25, 50, or 75 mg/kg, i.p.) or melatonin (50 mg/kg) was investigated by measuring lipid peroxidation levels, nitrite content, and catalase activities in the prefrontal cortex, striatum, and hippocampus of Swiss mice pentylenetetrazole (PTZ) (85 mg/kg, i.p.), pilocarpine (400 mg/kg, i.p.), picrotoxin (PTX) (7 mg/kg, i.p.), or strychnine (75 mg/kg, i.p.) induced seizure models. In the pilocarpine-induced seizure model, all dosages of agomelatine or melatonin showed a significant decrease in TBARS levels and nitrite content in all brain areas when compared to controls. In the strychnine-induced seizure model, all dosages of agomelatine and melatonin decreased TBARS levels in all brain areas, and agomelatine at low doses (25 or 50 mg/kg) and melatonin decreased nitrite contents, but only agomelatine at 25 or 50 mg/kg showed a significant increase in catalase activity in three brain areas when compared to controls. Neither melatonin nor agomelatine at any dose have shown no antioxidant effects on parameters of oxidative stress produced by PTX- or PTZ-induced seizure models when compared to controls. Our results suggest that agomelatine has antioxidant activity as shown in strychnine- or pilocarpine-induced seizure models.

Pineal melatonin level disruption in humans due to electromagnetic fields and ICNIRP limits

The International Agency for Research on Cancer (IARC) classifies electromagnetic fields (EMFs) as 'possibly carcinogenic' to humans that might transform normal cells into cancer cells. Owing to high utilisation of electricity in day-to-day life, exposure to power-frequency (50 or 60 Hz) EMFs is unavoidable. Melatonin is a natural hormone produced by pineal gland activity in the brain that regulates the body's sleep-wake cycle. How man-made EMFs may influence the pineal gland is still unsolved. The pineal gland is likely to sense EMFs as light but, as a consequence, may decrease the melatonin production. In this study, more than one hundred experimental data of human and animal studies of changes in melatonin levels due to power-frequency electric and magnetic fields exposure were analysed. Then, the results of this study were compared with the International Committee of Non-Ionizing Radiation Protection (ICNIRP) limit and also with the existing experimental results in the literature for the biological effect of magnetic fields, in order to quantify the effects. The results show that this comparison does not seem to be consistent despite the fact that it offers an advantage of drawing attention to the importance of the exposure limits to weak EMFs. In addition to those inconsistent results, the following were also observedfrom this work: (i) the ICNIRP recommendations are meant for the well-known acute effects, because effects of the exposure duration cannot be considered and (ii) the significance of not replicating the existing experimental studies is another limitation in the power-frequency EMFs. Regardless of these issues, the above observation agrees with our earlier study in which it was confirmed that it is not a reliable method to characterise biological effects by observing only the ratio of AC magnetic field strength to frequency. This is because exposure duration does not include the ICNIRP limit. Furthermore, the results show the significance of disruption of melatonin due to exposure to weak EMFs, which may possibly lead to long-term health effects in humans.

Prophylactic treatment with melatonin after status epilepticus: effects on epileptogenesis, neuronal damage, and behavioral changes in a kainate model of temporal lobe epilepsy

Melatonin is a potent antioxidant which showed anticonvulsant activities both in experimental and clinical studies. In the present study, we examined the effect of melatonin treatment (10mg/kg/day, diluted in drinking water, 8 weeks) during epileptogenesis on the consequences of a kainate (KA)-induced status epilepticus (SE) in rats. Melatonin increased the latency in the appearance of spontaneous recurrent seizures (SRSs) and decreased their frequency only during the treatment period. The behavioral alterations associated with hyperactivity, depression-like behavior during the light phase, and deficits in hippocampus-dependent working memory were positively affected by melatonin treatment in rats with epilepsy. Melatonin reduced the neuronal damage in the CA1 area of the hippocampus and piriform cortex and recovered the decrease of hippocampal serotonin (5-HT) level in rats with epilepsy. Taken together, long-term melatonin treatment after SE was unable to suppress the development of epileptogenesis. However, it showed a potential in reducing some of the deleterious alterations that develop during the chronic epileptic state in a diurnal phase-dependent mode.