Day-night variations in melatonin secretion by the pineal gland during febrile and epileptic convulsions in children

Development of a prediction nomogram model of recurrent febrile seizures in pediatric children

The purpose of this study is to develop a prediction nomogram of recurrent febrile seizures in pediatric children based on the identified predictors for developing recurrent febrile seizures. This is a retrospective observational study. The medical records of 320 febrile seizure-afflicted children admitted to Zhoushan Women and Children Hospital from March 2019 to January 2023 were retrospectively reviewed. Children were divided into the recurrent febrile seizures group and the non-recurrent febrile seizures group. The predictors of recurrent febrile seizures were identified by univariate and multivariate analyses. A prediction nomogram model was developed via R software. The performance of the nomogram was internally validated to assess the model's discrimination and consistency, and decision curve analysis was employed to assess clinical utility. There were 41 out of 320 cases that had recurrent febrile seizures during the observation period, with a 12.81% prevalence rate of recurrent febrile seizures. The predictors of recurrent febrile seizures were young age at the first febrile seizures, a family history of febrile seizures in a first-degree relative, diurnal variation of initial febrile seizures occurrence, gender, and a low level of C-reactive protein. The area under the receiver operating characteristic curve of the nomogram is 0.795 (95% confidence interval: 0.720-0.871). Calibration plots and the result of the Hosmer-Lemeshow test (P = 0.472) reveal satisfactory consistency. Decision curve analysis showed a significant net benefit of the nomogram.

CONCLUSIONS

The prediction nomogram model demonstrates good performance and clinical utility, which would be a convenient tool for the detection of children in pediatrics with high-risk recurrent febrile seizures. It is useful for pediatric medical staff to provide early medical interventions and family counseling.

WHAT IS KNOWN

• A proportion of children experience recurrences of febrile seizures. • Recognition of risk factors for recurrent FS in pediatrics would be useful for the prediction of risk probabilities and help provide tailored counseling and follow-up.

WHAT IS NEW

• A nomogram model is developed for risk prediction of recurrent febrile seizures in this study, which would be a convenient risk prediction tool in pediatrics. • The predictor of diurnal variation of recurrent febrile seizures is with new ideas.

Cycles in epilepsy

Epilepsy is among the most dynamic disorders in neurology. A canonical view holds that seizures, the characteristic sign of epilepsy, occur at random, but, for centuries, humans have looked for patterns of temporal organization in seizure occurrence. Observations that seizures are cyclical date back to antiquity, but recent technological advances have, for the first time, enabled cycles of seizure occurrence to be quantitatively characterized with direct brain recordings. Chronic recordings of brain activity in humans and in animals have yielded converging evidence for the existence of cycles of epileptic brain activity that operate over diverse timescales: daily (circadian), multi-day (multidien) and yearly (circannual). Here, we review this evidence, synthesizing data from historical observational studies, modern implanted devices, electronic seizure diaries and laboratory-based animal neurophysiology. We discuss advances in our understanding of the mechanistic underpinnings of these cycles and highlight the knowledge gaps that remain. The potential clinical applications of a knowledge of cycles in epilepsy, including seizure forecasting and chronotherapy, are discussed in the context of the emerging concept of seizure risk. In essence, this Review addresses the broad question of why seizures occur when they occur.

Can chronopharmacology improve the therapeutic management of neurological diseases?

The importance of circadian rhythm dysfunctions in the pathophysiology of neurological diseases has been highlighted recently. Chronopharmacology principles imply that tailoring the timing of treatments to the circadian rhythm of individual patients could optimize therapeutic management. According to these principles, chronopharmacology takes into account the individual differences in patients' clocks, the rhythmic changes in the organism sensitivity to therapeutic and side effects of drugs, and the predictable time variations of disease. This review examines the current literature on chronopharmacology of neurological diseases focusing its scope on epilepsy, Alzheimer and Parkinson diseases, and neuropathic pain, even if other neurological diseases could have been analyzed. While the results of the studies discussed in this review point to a potential therapeutic benefit of chronopharmacology in neurological diseases, the field is still in its infancy. Studies including a sufficiently large number of patients and measuring gold standard markers of the circadian rhythmicity are still needed to evaluate the beneficial effect of administration times over the 24-hour day but also of clock modulating drugs.

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.

Diurnal occurrence of complex febrile seizure and their severity in pediatric patients needing hospitalization

Several studies describing the diurnal occurrence of febrile seizures have reported greater seizure frequency early or late in the evening relative to midnight or early morning. However, no articles have reported on the diurnal occurrence of complex febrile seizure. Moreover, no studies have addressed the relationship between seizure severity and diurnal occurrence. We retrospectively evaluated complex febrile seizures in 462 children needing hospitalization, and investigated the relationship between severity and diurnal occurrence according to four categorized time periods (morning, afternoon, evening, and night). Our study showed that complex febrile seizures occurred most often in the evening, peaking around 18:00 (18:00-18:59), and least often at night (02:00-02:59). In addition, the frequency with which patients developed status epilepticus or needed anticonvulsant treatments was also lower during the night. However, the seizure duration and the proportion of the patients who needed anticonvulsant treatment were the same among the four time periods. Furthermore, we compared three subclasses (repeated episodes of convulsions, focal seizures, and prolonged seizures (≧15min)), two of the complex features (focal seizures and prolonged seizures), and all complex features among the four time periods. However, they were the same among the four time periods. Taken together, our data indicate that although the severity of seizures was stable over a 24-hour period, the occurrence of seizures in our cohort of pediatric patients with complex febrile seizures requiring hospitalization was highest in the evening and lowest at night.

Melatonin and Angelman Syndrome: Implications and Mathematical Model of Diurnal Secretion

The main aim of the study was to compare the melatonin rhythms in subjects with Angelman syndrome (n = 9) and in children with (n = 80) and without (n = 40) epilepsy (nonepileptic patients diagnosed with peripheral nerve palsies, myopathy, and back pain) using our mathematical model of melatonin circadian secretion. The characteristics describing the diurnal hormone secretion such as minimum melatonin concentration, release amplitude, phase shift of melatonin release, and sleep duration as well as the dim light melatonin onset (DLMO) of melatonin secretion and the γ shape parameter allow analyzing the fit and deducing about how much the measured melatonin profile differs from a physiological bell-shaped secretion. The estimated sleep duration and phase shift of melatonin release as well as the DMLO offsets at 25% and 50% relative thresholds are the key characteristic of Angelman syndrome children. As revealed from the γ shape parameter, the melatonin secretion profiles are disturbed in majority of the AG subjects revealing rather a triangular course instead of the bell-like one.

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.

Neuropsychological consequences of sleep disturbance in children with epilepsy

A growing body of research reveals strong relationships between sleep disturbance, sleep architecture, and neuropsychological functioning in children. Children with epilepsy experience numerous neuropsychological comorbidities, including cognitive deficiencies and emotional/behavioral difficulties; thus, it is reasonable to consider the moderating role of sleep in this population. This review summarizes findings involving the prevalence and characteristics of sleep problems often experienced by children with epilepsy. The complex and bidirectional relationship between sleep and seizure frequency is discussed. Research pertaining to the relationship between sleep disturbance and daytime cognition as well as behavior reveals a substantial association between these variables. Clinically relevant practices related to the assessment and treatment of sleep-related complications are reviewed, and directions for further research involving intervention and assessment are also reviewed.

Melatonin in Epilepsy: A New Mathematical Model of Diurnal Secretion

Purpose. The main objective of the study was to create a mathematical model that describes the melatonin circadian secretion and, then the functionality of the model was tested by a comparison of the melatonin secretions in children with and without epilepsy. Material and Methods. The patients were divided into the epilepsy group (EG, n = 52) and the comparison group (CG, n = 30). The melatonin level was assessed by a radioimmunoassay method. The diurnal melatonin secretion was described using a nonlinear least squares method. Spearman's rank correlation coefficient was chosen to estimate the dependence of the acquired data. The model reproduces blood concentration profiles and its parameters were statistically analyzed using the Mann-Whitney-Wilcoxon test and logistic regression. Results. The correlation analysis performed for the EG and CG groups showed moderate correlations between age and the melatonin secretion model parameters. Patients with epilepsy are characterized by an increased phase shift of melatonin release.

Chronopharmacology of anti-convulsive therapy

Approximately one-third of patients with epilepsy continue to have seizures despite antiepileptic therapy. Many seizures occur in diurnal, sleep/wake, circadian, or even monthly patterns. The relationship between biomarkers and state changes is still being investigated, but early results suggest that some of these patterns may be related to endogenous circadian patterns whereas others may be related to wakefulness and sleep or both. Chronotherapy, the application of treatment at times of greatest seizure susceptibility, is a technique that may optimize seizure control in selected patients. It may be used in the form of differential dosing, as preparations designed to deliver sustained or pulsatile drug delivery or in the form of 'zeitgebers' that shift endogenous rhythms. Early trials in epilepsy suggest that chronopharmacology may provide improved seizure control compared with conventional treatment in some patients. The present article reviews chronopharmacology in the treatment of epilepsy as well as future treatment avenues.

Melatonin secretion in children with epilepsy

This study examined melatonin (MLT) system in children with epilepsy. Diurnal patterns of salivary MLT, urinary metabolite 6-sulphatoxymelatonin, core body temperature, pulse and blood pressure were measured in 51 children with epilepsy (6.6-17.9 years) and 29 comparison children (5.5-17.3 years). The children with epilepsy preserved MLT and other circadian rhythms. In nine children with epilepsy (17.6%), peak salivary MLT concentrations were very high. There were no associations between MLT secretion/excretion parameters (diurnal profile, peak nocturnal concentrations, area under the time curve, duration of elevated concentrations, acrophase) and seizure characteristics (time, type of seizures, antiepileptic medications). The study observations are important for understanding of the MLT system in epilepsy and for exploring the potential for seizure treatment with melatonin.

The interaction of melatonin and agmatine on pentylenetetrazole-induced seizure threshold in mice

Melatonin, the major hormone produced by the pineal gland, has a number of functions in mammals, for example, its function as an anticonvulsant. Agmatine, a biogenic amine formed by decarboxylation of L-arginine by arginine decarboxylase, also has anticonvulsant effects. This study investigated the effect of the interaction of melatonin and agmatine on seizure susceptibility in the mouse model of pentylenetetrazole (PTZ)-induced clonic seizures. Further, the researchers investigated the involvement of melatonin receptors in this interaction using luzindole, a ML(1/2) receptor antagonist and prazosin, a ML(3) receptor antagonist. Melatonin, at 40 and 80 mg/kg, and agmatine, at 10 and 20mg/kg, exerted anticonvulsant effects. Luzindole, at 1.25 and 2.5mg/kg, or prazosin, at 0.5mg/kg, did not change the seizure threshold as compared with that of vehicle-treated mice. The anticonvulsant effect of melatonin (40 and 80 mg/kg) was prevented by luzindole (2.5mg/kg) (P<0.001) but not prazosin (0.5mg/kg), indicating the possible involvement of ML(1/2) receptors in the anticonvulsant effect of melatonin. Agmatine (5mg/kg) significantly increased the anticonvulsant effect of both the noneffective dose (20mg/kg) (P<0.05) and the effective dose (80 mg/kg) (P<0.001) of melatonin. Luzindole (2.5mg/kg), but not prazosin (0.5mg/kg), decreased the anticonvulsant effect of agmatine (20mg/kg) (P<0.05). Luzindole (2.5mg/kg), but not prazosin (0.5mg/kg), also decreased the seizure threshold when agmatine (5mg/kg) was administered before melatonin (20mg/kg); the decrease was significant compared with that of the group that received only agmatine and melatonin (P<0.001). In conclusion, melatonin and agmatine exhibit an additive effect in decreasing pentylenetetrazole-induced seizure threshold in mice, probably through ML(1/2) receptors.

Psychosocial dwarfism: psychopathological aspects and putative neuroendocrine markers

There exists an extensive terminology for defining the situation of children who, in varying circumstances, suffer from affective deprivation (AD), within an unsatisfactory family situation or in institutions. Nevertheless, the neuroendocrine mechanisms (if they exist) determining it have yet to be identified. Our objective was to determine if specific neuroendocrine markers, all of them previously implicated in affective disorders, could be modified, and in which sense, in affective deprivation syndrome of the child. For this purpose, we studied three separate groups of children: (1) control group (CG); (2) children suffering from AD; and (3) children with non-organic failure to thrive (NOFT). In every case, we studied the serum levels of melatonin, serotonin, β-endorphins and adrenocorticotropic hormone (ACTH); and kynurenine pathway tryptophan metabolites (both during the day and at night). Significantly, there was a conspicuous reduction in the levels of each of the neuroendocrine markers (melatonin, serotonin, β-endorphins and ACTH) in the group suffering from affective deficiency, a diminution which was even more noticeable in the group of patients presenting delayed growth. Furthermore, as also occurs in other affective disorders, there were corresponding modifications in the metabolisation of tryptophan. We report the existence of neuroendocrine mechanisms that are associated with the above-mentioned clinical manifestations in these patients, mechanisms that may underlie the close connection existing between AD syndrome and the cause of NOFT. These data suggest that the AD syndrome and NOFT comprise a single process, but one with a different evolutionary continuum of psychosocial dwarfism.

Normalization of the sleep-wake pattern and melatonin and 6-sulphatoxy-melatonin levels after a therapeutic trial with melatonin in children with severe epilepsy

This study evaluated the sleep-wake pattern, plasma melatonin levels and the urinary excretion of its metabolite, 6-sulphatoxy-melatonin among children with severe epileptic disorders, before and after a therapeutic trial with melatonin. Ten paediatric patients, suffering from severe epileptic disorders, were selected and given a nightly dose of 3 mg of a placebo, for 1 wk; for the next 3 months, the placebo was replaced with a nightly dose of 3 mg of melatonin. At the end of each treatment period, the urinary excretion of 6-sulphatoxy-melatonin (for the intervals 09.00 - 21:00 hr or 21:00-09:00 hr) and plasma levels of melatonin (recorded at 01:00, 05:00, 09:00, 13:00, 17:00 and 21:00 hr) were recorded, over a period of 24 hr; an actigraph record was also kept. Sleep efficiency among patients who received melatonin was significantly higher than among those given the placebo, with fewer night-time awakenings. Periodic plasma melatonin levels were regained and a better control gained of convulsive episodes, in that the number of seizures decreased. We conclude that melatonin is a good regulator of the sleep-wake cycle for paediatric patients suffering from severe epilepsy, moreover, it to a better control of convulsive episodes.

The pilocarpine model of epilepsy: what have we learned?

The systemic administration of a potent muscarinic agonist pilocarpine in rats promotes sequential behavioral and electrographic changes that can be divided into 3 distinct periods: (a) an acute period that built up progressively into a limbic status epilepticus and that lasts 24 h, (b) a silent period with a progressive normalization of EEG and behavior which varies from 4 to 44 days, and (c) a chronic period with spontaneous recurrent seizures (SRSs). The main features of the SRSs observed during the long-term period resemble those of human complex partial seizures and recurs 2-3 times per week per animal. Therefore, the pilocarpine model of epilepsy is a valuable tool not only to study the pathogenesis of temporal lobe epilepsy in human condition, but also to evaluate potential antiepileptogenic drugs. This review concentrates on data from pilocarpine model of epilepsy.

The circadian rhythm and its interaction with human epilepsy: a review of literature

Knowledge on the interaction between circadian rhythm and human epilepsy is relatively poor, although if it exists, this interaction may be of value for better knowledge of pathophysiology and for timing of diagnostic procedures and therapy. It appears that human seizure occurrence may have 24-h rhythmicity, depending on the origin. These findings are endorsed by animal studies. Rats placed in constant darkness showed spontaneous limbic seizures occurring in an endogenously mediated circadian pattern. More studies are available on the influence of epilepsy on circadian rhythms. Significant differences in chronotypes between patients with different epilepsy syndromes have been found and numerous studies have described influences of epilepsy and seizures on sleep. In contrast, knowledge on (core) body temperature and clock genes in patients is minimal. Reduced heart rate variability and changed hormone levels, which are under the influence of the biological clock, have been observed in people with epilepsy. In short, large gaps in the knowledge about the interaction of circadian rhythm and human epilepsy still remain. Proposals for studies in this borderline area between the biological clock and epilepsy will be discussed.

A single generalized seizure alters the amplitude, but not phase, of the circadian activity rhythm of the hamster

People with epilepsy exhibit high rates of sleep disturbances. In many cases, these sleep disruptions appear to be related to the occurrence of the seizures themselves. Changes in sleep structure may reflect underlying changes in the circadian clock, as circadian rhythms of locomotor activity, body temperature, and hormone release are disrupted following a seizure. The present study was designed to determine if a single generalized seizure could alter the phase and waveform of the circadian rhythm of wheel-running behavior in the Syrian hamster. Animals were housed in constant darkness, and were administered either a sham treatment or a maximal electroconvulsive shock at one of three time-points: 6 h before activity onset, 1 h after activity onset, or 6 h after activity onset. Seizures at all of these phases did not significantly affect the phase of the circadian activity rhythm. The circadian locomotor activity levels were significantly attenuated following seizures at all three phases. This attenuation was prominent over the 24 h following the seizure, and was also evident over the three post-seizure days. These data suggest that while seizures do not affect phase, they may alter the amplitude of the circadian clock. Because the amplitude of the circadian clock affects sleep quality, these findings suggest one mechanism by which persistent seizures may decrease the quality of sleep in patients with epilepsy.

Cardiovascular protective effect of melatonin in sudden unexpected death in epilepsy: A hypothesis

Epilepsy is the most common neurological disorder, approximately 1% of the population worldwide have epilepsy. Moreover, sudden unexpected death in epilepsy (SUDEP) is the most important direct epilepsy-related cause of death. Information concerning risk factors for SUDEP is conflicting, but potential risk factors include: age, early onset of epilepsy, duration of epilepsy, uncontrolled seizures, seizure frequency, AED number and winter temperatures. Additionally, the cause of SUDEP is still unknown; however, the most commonly suggested mechanisms are cardiac abnormalities during and between seizures. Furthermore, the evidence from the last 10 years suggests that melatonin has an important role in the epileptogenesis process and influences the cardiovascular system as well. The positive effect of melatonin has been demonstrated against different convulsive stimuli in several rodents, including seizures induced by pentylenetetrazole kainate, glutamate, maximal electrical shock and electrically kindled stimulation of amygdala. Clinical studies have also demonstrated a positive role of melatonin on the seizure frequency in children and reduced spiking activity and seizure frequency in patients with intractable epilepsy. In the rat hearts, studies in vivo and in vitro using pharmacological concentrations of melatonin confirmed an anti-arrhythmic effect of this hormone and studies in humans have been shown that chronic heart disease patients have significantly lower melatonin levels in their blood stream than do normal individuals. Thus, caution should be taken in generalization of these findings to epileptic population. Moreover, it is important to note that when dealing with intractable epilepsy that do not respond to any conventional treatment, the additional of melatonin may be evaluated. Taken together, in this paper we suggested a possible relationship between cardiac abnormalities, melatonin and SUDEP.

Melatonin enhances the anticonvulsant and proconvulsant effects of morphine in mice: Role for nitric oxide signaling pathway

Melatonin has different interactions with opioids including enhancing their analgesic effect and reversal of opioid tolerance and dependence. Opioids are known to exert dose-dependent anti- and proconvulsant effects in different experimental seizure paradigms. This study investigated the effect of melatonin on biphasic modulation of seizure susceptibility by morphine, in mouse model of pentylenetetrazole (PTZ)-induced clonic seizures. We further investigated the involvement of the nitric oxidergic pathway in this interaction, using a nitric oxide synthase inhibitor, NG-nitro-L-arginine-methyl-ester (L-NAME). Melatonin exerted anticonvulsant effect with doses as high as 40-80 mg/kg, but with a dose far bellow that amount (10 mg/kg), it potentiated both the anticonvulsant and proconvulsant effects of morphine on the PTZ-induced clonic seizures. Possible pharmacokinetic interaction of melatonin and morphine cannot be ruled out in the enhancement of two opposing effects of morphine on seizure threshold. L-NAME (1 mg/kg) reversed the anticonvulsant property of the combination of melatonin (10 mg/kg) plus morphine (0.5 mg/kg). Moreover, L-NAME (5 mg/kg) blocked the enhancing effect of melatonin (10 mg/kg) on proconvulsant activity of morphine (60 mg/kg). Our results indicate that co-administration of melatonin enhances both anti- and proconvulsant effects of morphine via a mechanism that may involve the nitric oxidergic pathway.

A comparison of the circadian rhythms and the levels of melatonin in patients with diurnal and nocturnal complex partial seizures

The aim of the present work was to assess serum melatonin levels and melatonin circadian rhythm in patients with diurnal and nocturnal complex partial epilepsy. Daily rhythms of melatonin were studied in patients with diurnal complex partial epilepsy (n=10), patients with nocturnal complex partial epilepsy (n=10), and a control group (n=10). All patients were under carbamazepine treatment. Serum melatonin samples were taken at 1000, 2200, 0100, and 0500 hours. We found that melatonin circadian rhythm was normal in all patients when compared with controls. Melatonin levels were low in both patients with nocturnal and patients with diurnal complex partial epilepsy compared with the control group at 1000, 2200, 0100, and 0500 hours; a statistically significant decrease in melatonin levels was observed in the patients with epilepsy at 1000 hours only. These findings suggest that melatonin levels and circadian rhythm of melatonin do not differ between patients with nocturnal and patients with diurnal complex partial epilepsy. Further detailed research is necessary to determine the factors that govern the nocturnal or diurnal occurrence of complex partial seizures.

Involvement of nitric oxide pathway in the acute anticonvulsant effect of melatonin in mice

Melatonin, the major hormone produced by the pineal gland, is shown to have anticonvulsant effects. Nitric oxide (NO) is a known mediator in seizure susceptibility modulation. In the present study, the involvement of NO pathway in the anticonvulsant effect of melatonin in pentylenetetrazole (PTZ)-induced clonic seizures was investigated in mice. Acute intraperitoneal administration of melatonin (40 and 80 mg/kg) significantly increased the clonic seizure threshold induced by intravenous administration of PTZ. This effect was observed as soon as 1 min after injection and lasted for 30 min with a peak effect at 3 min after melatonin administration. Combination of per se non-effective doses of melatonin (10 and 20 mg/kg) and nitric oxide synthase (NOS) substrate L-arginine (30, 60 mg/kg) showed a significant anticonvulsant activity. This effect was reversed by NOS inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME, 30 mg/kg), implying an NO-dependent mechanism for melatonin effect. Pretreatment with L-NAME (30 mg/kg) and N(G)-nitro-L-arginine (L-NNA, 10 mg/kg) inhibited the anticonvulsant property of melatonin (40 and 80 mg/kg) and melatonin 40 mg/kg, respectively. Specific inducible NOS (iNOS) inhibitor aminoguanidine (100 and 300 mg/kg) did not affect the anticonvulsant effect of melatonin, excluding the role of iNOS in this phenomenon, while pretreatment of with 7-NI (50 mg/kg), a preferential neuronal NOS inhibitor, reversed this effect. The present data show an anticonvulsant effect for melatonin in i.v. PTZ seizure paradigm, which may be mediated via NO/L-arginine pathway by constitutively expressed NOS.

Sleep disturbances in children with epilepsy compared with their nearest-aged siblings

The aim of the study was to compare sleep patterns in children with epilepsy with those of their non-epileptic siblings and to determine which epilepsy-specific factors predict greater sleep disturbance. We conducted a case-control study of 55 children with epilepsy (mean age 10y, range 4 to 16y; 27 males, 28 females) and their nearest-aged non-epileptic sibling (mean age 10y, range 4 to 18y; 26 males, 29 females). Epilepsy was idiopathic generalized in eight children (15%), symptomatic generalized in seven (13%), and focal in 40 (73%); the mean duration was 5 years 8 months. Parents or caregivers completed the Sleep Behavior Questionnaire (SBQ) and Child Behavior Checklist (CBCL) for patients and controls, and the Quality of Life in Childhood Epilepsy (QOLCE) for patients. Patients had a higher (more adverse) Total Sleep score (p<0.001) and scored worse than controls on nearly all subscales of the SBQ. In patients, higher Total Sleep scores were correlated with higher scores on the Withdrawn, Somatic complaints, Social problems, and Attention subscales of the CBCL, and significantly lower Total Quality of Life Scores. Refractory epilepsy, mental retardation, and remote symptomatic etiology predicted greater sleep problems in those with epilepsy. We conclude that children with epilepsy in this current study had significantly greater sleep problems than their non-epileptic siblings.

Effects of pinealectomy and the treatment with melatonin on the temporal lobe epilepsy in rats

The aim of the present work was to analyze the effects of pinealectomy in the development of the epilepsy model induced by pilocarpine in adult male rats. Group I: Wistar male adult rats were submitted to pinealectomy, and 7 days after surgery, these animals received pilocarpine (350 mg/kg, i.p.) to induce three distinct behavioral phases: status epilepticus, seizure-free, and chronic phases. This late, as well as all control groups were continuously video-recorded for 60 days, to study behavior parameters. These animals were killed and the brain sections were processed for Nissl and neo-Timm. Group II: Another group, also submitted to pinealectomy, received several injections of melatonin (2.5 mg/kg): 20 min before, concomitantly with pilocarpine, 30 min, 1 h, and 2 h after pilocarpine administration. Some animals from group I and all from group II were sacrificed 48 h following status epilepticus onset to perform TUNEL assay. The latency for status epilepticus onset, status epilepticus length as well as mortality rate during status epilepticus were similar for pinealectomized and control groups. On the other hand, pinealectomized rats presented minor duration of the silent period, a higher number of spontaneous seizures during the chronic phase, increased number of TUNEL-positive cells (acute phase), increased neuronal loss, and marked supragranullar mossy fibers sprouting (chronic phase) in the hippocampal formation, when compared with control groups. Our data show that the pinealectomy facilitates the epileptogenic process that follows the long-lasting status epilepticus. This facilitation can be partially reverted by the simultaneous administration of melatonin.

Circadian and seasonal variation of first febrile seizures

Time of occurrence of 188 first febrile seizures (FS) was recorded, both by four 6-hour periods and by hourly intervals. The frequency of events was significantly ( P < .001) increased from 6 to 11.59 pm with a peak between 5 and 8 pm . A seasonal peak was observed in January.

Characterization of nocturnal ultradian rhythms of melatonin in children with growth hormone-dependent and independent growth delay

To assess the existence of a possible nocturnal ultradian rhythm of melatonin in children, we analyzed 28 pediatric patients (mean age, 9.08 +/- 2.2 yr) with GH-dependent and GH-independent growth delay. Plasma melatonin was measured by RIA in children sampled every 30 min between 2100-0900 h. Statistical analysis consisted of cluster analysis to examine the presence of peaks and troughs. The pattern of melatonin levels was related to the cause of growth delay, although the means of the nocturnal concentrations of melatonin were similar in all children. Interestingly, children with a GH deficit showed a nearly normal melatonin profile, whereas children with normal GH values but abnormal growth displayed atypical profiles of melatonin. The results also prove the existence of an ultradian rhythm of melatonin in most of the patients studied. The ultradian rhythm of melatonin in children was characterized by irregular interburst intervals, thus differing from the rhythm previously described in adults that had an almost constant pulse frequency. Moreover, the existence of low and high melatonin producers was revealed in the study, a feature unrelated to the cause of growth delay. The group of children with a GH deficit showed the lowest values of integrated melatonin production and of the area of peaks and troughs. These results prove that children exhibit an ultradian rhythm of melatonin like that in adults. Whereas it is not clear whether the episodic production of melatonin is required for its biological actions, the existence of irregular pulses may reflect endocrine influences at this age and/or the immaturity of the intrinsic pulse generator.

Influence of melatonin upon the protective action of conventional anti-epileptic drugs against maximal electroshock in mice

Melatonin (50 mg/kg; 60 min before the test) significantly raised the electroconvulsive threshold in mice. The protective action of melatonin (50 mg/kg) in the electroconvulsive threshold test was reversed by aminophylline, picrotoxin and bicuculline. Melatonin at the subconvulsive dose of 25 mg/kg potentiated the anticonvulsive activity of carbamazepine and phenobarbital (ED50 values were significantly decreased from 12.1 to 8.3 and from 18.9 to 11.8 mg/kg, respectively). No potentiation was observed in the case of valproate and diphenylhydantoin (their ED50s were changed from 253 to 249 and from 10.3 to 9.7 mg/kg, respectively). Melatonin did not influence the plasma or brain levels of anti-epileptics studied, so a pharmacokinetic interaction is not probable. Melatonin (25 mg/kg) alone and its combinations with carbamazepine or phenobarbital, providing a 50% protection against maximal electroshock, were devoid of significant motor adverse effects, but caused strong long-term memory deficit. Consequently, it does not seem to be a good candidate for the treatment of epilepsy.

Melatonin's role as an anticonvulsant and neuronal protector: experimental and clinical evidence

The pineal gland classically has been considered as a vestigial and mystic organ. In the last decades, and with the incorporation of new methodologic procedures, it could be proved that it also has physiologic actions that vary depending on the level of the phylogenetic scale. Its best-known secretion, melatonin, has been related to many different actions, such as sleep promotion, control of biologic rhythms, hormonal inhibition, and an inhibiting action on central nervous system regulation mechanisms. In animal experimentation, there are papers even accepting an anticonvulsant effect. In humans, evidence is reduced to few experiences. In addition to this clinical experience, there is other evidence that clearly relates melatonin to convulsive phenomena. This relationship must be mediated by the following mechanisms attributed to melatonin: altered brain GABAergic neurotransmission, its known interaction with benzodiazepinic brain receptors, through tryptophan metabolite activity (kynurenine, kynurenic acid), or even by its efficacy as a free-radical scavenger.

Utility of high doses of melatonin as adjunctive anticonvulsant therapy in a child with severe myoclonic epilepsy: two years' experience

Recent data indicate that melatonin inhibits brain glutamate receptors and nitric oxide production, thus suggesting that it may exert a neuroprotective and antiexcitotoxic effect. Melatonin has been seen to prevent seizures in several animal models and to decrease epileptic manifestations in humans. The lack of response to conventional anticonvulsants in an epileptic child led us to use melatonin in this case. A female child who began to have convulsive seizures at the age of 1.5 months and was diagnosed as having severe myoclonic epilepsy was unsuccessfully treated with different combinations of anticonvulsants, including valproic acid, phenobarbital, clonazepam, vigabatrin, lamotrigin, and clobazam. Melatonin was thus added to the treatment. Imaging studies (CT, SPECT, and MNR), EEG recordings, blood biochemical, and hematological analyses, including measures of the circadian rhythm of melatonin, were made. The child was initially treated with various anticonvulsants. Severe neurological and psychomotor deterioration combined with increased seizure activity showed a lack of response to the treatment. At the age of 29 mon the patient was in a pre-comatose stage at which time melatonin was added to treatment. After 1 month of melatonin plus phenobarbital therapy and for a year thereafter, the child's seizures were under control. On reducing the melatonin dose after this time, however, seizures resumed and the patient's condition was re-stabilized after restoring melatonin. Prior to our attempts to reduce melatonin, all analyses, including EEG recordings and SPECT, were normal. As far as the results of neurological examination are concerned, only mild hypotony without focalization remained. Changes in the therapeutic schedules during the second year of melatonin treatment, including the withdrawal of phenobarbital, did not result in the same degree of seizure control, although progressively the child became satisfactorily controlled. At the present moment the child continues to have mild hypotony and shows attention disorder and irritability. Melatonin has proven to be useful as adjunctive therapy in the clinical control of this case of severe infantile myoclonic epilepsy. The results suggest that melatonin may have a useful role in mechanisms of neuroprotection and also indicate its use in other cases of untreatable epilepsy. Further studies using more patients and placebo-treatment would be beneficial in understanding the potential use of melatonin as a co-therapy in some cases of seizures.

5-Methoxytryptophol and melatonin in children: differences due to age and sex

It seems clear that the pineal hormone, melatonin (N-acetyl-5-methoxytryptamine), is involved in the reproductive behavior of several animal species including humans. Moreover, several data also support a role for 5-methoxytryptophol (ML), another pineal hormone, in the control of sexual processes. To test the role of ML in human reproductive axis, 128 healthy children, 68 boys and 60 girls, were studied. Each of these groups was divided in three age subgroups of 6, 11, and 14 years. A single blood sample (0900 hours) was obtained from each subject to determine melatonin, ML, FSH, LH, estradiol (girls), and testoterone (boys) by RIA. Statistical analysis of the data included ANOVA-II (factor I: age, factor II: sex) and an analysis of covariance with age as covariate. A similar plasma melatonin concentration, with a significant decrease between 6 and 11 years, was found in boys and girls. Melatonin concentrations correlate well with initiation of the pubertal development in these children, although no sex differences were found. Concentrations of ML are approximately 50% of those of melatonin. In contrast to melatonin, ML levels show significant age and sex differences. Plasma ML concentration significantly increased in boys (P < 0.001) and decreased in girls (P < 0.001) after 8 years of age. These results support the hypothesis that, besides melatonin, other pineal compounds such as ML may be involved in the maturation process in humans. The pineal indole ML may also be used as a marker of the different chronobiology in the pubertal development in boys and girls.

Pineal response after pyridoxine test in children

To characterize the pineal response to pyridoxine, plasma melatonin was measured in one hundred and twenty children 3 hours after vitamin B6 administration. The children, aged between 1.5 and 8 years, were divided in four groups as follows: a) control day group, grouping 27 children sampled at 9:00 and at 12:00; b) control night group, grouping 29 children sampled at 21:00 and at 24:00; c) pyridoxine day group, grouping 30 children sampled at 9:00, then intravenously (i.v.) injected with 3 mg/kg of pyridoxine, and sampled at 12:00; and d) pyridoxine night group, grouping 34 children sampled at 21:00, i.v. injected with 3 mg/kg of pyridoxine, and sampled at 24:00. Melatonin concentration was measured by radioimmuno assay. The data obtained showed a significant increase in melatonin levels after pyridoxine administration in the pyridoxine night group (39.87 +/- 8.02 pg/ml basal vs 88.45 +/- 9.21 pg/ml after pyridoxine, p < 0.001). The other groups did not showed significant differences in melatonin concentrations. Statistical analysis shows that the administration of pyridoxine during the nocturnal hours represents a stimulating factor to increase the pineal production of melatonin in children.