Successful Treatment of Epilepsy with Serotonin Reuptake Inhibitors: Proposed Mechanism

PET imaging identifies anti-inflammatory effects of fluoxetine and a correlation of glucose metabolism during epileptogenesis with chronic seizure frequency

The serotonergic system has shown to be altered during epileptogenesis and in chronic epilepsy, making selective serotonin reuptake inhibitors interesting candidates for antiepileptogenic therapy. In this study, we aimed to evaluate disease-modifying effects of fluoxetine during experimental epileptogenesis. Status epilepticus (SE) was induced by lithium-pilocarpine, and female rats were treated either with vehicle or fluoxetine over 15 days. Animals were subjected to 18F-FDG (7 days post-SE), 18F-GE180 (15 days post-SE) and 18F-flumazenil positron emission tomography (PET, 21 days post-SE). Uptake (18F-FDG), volume of distribution (18F-GE180) and binding potential (18F-flumazenil) were calculated. In addition, hyperexcitability testing and video-EEG monitoring were performed. Fluoxetine treatment did not alter brain glucose metabolism. 18F-GE180 PET indicated lower neuroinflammation in the hippocampus of treated animals (-22.6%, p = 0.042), but no differences were found in GABAA receptor density. Video-EEG monitoring did not reveal a treatment effect on seizure frequency. However, independently of the treatment, hippocampal FDG uptake 7 days after SE correlated with seizure frequency during the chronic phase (r = -0.58; p = 0.015). Fluoxetine treatment exerted anti-inflammatory effects in rats during epileptogenesis. However, this effect did not alter disease outcome. Importantly, FDG-PET in early epileptogenesis showed biomarker potential as higher glucose metabolism correlated to lower seizure frequency in the chronic phase.

Exploring the Anticonvulsant Activity of Aqueous Extracts of Ficus benjamina L. Figs in Experimentally Induced Convulsions

Background. Ficus benjamina L. is an evergreen tree, native to Southeast Asia, and often known as a weeping fig. Its latex and fruit extracts are used by indigenous cultures to cure skin conditions, inflammation, vomiting, leprosy, malaria, and nasal ailments. The aqueous extract of the figs of Ficus benjamina L. has various therapeutic values, including biological activities on the central nervous system. Materials and Methods. The extract of the dried figs of Ficus benjamina L. (FBE) was prepared by defatting with petroleum ether for 16 h followed by soxhelation with 70% methanol (1 : 10 w/v) for 24 h, and standardization of the extract was carried out using HPLC with 5-HT as a standard. Electroconvulsions were induced by the maximal electroshock model, and chemoconvulsions were induced by picrotoxin. Results. The HPLC chromatogram of the Ficus benjamina L. extract showed an absorption peak with a retention time of 1.797 min, similar to that observed with standard serotonin (5-HT) solution. In the maximal electroshock model, FBE significantly reduced the duration of the tonic hind limb extensor and extensor-to-flexor ratio (E/F ratio) in a dose-dependent manner. Moreover, in the picrotoxin-induced seizure model, FBE increased the seizure latency and decreased the duration of tonic-clonic convulsions dose-dependently. We confirmed the anticonvulsant activity of the FBE extract as it attenuated both maximal electroshock and picrotoxin-induced convulsions. Conclusion. The in vivo studies revealed that the Ficus extract was found to protect the animals in electroshock-induced and picrotoxin-induced convulsions.

Endogenous and exogenous serotonin, but not sumatriptan, ameliorate seizures and neuroinflammation in the pentylenetetrazole-induced seizure model in rats

ABSTRACT Background: Epilepsy has neuropsychiatric comorbidities such as depression, bipolar disorder, and anxiety. Drugs that target epilepsy may also be useful for its neuropsychiatric comorbidities. Objective: To investigate the effects of serotonergic modulation on pro-inflammatory cytokines and the seizures in pentylenetetrazole (PTZ)-induced seizure model in rats. Methods: Male Wistar rats were injected intraperitoneally with serotonin, selective serotonin reuptake inhibitor fluoxetine, 5-HT1B/D receptor agonist sumatriptan, or saline 30 min prior to PTZ treatment. Behavioral seizures were assessed by the Racine's scale. Concentrations of IL-1β, IL-6, and TNF-α in serum and brain tissue were determined by ELISA. Results: Serotonin and fluoxetine, but not sumatriptan, alleviated PTZ-induced seizures by prolonging onset times of myoclonic-jerk and generalized tonic-clonic seizures. The anti-seizure effect of fluoxetine was greater than that of serotonin. Likewise, serotonin and fluoxetine, but not sumatriptan, reduced PTZ-induced increases in the levels of IL-1β and IL-6 in both serum and brain tissue. None of the administered drugs including PTZ affected TNF-α concentrations. Conclusions: Our findings suggest that endogenous and exogenous serotonin exhibits anticonvulsant effects by suppressing the neuroinflammation. It seems that 5-HT1B/D receptors do not mediate anticonvulsant and anti-neuroinflammatory effects of serotonin.

Sudden unexpected death in epilepsy: Respiratory mechanisms

Epilepsy is one of the most common chronic neurologic diseases, with a prevalence of 1% in the US population. Many people with epilepsy live normal lives, but are at risk of sudden unexpected death in epilepsy (SUDEP). This mysterious comorbidity of epilepsy causes premature death in 17%-50% of those with epilepsy. Most SUDEP occurs after a generalized seizure, and patients are typically found in bed in the prone position. Until recently, it was thought that SUDEP was due to cardiovascular failure, but patients who died while being monitored in hospital epilepsy units revealed that most SUDEP is due to postictal central apnea. Some cases may occur when seizures invade the amygdala and activate projections to the brainstem. Evidence suggests that the pathophysiology is linked to defects in the serotonin system and central CO₂ chemoreception, and that there is considerable overlap with mechanisms thought to be involved in sudden infant death syndrome (SIDS). Future work is needed to identify biomarkers for patients at highest risk, improve ascertainment, develop methods to alert caregivers when SUDEP is imminent, and find effective approaches to prevent these fatal events.

A ketogenic diet protects DBA/1 and Scn1aR1407X/+ mice against seizure-induced respiratory arrest independent of ketosis

Patients with uncontrolled epilepsy have a high risk of sudden unexpected death in epilepsy (SUDEP). Seizure-induced respiratory arrest (S-IRA) is thought to be the determining cause of death in many cases of SUDEP. The goal of the present study was to use Scn1aR1407X/+ (Dravet Syndrome, DS) and DBA/1 mice to determine: (1) the effect of a ketogenic diet (KD) on S-IRA and (2) the relationship between serum ketones and the protective effect of a KD. Ketogenic diet treatment significantly decreased spontaneous seizure-induced mortality in DS mice compared to control (8% vs 39%, p = 0.0021). This protective effect was not abolished when ketosis was prevented by supplementing the KD with glucose (10% mortality, p = 0.0007). In DBA/1 mice, the latency to onset of S-IRA due to audiogenic seizures was delayed from 7.6 to 20.8 seconds by a KD on treatment day (TD) 7 compared to control (p < 0.0001), an effect that was reversed on TD14 when mice were crossed over to a control diet on TD7. β-Hydroxybutyrate (BHB) levels were significantly decreased in DBA/1 mice on a KD supplemented with glucose (p = 0.0038), but the protective effect was maintained. Our findings show that a KD decreases SUDEP in DS mice and increases the latency to audiogenic S-IRA in DBA/1 mice. In both mouse models, a KD was protective against S-IRA. This effect may be due in part to specific dietary components rather than generation of ketone bodies.

Interneuron Dysfunction in a New Mouse Model of SCN1A GEFS

Advances in genome sequencing have identified over 1300 mutations in the SCN1A sodium channel gene that result in genetic epilepsies. However, it still remains unclear how most individual mutations within SCN1A result in seizures. A previous study has shown that the K1270T (KT) mutation, linked to genetic epilepsy with febrile seizure plus (GEFS+) in humans, causes heat-induced seizure activity associated with a temperature-dependent decrease in GABAergic neuron excitability in a Drosophila knock-in model. To examine the behavioral and cellular effects of this mutation in mammals, we introduced the equivalent KT mutation into the mouse (Mus musculus) Scn1a (Scn1a^KT) gene using CRISPR/Cas9 and generated mutant lines in two widely used genetic backgrounds: C57BL/6NJ and 129X1/SvJ. In both backgrounds, mice homozygous for the KT mutation had spontaneous seizures and died by postnatal day (P)23. There was no difference in mortality of heterozygous KT mice compared with wild-type littermates up to six months old. Heterozygous mutants exhibited heat-induced seizures at ∼42°C, a temperature that did not induce seizures in wild-type littermates. In acute hippocampal slices at permissive temperatures, current-clamp recordings revealed a significantly depolarized shift in action potential threshold and reduced action potential amplitude in parvalbumin (PV)-expressing inhibitory CA1 interneurons in Scn1a^KT/+ mice. There was no change in the firing properties of excitatory CA1 pyramidal neurons. These results suggest that a constitutive decrease in inhibitory interneuron excitability contributes to the seizure phenotype in the mouse model.

Serotonergic therapy in epilepsy

PURPOSE OF REVIEW

The serotonergic system is implicated in multiple aspects of epilepsy, including seizure susceptibility, sudden unexpected death in epilepsy (SUDEP), and comorbid depression. Despite the complexity of serotonin's effects on various neuronal networks, ongoing research provides considerable insight into the role of serotonin in human epilepsy. This review explores the potential roles of serotonergic therapies to improve clinical outcomes in epilepsy.

RECENT FINDINGS

In recent decades, research has markedly increased our knowledge of the diverse effects of serotonin on brain function. Animal models of epilepsy have identified the influence of serotonin on seizure threshold in specific brain regions, serotoninergic augmentation's protective effects on terminal apnea and mortality in SUDEP, and mechanisms underlying behavioral improvement in some models of comorbid depression. Human clinical studies are largely consistent with animal data but the translation into definitive treatment decisions has moved less rapidly.

SUMMARY

Evidence for serotonergic therapy is promising for improvement in seizure control and prevention of SUDEP. For some epilepsies, such as Dravet syndrome, basic research on serotonin receptor agonists has translated into a positive clinical trial for fenfluramine. The cumulative results of safety and efficacy studies support the routine use of SSRIs for comorbid depression in epilepsy.

Serotonin and sudden unexpected death in epilepsy

Epilepsy is a highly prevalent disease characterized by recurrent, spontaneous seizures. Approximately one-third of epilepsy patients will not achieve seizure freedom with medical management and become refractory to conventional treatments. These patients are at greatest risk for sudden unexpected death in epilepsy (SUDEP). The exact etiology of SUDEP is unknown, but a combination of respiratory, cardiac, neuronal electrographic dysfunction, and arousal impairment is thought to underlie SUDEP. Serotonin (5-HT) is involved in regulation of breathing, sleep/wake states, arousal, and seizure modulation and has been implicated in the pathophysiology of SUDEP. This review explores the current state of understanding of the relationship between 5-HT, epilepsy, and respiratory and autonomic control processes relevant to SUDEP in epilepsy patients and in animal models.

A protocol for a randomised controlled, double-blind feasibility trial investigating fluoxetine treatment in improving memory and learning impairments in patients with mesial temporal lobe epilepsy: Fluoxetine, Learning and Memory in Epilepsy (FLAME trial)

BACKGROUND

People with temporal lobe epilepsy (TLE) report significant problems with learning and memory. There are no effective therapies for combatting these problems in people with TLE, resulting in an unmet therapeutic need. The lack of treatment is, in part, due to a poor understanding of the neurobiology underlying these memory deficits. We know that hippocampal neurogenesis, a process believed to be important in learning and memory formation, is permanently reduced in chronic TLE, and this may go some way to explain the learning and memory impairments seen in people with TLE.The common anti-depressant drug fluoxetine has been shown to stimulate neurogenesis both in the healthy brain and in neurological diseases where neurogenesis is impaired. In an animal model of TLE, administration of fluoxetine was found to restore neurogenesis and improve learning on a complex spatial navigational task. We now want to test this effect in humans by investigating whether administration of fluoxetine to people with TLE can improve learning and memory.

METHODS

This is a single-centre randomised controlled, double-blind feasibility trial. We plan to recruit 20 participants with a diagnosis of TLE and uni-lateral hippocampal sclerosis, confirmed by 3T MRI. Eligible participants will undergo baseline assessments of learning and memory prior to being randomised to either 20 mg/day fluoxetine or matching placebo for 60 days. Follow-up assessments will be conducted after 60 days of trial medication and then again at 60 days after cessation of trial medication. Feasibility will be assessed on measures of recruitment, retention and adherence against pre-determined criteria.

DISCUSSION

This trial is designed to determine the feasibility of conducting a double-blind randomised controlled trial of fluoxetine for the treatment of learning and memory impairments in people with TLE. Data collected in this trial will inform the design and utility of any future efficacy trial involving fluoxetine for the treatment of learning and memory in people with TLE.

TRIAL REGISTRATION

EudraCT 2014-005088-34, registered on May 18, 2015.

Serotonergic mechanisms in the 6-Hz psychomotor seizures in mice

Serotonin (5-hydroxytrytamine (5-HT)) plays an important role in experimental seizures. Recently, we reported the depletion of 5-HT by parachlorophynylalanine (PCPA) in whole brain to enhance 6-Hz psychomotor seizures in mice. In the present work, we investigated the effect of 5-HT depletion in cortex and hippocampus, brain regions relevant for epilepsy, on behavioral and ultra-structural changes following 6-Hz psychomotor seizures in mice. In addition, we studied the effect of sodium valproate (SVP) on behavioral, biochemical, and ultra-structural effects induced by 6 Hz. Behavioral changes induced by 6 Hz stimulation were characterized as the increased duration of Straub's tail, stun position, twitching of vibrissae, forelimb clonus, and increased rearing and grooming. PCPA administration further enhanced while SVP reduced these behaviors in mice. The 6-Hz psychomotor seizure induced ultra-structural changes in both cortex and hippocampus in mice treated with PCPA. Furthermore, PCPA administrations followed by 6Hz-induced seizures were accompanied by reduced hippocampal and cortical 5-HT. SVP attenuated the PCPA-induced ultra-structural changes and alterations of 5-HT content in the mouse brain. The study suggests the involvement of 5-HT in the 6 Hz psychomotor seizures and in the mechanisms of action of SVP against such seizures in mice.

Serotonin depletion increases seizure susceptibility and worsens neuropathological outcomes in kainate model of epilepsy

Serotonin is implicated in the regulation of seizures, but whether or not it can potentiate the effects of epileptogenic factors is not fully established. Using the kainic acid model of epilepsy in rats, we tested the effects of serotonin depletion on (1) susceptibility to acute seizures, (2) development of spontaneous recurrent seizures and (3) behavioral and neuroanatomical sequelae of kainic acid treatment. Serotonin was depleted by pretreating rats with p-chlorophenylalanine. In different groups, kainic acid was injected at 3 different doses: 6.5mg/kg, 9.0mg/kg or 12.5mg/kg. A single dose of 6.5mg/kg of kainic acid reliably induced status epilepticus in p-chlorophenylalanine-pretreated rats, but not in saline-pretreated rats. The neuroexcitatory effects of kainic acid in the p-chlorophenylalanine-pretreated rats, but not in saline-pretreated rats, were associated with the presence of tonic-clonic convulsions and high lethality. Compared to controls, a greater portion of serotonin-depleted rats showed spontaneous recurrent seizures after kainic acid injections. Loss of hippocampal neurons and spatial memory deficits associated with kainic acid treatment were exacerbated by prior depletion of serotonin. The present findings are of particular importance because they suggest that low serotonin activity may represent one of the major risk factors for epilepsy and, thus, offer potentially relevant targets for prevention of epileptogenesis.

Proconvulsant effects of antidepressants - What is the current evidence?

Antidepressant drugs may have proconvulsant effects. Psychiatric comorbidity in epilepsy is common. Prescribers might be reluctant to initiate treatment with antidepressants in fear of seizure aggravation. The purpose of this review was to focus upon the current evidence for proconvulsant effects of antidepressants and possible clinical implications. Most antidepressants are regarded as safe and may be used in patients with epilepsy, such as the newer serotonin and/or noradrenaline reuptake inhibitors. Four older drugs should, however, be avoided or used with caution; amoxapine, bupropion, clomipramine and maprotiline. Proconvulsant effects are concentration-related. Optimization of drug treatment includes considerations of pharmacokinetic variability to avoid high serum concentrations of the most proconvulsant antidepressants. The risk of seizures is regarded as small and should, therefore, not hamper the pharmacological treatment of depression in people with epilepsy.

Model systems for studying cellular mechanisms of SCN1A-related epilepsy

Mutations in SCN1A, the gene encoding voltage-gated sodium channel NaV1.1, cause a spectrum of epilepsy disorders that range from genetic epilepsy with febrile seizures plus to catastrophic disorders such as Dravet syndrome. To date, more than 1,250 mutations in SCN1A have been linked to epilepsy. Distinct effects of individual SCN1A mutations on neuronal function are likely to contribute to variation in disease severity and response to treatment in patients. Several model systems have been used to explore seizure genesis in SCN1A epilepsies. In this article we review what has been learned about cellular mechanisms and potential new therapies from these model systems, with a particular emphasis on the novel model system of knock in Drosophila and a look toward the future with expanded use of patient-specific induced pluripotent stem cell-derived neurons.

Retrospective multicenter evaluation of the "fly-catching syndrome" in 24 dogs: EEG, BAER, MRI, CSF findings and response to antiepileptic and antidepressant treatment

The fly-catching syndrome (FCS) is a rare canine condition of sudden, occasional, or constant episodes of biting the air. It may be accompanied by jumping, licking, and swallowing. The etiology of FCS is unknown and controversial. Various explanations for its occurrence have included epileptoid disorders such as visual cortex epileptiform disturbances and simple and complex partial seizures as well as compulsive disorders, hallucinatory behavior, and stereotypy. A retrospective multicenter analysis of 24 dogs with clinical symptoms of FCS is presented. Clinical signs at the time of presentation, the mean age at onset of the disease, the response to treatment, and the clinical outcome were recorded and analyzed in all patients. All dogs underwent clinical, neurological, and otoscopic examinations. Complete blood cell counts (CBCs) and serum chemistry panels were obtained from each dog. Diagnostic testing included MRI and EEG examinations in 21 cases, BAER in 19 cases, and CSF analysis in 20 cases. The EEG revealed spike activity in 8 (38%) of the 21 cases, 7 of which had activity in the occipital lobes. The brainstem auditory evoked response (BAER) revealed three cases of bilateral deafness. The MRI revealed six cases of Chiari malformation (CM), one case of syringohydromyelia (SM), and one case of a falx cerebri meningioma. The dogs were divided into groups according to their treatment protocol. Group A included dogs treated with phenobarbital (PB), and group B consisted of dogs treated with fluoxetine (FLX). Thirty-six percent of the dogs in group A responded to PB, while 100% of the dogs in group B responded to FLX. The results suggest that FCS is more responsive to FLX than PB. However, the etiology of this behavior remains unclear in most cases.

Some cross-talks between immune cells and epilepsy should not be forgotten

Recent studies have reported that immune cells were not always found in brain specimens from epileptic patients, then should we stop investigating the relationship between these cells and epilepsy? The answer is no! In addition to immunocyte infiltration in brain parenchyma, a flurry of papers have demonstrated that there were significant alterations in peripheral blood cells (PBCs) immediately after seizure onset, especially changes in some specific transporters of neurotransmitters expressed on the membrane of immunocyte. These transporters may regulate neuronal excitability in mature neurons. Besides, many researchers did find activated leukocytes adhered to the endothelium of blood brain barrier or infiltrated into the brain parenchyma in several types of epilepsy both in human and animal studies; moreover, it is worth noting that different immune cells play different roles in epilepsy development, which was indicated by in vitro and in vivo evidence. This review is going to summarize available evidence supporting changes in PBCs after seizures, and will also focus on some specific effects of immune cells on epilepsy development.

Knock-in model of Dravet syndrome reveals a constitutive and conditional reduction in sodium current

Hundreds of mutations in the SCN1A sodium channel gene confer a wide spectrum of epileptic disorders, requiring efficient model systems to study cellular mechanisms and identify potential therapeutic targets. We recently demonstrated that Drosophila knock-in flies carrying the K1270T SCN1A mutation known to cause a form of genetic epilepsy with febrile seizures plus (GEFS+) exhibit a heat-induced increase in sodium current activity and seizure phenotype. To determine whether different SCN1A mutations cause distinct phenotypes in Drosophila as they do in humans, this study focuses on a knock-in line carrying a mutation that causes a more severe seizure disorder termed Dravet syndrome (DS). Introduction of the DS SCN1A mutation (S1231R) into the Drosophila sodium channel gene para results in flies that exhibit spontaneous and heat-induced seizures with distinct characteristics and lower onset temperature than the GEFS+ flies. Electrophysiological studies of GABAergic interneurons in the brains of adult DS flies reveal, for the first time in an in vivo model system, that a missense DS mutation causes a constitutive and conditional reduction in sodium current activity and repetitive firing. In addition, feeding with the serotonin precursor 5-HTP suppresses heat-induced seizures in DS but not GEFS+ flies. The distinct alterations of sodium currents in DS and GEFS+ GABAergic interneurons demonstrate that both loss- and gain-of-function alterations in sodium currents are capable of causing reduced repetitive firing and seizure phenotypes. The mutation-specific effects of 5-HTP on heat-induced seizures suggest the serotonin pathway as a potential therapeutic target for DS.

Protective activity of α-lactoalbumin (ALAC), a whey protein rich in tryptophan, in rodent models of epileptogenesis

The aim of the present work was to evaluate the potential activity of α-lactoalbumin (ALAC), a whey protein rich in tryptophan (TRP), in two rodent models of epileptogenesis and we explored a possible mechanism of action. The effects of ALAC (oral administration) were tested in two standard epileptogenesis protocols, namely the pilocarpine post-status epilepticus model in mice and the WAG/Rij rat model of absence epileptogenesis. The mechanism of action was investigated by assessing the effects of ALAC in two seizure models (N-methyl-d-aspartate (NMDA) and pentylenetetrazol (PTZ) -induced seizures) including d-serine co-administration. ALAC showed protecting properties in both models of epileptogenesis, reducing spontaneous seizures development. In acute seizure models, ALAC possessed antiseizure properties at some of the doses tested (PTZ-seizures: >50% seizure-reduction between 250 and 375 mg/kg; NMDA-seizures: >90% reduction at 250 and 500 mg/kg). When a dose of d-serine ineffective per se was co-administered with ALAC, ALAC effects were significantly reversed in both models. ALAC is active in experimental models of seizure and epileptogenesis. Its effects are likely mediated by the inhibition of NMDA receptors at the glycine binding site, possibly secondarily to the in vivo enzymatic conversion of ALAC-generated tryptophan to kynurenic acid. However, other mechanisms of action contributing to ALAC effects cannot be excluded.

Preclinical antiepileptic actions of selective serotonin reuptake inhibitors--implications for clinical trial design

Selective serotonin reuptake inhibitors (SSRIs) can reduce seizure frequency in humans, but no large-scale clinical trials have been done to test the utility of SSRIs as potential antiepileptic drugs. This may be caused in part by a small number of reports on seizures triggered by SSRI treatment. The preclinical literature on SSRIs is somewhat conflicting, which is likely to contribute to the hesitance in accepting SSRIs as possible anticonvulsant drug therapy. A careful review of preclinical studies reveals that SSRIs appear to have region-specific and seizure subtype-specific effects, with models of chronic partial epilepsy being more likely to respond than models of acute generalized seizures. Moreover, this preclinical profile is similar to that of clinical antiepileptic drugs. These observations suggest that SSRIs are promising antiepileptic agents, and that clinical trials may benefit from defining patient groups according to the underlying pathology.

Temporal lobe epilepsy masquerading as psychosis--a case report and literature review

The psychoses of epilepsy are well recognized complications of seizure disorders, diagnosed easily from the history. However, in the absence of recognized seizures, the diagnosis can be challenging. We present a 27-year-old female, who suffered a treatment refractory psychosis for 6 years. She did not report, or display, any seizure activity, and extensive investigation was unremarkable. The onset of new symptoms prompted a repeat work-up which clinched the diagnosis of psychosis of epilepsy. Treatment with Lamotrigine and Amisulpiride achieved an excellent response, and she has remained symptom free for 7 months. We conclude with a brief literature review.

Depression in temporal lobe epilepsy: a review of prevalence, clinical features, and management considerations

Depression in temporal lobe epilepsy has been established as a frequent occurrence, and various possible mechanisms for this significant comorbidity have been posited. However, there is still little to guide a clinician in the recognition and management of depression in patients with temporal lobe epilepsy. This is in part due to the lack of consistent findings in earlier studies, which was likely partly due to variabilities in methodology, sampling, and diagnosis of both temporal lobe epilepsy and depression. However, in recent years, significant effort has been made to address these issues and provide a framework for diagnosis and management of depression in this population. The following is a review of the literature, with special emphasis on clinical phenomenology of depressive symptoms, described bidirectional risk between depression and temporal lobe epilepsy, and treatment strategies in the context of potential drug interactions with antiepileptic drugs.

Coagulation abnormalities in children undergoing epilepsy surgery

OBJECT

Surgery is increasingly used to treat children with refractory epilepsy. Before surgery, the authors routinely evaluated the coagulation profile to identify coagulation abnormalities not established by personal and family history, physical examination, and routine screening tests.

METHODS

Thirty-nine consecutive children undergoing testing prior to epilepsy surgery were prospectively evaluated. The authors evaluated a detailed hematological history and an elaborative hematological panel including complete blood count, hepatic panel, anticoagulant levels, coagulation profile (prothrombin time, partial thromboplastin time, international normalized ratio, fibrinogen, thrombin time, von Willebrand antigen, ristocetin cofactor, factor VIII, and individual factor assays when indicated) and platelet aggregation studies (in the presence of adenosine diphosphate, epinephrine, collagen, and ristocetin). Patient variables included tuberous sclerosis complex (TSC), age at epilepsy onset, age at surgery, seizure frequency, number and type of antiepileptic drugs, recent or present ketogenic diet, and use of selective serotonin reuptake inhibitors.

RESULTS

Ten children (25.6%) had either coagulation or platelet function abnormalities. Abnormal coagulation was identified in 5 children, and abnormal platelet function was discovered in 6. A diagnosis of TSC was associated with a platelet function abnormality (p = 0.012), whereas children without TSC had a higher rate of coagulopathy (p = 0.041). None of the other characteristics reached statistical significance. In 2 patients (5.1%) with TSC and platelet aggregation abnormalities, the authors noted normal standard screening laboratory studies and an uneventful detailed personal and family history. One of these 2 patients developed a significant intraoperative bleeding complication.

CONCLUSIONS

A preoperative screening with standard laboratory studies and detailed history may not be adequate to fully examine underlying coagulation abnormalities in children with refractory epilepsy. Platelet aggregation studies should be considered in patients with TSC.

Preclinical activity profile of α-lactoalbumin, a whey protein rich in tryptophan, in rodent models of seizures and epilepsy

PURPOSE

To evaluate the potential anticonvulsant activity of α-lactalbumin (ALAC), a whey protein rich in tryptophan (TRP) relative to other large neutral amino acids (LNAAs), in rodent models of seizures and epilepsy.

METHODS

The effects of ALAC administered per os were evaluated by standard protocols against audiogenic seizures in Genetic Epilepsy Prone Rats (GEPR-9 rats), maximal electroshock (MES)-induced seizures in rats, pilocarpine-induced seizures in mice, spontaneous chronic seizures in mice exposed to pilocarpine-induced status epilepticus (SE), and absence seizures in WAG/Rij rats. In some models, carbamazepine (CBZ) was included as an active control. Plasma TRP/LNAAs ratios were measured by GC-MS.

RESULTS

Single doses of ALAC up to 500 or 6000 mg/kg were devoid of anticonvulsant activity in all models tested. Conversely, 5- and 12-day treatment with ALAC (250-1000 mg/kg/day) in GEPR rats reduced dose-dependently seizure scores and prolonged latency to clonus onset, with full persistence of the effect for up to 12h. ALAC (125-500 mg/kg/day for 15 days) protected against seizures induced by 250 mg/kg pilocarpine, but was less effective against higher pilocarpine doses. Similarly to CBZ, ALAC (125-500 mg/kg/day for 15 days) was also effective against spontaneous seizures in the post-pilocarpine SE model. ALAC (up to 6000 mg/kg/day for 12 days) did not prevent MES-induced seizures, although it reduced the duration of tonic extension at doses between 250 and 1000 mg/kg/day. Absence seizures in WAG/Rij rats were not significantly affected by ALAC. Plasma TRP/LNAAS ratios increased 2- to 3-fold after dosing with ALAC (250 mg/kg/day) for 7 and 14 days, respectively.

CONCLUSIONS

ALAC exerts significant protective activity against seizures in animal models, the effect being especially prominent against audiogenic seizures in GEPR-9 rats, seizures induced by low-dose pilocarpine in mice, and spontaneous seizures in mice exposed to pilocarpine-induced SE. This action is likely to be mediated by increased availability of TRP in the brain, with a consequent increase in 5-HT mediated transmission.

Serotonin transporter gene variation and refractory mesial temporal epilepsy with hippocampal sclerosis

We performed a molecular epidemiology study in a population of 105 mesial temporal lobe epilepsy with hippocampal sclerosis (MTE-HS) patients in order to investigate the role of a polymorphism in the serotonin transporter gene (SLC6A4) in the prediction of antiepileptic drug (AED) treatment response. Homozygous carriers of the 12-repeat allele had an almost fourfold increase in risk for a MTE-HS not responding to medical treatment (OR 3.88; CI 95% 1.40-10.7; p=0.006) compared to carriers of the 10-repeat allele. Therefore, a polymorphism of SLC6A4 might be a genetic marker of pharmacoresistance in MTE-HS patients.

Depression after status epilepticus: behavioural and biochemical deficits and effects of fluoxetine

Depression represents one of the most common comorbidities in patients with epilepsy. However, the mechanisms of depression in epilepsy patients are poorly understood. Establishment of animal models of this comorbidity is critical for both understanding the mechanisms of the condition, and for preclinical development of effective therapies. The current study examined whether a commonly used animal model of temporal lobe epilepsy (TLE) is characterized by behavioural and biochemical alterations involved in depression. Male Wistar rats were subjected to LiCl and pilocarpine status epilepticus (SE). The development of chronic epileptic state was confirmed by the presence of spontaneous seizures and by enhanced brain excitability. Post-SE animals exhibited increase in immobility time under conditions of forced swim test (FST) which was indicative of despair-like state, and loss of taste preference in saccharin solution consumption test which pointed to the symptomatic equivalence of anhedonia. Biochemical studies revealed compromised serotonergic transmission in the raphe-hippocampal serotonergic pathway: decrease of serotonin (5-HT) concentration and turnover in the hippocampus, measured by high performance liquid chromatography, and decrease of 5-HT release from the hippocampus in response to raphe stimulation, measured by fast cyclic voltammetry. Administration of fluoxetine (FLX, 20 mg/kg/day for 10 days) to naive animals significantly shortened immobility time under conditions of FST, and inhibited 5-HT turnover in the hippocampus. In post-SE rats FLX treatment led to a further decrease of hippocampal 5-HT turnover; however, performance in FST was not improved. At the same time, FLX reversed SE-induced increase in brain excitability. In summary, our studies provide initial evidence that post-SE model of TLE might serve as a model of the comorbidity of epilepsy and depression. The finding that behavioural equivalents of depression were resistant to an antidepressant medication suggested that depression in epilepsy might have distinct underlying mechanisms beyond alterations in serotonergic pathways.

Epileptic seizures but not pseudoseizures are associated with decreased density of the serotonin transporter in blood platelet membranes

The density of the serotonin transporter in the plasma membranes of blood platelets was evaluated by labelled paroxetine binding in three different groups. These groups were: normal controls, epileptic patients having undergone a recent seizure (less than 4 days before) and patients who equally recently presented psychogenic non-epileptic seizures (pseudoseizures). Real seizures resulted in a significant decrease of membrane serotonin transporter density. In the instances of pseudoseizures, its membrane density was undistinguishable from that of normal controls. These data lend further support to the idea that down regulation of serotonin transporter may play a homeostatic role in the cessation of epileptic seizures.

Direct enhancement of hippocampal dopamine or serotonin levels as a pharmacodynamic measure of combined antidepressant-anticonvulsant action

The neurobiological relationships between epilepsy and depression are receiving increased experimental attention. A key role for limbic monoamines in depression has been established and we recently showed the importance of hippocampal monoamines in limbic seizure control. We here studied whether anticonvulsant compounds are antidepressant and can elevate hippocampal dopamine (DA) or serotonin (5-HT) levels determined by in vivo microdialysis in rats. We used assessment of seizure severity in the focal pilocarpine model, antidepressant-like activity within the rat forced swim and the mouse tail suspension tests, and locomotor activity in an open field as behavioural tests. We studied the tricyclic antidepressant imipramine, the selective 5-HT reuptake inhibitor citalopram and the selective DA reuptake blocker GBR-12909. These compounds with combined antidepressant-anticonvulsant properties all directly enhanced extracellular hippocampal DA or 5-HT levels. Since glutamate-mediated hyperexcitability in temporal lobe regions seems to be involved in disturbed emotional behaviour, we next investigated possible antidepressant effects and hippocampal DA or 5-HT modulations exerted by selective ionotropic and metabotropic glutamate receptor ligands with anticonvulsant properties. Combined anticonvulsant-antidepressant activities of the NMDA antagonist MK-801 and the mGluR group I antagonists (AIDA, MPEP) were also associated with locally elicited increases in hippocampal DA and/or 5-HT levels. This study highlights that the hippocampus is an important site of action of combined anticonvulsant-antidepressant and monoamine enhancing effects.

Potentiation of brain serotonin activity may inhibit seizures, especially in drug-resistant epilepsy

In spite of the large number of antiepileptic drugs (AEDs) actually available, the problem of drug-resistant epilepsy has not been solved. No AEDs are efficacious in patients with pharmacoresitant epilepsy, so new hypothesises about the mechanisms of pharmacoresistance are needed. In the last years the ideas on the role of brain serotonin in epilepsy have been turned upside down: increasing the available brain serotonin is thought now to have an antiepileptic effect. Antidepressant drugs like selective serotonin re-uptake inhibitors, i.e., fluoxetine, have proved to be useful in seizure control. Tryptophan (Trp), an essential amino acid, is the only brain precursor of serotonin, it competes with the other large neutral amino acids (LNAAs) for the carrier of blood-brain barrier (BBB). Our own data has shown a lowering of plasmatic LNAA levels in epileptic patients, on the basis of these results we could estimate a decrease of a 1/3 in the Trp brain intake rate in epileptics in respect to controls. Increasing plasmatic Trp levels increases brain serotonin synthesis. Trp and 5-hydroxytryptophan (5-HTP) were tested as an add on in epilepsy, but the clinical outcome was controversial. Free amino acids are not fully adsorbed by the gastro-intestinal system, furthermore LNAAs, and also 5-HTP is a LNAA, compete to cross the intestinal membrane for the same carrier, like for the BBB. The best way to increase the plasmatic Trp level is a protein rich in Trp and poor in the other LNAAs. Unfortunately Trp is a limited amino acid in proteins. We report the clinical results obtained by adding a whey protein to the antiepileptic therapy of drug-resistant epileptic patients: alpha-lactoalbumin, rich in Trp and poor in the other LNAAs.

Localization of the serotonergic terminal fields modulating seizures in the genetically epilepsy-prone rat

Serotonin (5-HT) has been shown to exert antiepileptic effects in a variety of generalized convulsive seizure models, particularly the genetically epilepsy-prone rat (GEPR). The present study was designed to identify the region/site(s) where 5-HT exerts anticonvulsant effects in the GEPR-9, a model in which sound-evoked generalized tonic-clonic seizures (GTCS) are highly sensitive to manipulations in 5-HT concentration. Because the 5-HT reuptake inhibitor, fluoxetine, was known to exert anticonvulsant effects in GEPR-9s via a 5-HT-dependent mechanism, we utilized selective regional 5-HT depletion in combination with systemic fluoxetine administration to find the site where a 5-HT deficit would prevent the anticonvulsant action of fluoxetine. Widespread destruction of serotonergic terminal fields or regionally specific terminal field destruction was achieved using intracerebroventricular and more target specific infusions of 5,7-dihydroxytryptamine. The capacity of fluoxetine to suppress seizures in GEPR-9s following a loss of 5-HT was then examined. The present findings show the anticonvulsant action of fluoxetine is markedly attenuated following the loss of midbrain 5-HT, particularly in the region of the superior colliculus, while forebrain and spinal cord 5-HT do not appear to play a role in the action of fluoxetine. The importance of the deep layers of the SC was confirmed by demonstrating that direct microinfusion of fluoxetine into the SC can suppress seizures in rats pretreated with the 5-HT(1A) receptor antagonist pindolol.

Physiogenomic association of statin-related myalgia to serotonin receptors

We employed physiogenomic analyses to investigate the relationship between myalgia and selected polymorphisms in serotonergic genes, based on their involvement with pain perception and transduction of nociceptive stimuli. We screened 195 hypercholesterolemic, statin-treated patients, all of whom received either atorvastatin, simvastatin, or pravastatin. Patients were classified as having no myalgia, probable myalgia, or definite myalgia, and assigned a myalgia score of 0, 0.5, or 1, respectively. Fourteen single nucleotide polymorphisms (SNPs) were selected from candidates within the 5-HT receptor gene families [5a-hydroxytryptamine receptor genes (HTR) 1D, 2A, 2C, 3A, 3B, 5A, 6, 7] and the serotonin transporter gene (SLC6A4). SNPs in the HTR3B and HTR7 genes, rs2276307 and rs1935349, respectively, were significantly associated with the myalgia score. Individual differences in pain perception and nociception related to specific serotonergic gene variants may affect the development of myalgia in statin-treated patients.