Antidepressants but not antipsychotics have antiepileptogenic effects with limited effects on comorbid depressive-like behaviour in the WAG/Rij rat model of absence epilepsy

Evaluating bexicaserin for the treatment of developmental epileptic encephalopathies

INTRODUCTION

Developmental epileptic encephalopathies (DEEs) pose significant challenges due to their refractory nature and limited treatment options. Despite advancements in genetic understanding, effective therapies targeting underlying pathophysiology are lacking. Serotoninergic dysfunction has been implicated in epilepsy, sparking interest in serotonin as a therapeutic target.

AREA COVERED

This article explores the potential of bexicaserin, a selective 5-HT2C receptor agonist, as an adjunctive antiseizure medication in DEEs. Bexicaserin is thought to modulate GABAergic neurotransmission, suppressing central hyperexcitability. Preclinical studies demonstrate its efficacy across various seizure models. Clinical trials, including the Pacific Study, reveal promising results in reducing motor seizures. However, challenges such as adverse effects and treatment discontinuation underscore the need for further investigation.

EXPERT OPINION

The efficacy of 5-HT2C serotoninergic agonists, validated in preclinical and clinical studies, highlights serotonin's role in DEEs. Bexicaserin offers new therapeutic possibilities, potentially synergizing with existing antiseizure medications. Polypharmacotherapy, targeting distinct pathways, may enhance therapeutic outcomes. Monitoring pharmacological interactions and addressing central nervous system comorbidities are crucial for optimizing treatment strategies. Further research is needed to elucidate bexicaserin's mechanisms and potential antiepileptogenic effects.

Ketamine and fluoxetine exert similar actions on prelimbic and infralimbic responsivity to lateral septal nucleus stimulation in Wistar rats

Ketamine is a dissociative anesthetic that has been proposed to be a useful alternative in cases of a poor response to other treatments in patients with depression. Remarkably, beneficial clinical actions of ketamine are detected once its psychotropic actions disappear. Therefore, clinical actions may occur independently of dose. Most current studies focus on actions of ketamine on neurotrophic factors, but few studies have investigated actions of ketamine on neural structures for which actions of antidepressants have been previously explored. Lateral septal nucleus (LSN) stimulation reduces neural activity in the prelimbic cortex (PL) and infralimbic cortex (IL) subregions of the medial prefrontal cortex (mPFC). Fluoxetine increases inhibitory responsivity of the LSN-IL connection. In the present study, actions of an anesthetic dose of ketamine were compared with a high dose of fluoxetine on behavior and neural responsivity 24 h after drug administration. Fluoxetine reduced immobility in the forced swim test without changing locomotor activity in the open field test. Ketamine strongly decreased locomotor activity and did not produce changes in immobility. In another set of Wistar rats that received similar drug treatment regimens, the results indicated that LSN stimulation in saline-treated animals produced a long-lasting inhibitory afterdischarge in these mPFC subregions. Actions of ketamine on the LSN-mPFC connection reproduced actions of fluoxetine, consisting of accentuated inhibition of the LSN action on the mPFC. These findings suggest that independent of different actions on neurotransmission, the common final pathway of antidepressants lies in their actions on forebrain structures that are related to emotional regulation.

Antidepressant and Anxiolytic Effects of L-Methionine in the WAG/Rij Rat Model of Depression Comorbid with Absence Epilepsy

Depression is a severe and widespread psychiatric disease that often accompanies epilepsy. Antidepressant treatment of depression comorbid with epilepsy is a major concern due to the risk of seizure aggravation. SAMe, a universal methyl donor for DNA methylation and the synthesis of brain monoamines, is known to have high antidepressant activity. This study aimed to find out whether L-methionine (L-MET), a precursor of SAMe, can have antidepressant and/or anxiolytic effects in the WAG/Rij rat model of depression comorbid with absence epilepsy. The results indicate that L-MET reduces the level of anxiety and depression in WAG/Rij rats and suppresses associated epileptic seizures, in contrast to conventional antidepressant imipramine, which aggravates absence seizures. The antidepressant effect of L-MET was comparable with that of the conventional antidepressants imipramine and fluoxetine. However, the antidepressant profile of L-MET was more similar to imipramine than to fluoxetine. Taken together, our findings suggest that L-MET could serve as a promising new antidepressant drug with anxiolytic properties for the treatment of depression comorbid with absence epilepsy. Increases in the level of monoamines and their metabolites-DA, DOPAC, HVA, NA, and MHPG-in several brain structures, is suggested to be a neurochemical mechanism of the beneficial phenotypic effect of L-MET.

Sigma-1 receptor and seizures

Over the last decade, sigma-1 receptor (Sig1R) has been recognized as a valid target for the treatment of seizure disorders and seizure-related comorbidities. Clinical trials with Sig1R ligands are underway testing therapies for the treatment of drug-resistant seizures, developmental and epileptic encephalopathies, and photosensitive epilepsy. However, the direct molecular mechanism by which Sig1R modulates seizures and the balance between excitatory and inhibitory pathways has not been fully elucidated. This review article aims to summarize existing knowledge of Sig1R and its involvement in seizures by focusing on the evidence obtained from Sig1R knockout animals and the anti-seizure effects of Sig1R ligands. In addition, this review article includes a discussion of the advantages and disadvantages of the use of existing compounds and describes the challenges and future perspectives on the use of Sig1R as a target for the treatment of seizure disorders.

Optimization of Therapy in Patients with Epilepsy and Psychiatric Comorbidities: Key Points

Psychiatric disorder comorbidity in patients with epilepsy (PWE) is very frequent with a mean percentage prevalence of up to 50% and even higher. Such a high frequency suggests that epilepsy and psychiatric disorders might share common pathological pathways. Various aspects contribute in making the matter very complex from a therapeutic point of view. Some antiseizure medications (ASMs), namely valproic acid, carbamazepine, and lamotrigine, have mood-stabilising effects and are routinely used for the treatment of bipolar disorder in patients who do not have epilepsy. Pregabalin and, to a lesser extent, gabapentin, exerts anxiolytic effects. However, several ASMs, in particular levetiracetam, topiramate, and perampanel, may contribute to psychiatric disorders, including depression, aggressive behaviour, and even psychosis. If these ASMs are prescribed, the patient should be monitored closely. A careful selection should be made also with psychotropic drugs. Although most of these can be safely used at therapeutic doses, bupropion, some tricyclic antidepressants, maprotiline, and clozapine may alter seizure threshold and facilitate epileptic seizures. Interactions between ASMs and psychotropic medication may make it difficult to predict individual response. Pharmacokinetic interactions can be assessed with drug monitoring and are consequently much better documented than pharmacodynamic interactions. Another aspect that needs a careful evaluation is patient adherence to treatment. Prevalence of non-adherence in PWE and psychiatric comorbidities is reported to reach values even higher than 70%. A careful evaluation of all these aspects contributes in optimizing therapy with a positive impact on seizure control, psychiatric wellbeing, and quality of life.

Antidepressant Drugs for Seizures and Epilepsy: Where do we Stand?

People with epilepsy (PWE) are more likely to develop depression and both these complex chronic diseases greatly affect health-related quality of life (QOL). This comorbidity contributes to the deterioration of the QOL further than increasing the severity of epilepsy worsening prognosis. Strong scientific evidence suggests the presence of shared pathogenic mechanisms. The correct identification and management of these factors are crucial in order to improve patients' QOL. This review article discusses recent original research on the most common pathogenic mechanisms of depression in PWE and highlights the effects of antidepressant drugs (ADs) against seizures in PWE and animal models of seizures and epilepsy. Newer ADs, such as selective serotonin reuptake inhibitors (SRRI) or serotonin-noradrenaline reuptake inhibitors (SNRI), particularly sertraline, citalopram, mirtazapine, reboxetine, paroxetine, fluoxetine, escitalopram, fluvoxamine, venlafaxine, duloxetine may lead to improvements in epilepsy severity whereas the use of older tricyclic antidepressant (TCAs) can increase the occurrence of seizures. Most of the data demonstrate the acute effects of ADs in animal models of epilepsy while there is a limited number of studies about the chronic antidepressant effects in epilepsy and epileptogenesis or on clinical efficacy. Much longer treatments are needed in order to validate the effectiveness of these new alternatives in the treatment and the development of epilepsy, while further clinical studies with appropriate protocols are warranted in order to understand the real potential contribution of these drugs in the management of PWE (besides their effects on mood).

N-acetylcysteine aggravates seizures while improving depressive-like and cognitive impairment comorbidities in the WAG/Rij rat model of absence epilepsy

N-acetylcysteine (NAC) is an antioxidant with some demonstrated efficacy in a range of neuropsychiatric disorders. NAC has shown anticonvulsant effects in animal models. NAC effects on absence seizures are still not uncovered, and considering its clinical use as a mucolytic in patients with lung diseases, people with epilepsy are also likely to be exposed to the drug. Therefore, we aimed to study the effects of NAC on absence seizures in the WAG/Rij rat model of absence epilepsy with neuropsychiatric comorbidities. The effects of NAC chronic treatment in WAG/Rij rats were evaluated on: absence seizures at 15 and 30 days by EEG recordings and animal behaviour at 30 days on neuropsychiatric comorbidities. Furthermore, the mechanism of action of NAC was evaluated by analysing brain expression levels of some possible key targets: the excitatory amino acid transporter 2, cystine-glutamate antiporter, metabotropic glutamate receptor 2, the mechanistic target of rapamycin and p70S6K as well as levels of total glutathione. Our results demonstrate that in WAG/Rij rats, NAC treatment significantly increased the number and duration of SWDs, aggravating absence epilepsy while ameliorating neuropsychiatric comorbidities. NAC treatment was linked to an increase in brain mGlu2 receptor expression with this being likely responsible for the observed absence seizure-promoting effects. In conclusion, while confirming the positive effects on animal behaviour induced by NAC also in epileptic animals, we report the aggravating effects of NAC on absence seizures which could have some serious consequences for epilepsy patients with the possible wider use of NAC in clinical therapeutics.

Exendin-4 increases absence-like seizures and anxiety-depression-like behaviors in WAG/Rij rats

AIM

Epilepsy is a neurological condition affecting millions of people worldwide. Glucagon-like peptide-1 (GLP-1) is a gut hormone, and its neuroprotective effect was investigated in previous studies. In this study, the effects of exendin-4, a GLP-1 receptor agonist, were studied in genetic absence epileptic Wistar Albino Glaxo/Rijswijk rats (WAG/Rij). WAG/Rij rat is a genetic model of the absence epilepsy and depression-like comorbidity.

METHOD

We examined the effects of exendin-4 (10, 50 and 100 µg/kg) on the absence seizures (Electrocorticography [ECoG] recordings), anxiety level (open-field test [OF]), and depression-like levels (forced swimming test [FST]) in the WAG/Rij rats. Basal ECoG recording was performed for all rats. Then, exendin-4 (10, 50 or 100 µg/kg) was administered intraperitoneally and ECoG recording was made for 180 min. After ECoG recording, forced swimming test and open-field test were applied.

RESULTS

Administration of 10, 50, or 100 µg/kg exendin-4 increased the duration and number of spike-wave discharges (SWDs) considerably without changing the amplitude. The 100 µg/kg dose of exendin-4 was the most effective in increasing the total duration of SWDs. Additionally, all exendin-4 doses increased anxiety level in OF and depression-like level in FST.

CONCLUSION

Our results showed that exendin-4 increased SWD incidence and anxiety- and depression-like behaviors in the WAG/Rij rats. Besides, it was also found that high doses caused the most proabsence effect.

The effect of dexketoprofen trometamol on WAG/Rij rats with absence epilepsy (dexketoprofen in absence epilepsy)

AIM

Epilepsy is one of the most common neurological diseases. Dexketoprofen (DEX) is a nonselective nonsteroidal anti-inflammatory drug that is used as an analgesic. The present study aimed to assess the efficiency of DEX on WAG/Rij rats by electrophysiologically and behaviorally.

MATERIAL AND METHODS

Twenty-eight male WAG/Rij rats were used. The effects of acute treatment with DEX (5, 25, and 50 mg/kg, i.p) on absence-like seizures, and related psychiatric comorbidity were assessed. The ECoG recording was taken for 180 min before and after drug injection. After drug injection and EcoG recording, anxiety-depression-like behavior was tested with the open field test for 5 min.

RESULTS

The 5 mg/kg DEX significantly reduced the number and duration of SWDs percentage (p < 0.05) between 120 and 180 min, but 25 and 50 mg/kg DEX significantly increased the number and duration of SWDs percentage between 0 and 30 min (p < 0.05), and after 30 min the increase stopped (p > 0.05). And also, the 5 mg/kg DEX decreased the number and duration of SWDs percentage (p < 0.05) for 180 min (p < 0.05), but 25 and 50 mg/kg DEX administration did not alter (p > 0.05). The 5, 25, and 50 mg/kg doses of DEX significantly increased the duration of grooming (p < 0.05) but did not change the number of squares crossed (p > 0.05).

CONCLUSION

Low dose DEX reduced absence-like seizures, but care should be taken when using high doses in absence epilepsy. Also, it may be beneficial for painful diseases accompanied by anxiety-depression.

Absence seizures and their relationship to depression and anxiety: Evidence for bidirectionality

Absence seizures (AS), presenting as short losses of consciousness with staring spells, are a common manifestation of childhood epilepsy that is associated with behavioral, emotional, and social impairments. It has also been suggested that patients with AS are more likely to suffer from mood disorders such as depression and anxiety. This systematic review and meta-analysis synthesizes human and animal models that investigated mood disorders and AS. Of the 1019 scientific publications identified, 35 articles met the inclusion criteria for this review. We found that patients with AS had greater odds of developing depression and anxiety when compared to controls (odds ratio = 4.93, 95% confidence interval = 2.91-8.35, p < .01). The included studies further suggest a strong correlation between AS and depression and anxiety in the form of a bidirectional relationship. The current literature emphasizes that these conditions likely share underlying mechanisms, such as genetic predisposition, neurophysiology, and anatomical pathways. Further research will clarify this relationship and ensure more effective treatment for AS and mood disorders.

Etanercept rescues cognitive deficits, depression-like symptoms, and spike-wave discharge incidence in WAG/Rij rat model of absence epilepsy

Pro-inflammatory cytokines have been shown to be associated with the development of seizures in the WAG/Rij rat model of absence epilepsy. Importantly, WAG/Rij rats also exhibit cognitive deficits and depression-like behaviors. It is possible that pro-inflammatory cytokines mediate these comorbid conditions of absence epilepsy given their well-established effects on cognition and affective responses. The current study investigated the potential therapeutic effect of etanercept (tumor necrosis factor inhibitor) on cognitive impairment, depression-like behavior, and spike-wave discharges (SWDs) typically observed in the WAG/Rij rats. Eight-month-old male WAG/Rij rats and Wistar controls were tested in Morris water maze (MWM), passive avoidance (PA), forced swimming, sucrose preference, and locomotor activity tests, and electroencephalogram (EEG) recordings were taken from a separate group of WAG/Rij rats after 8 weeks of etanercept or vehicle treatment. Consistent with earlier work, WAG/Rij rats exhibited cognitive deficits and depression-like behavior. From these, the cognitive deficits and despair-like behavior were rescued by etanercept administration, which also reduced the frequency of SWDs without affecting their duration. Our results support the hypothesis that pro-inflammatory cytokines mediate the absence seizures and comorbid symptoms of absence epilepsy.

5-HT/GABA interaction in epilepsy

Epilepsy is a neurological condition characterized by synchronous neuronal oscillations (seizures) in the electroencephalogram. Seizures are classified in focal or generalized (depending on the brain territory interested during seizures), and in convulsive and/or not convulsive (depending on the presence or not of involuntary movements). The current pharmacological treatments are mainly based on GABA modulation although different neurotransmitters are also involved in epilepsy, including serotonin. However despite much extensive progress in the understanding of epilepsy mechanisms, still, a percentage of people with epilepsy are pharmaco-resistant calling for the need for new therapeutic targets. Here we review preclinical and human evidence showing that serotonin modulates epilepsy that this likely happens via a major modulation/interaction with GABA.

Raloxifene potentiates the effect of fluoxetine against maximal electroshock induced seizures in mice

The evidence to guide clinicians regarding rationale polytherapy with current antiepileptic drugs (AEDs) is lacking, and current practice recommendations are largely empirical.  The excessive drug loading with combinatorial therapies of existing AEDs are associated with escalated neurotoxicity, and that emergence of pharmacoresistant seizures couldn't be averted. In pursuit of judicious selection of novel AEDs in combinatorial therapies with mechanism based evidences, standardized dose of raloxifene, fluoxetine, bromocriptine and their low dose combinations, were experimentally tested for their impact on maximal electroshock (MES) induced tonic hind limb extension (THLE) in mice. Hippocampal neuropeptide Y (NPY) levels, oxidative stress and histopathological studies were undertaken. The results suggest the potentiating effect of 4 mg/kg raloxifene on 14 mg/kg fluoxetine against MES induced THLE, as otherwise monotherapy with 4 mg/kg raloxifene was unable to produce an effect. The results also depicted better efficacy than carbamazepine (20 mg/kg), standard AED. Most profoundly, MES-induced significant (P < 0.001) reduction in hippocampal NPY levels, that were escalated insignificantly with the duo-drug combination, suggesting some other mechanism in mitigation of electroshock induced seizures. These results were later corroborated with assays to assess oxidative stress and neuronal damage. In conclusion, the results demonstrated the propitious therapeutic benefit of duo-drug low dose combination of drugs; raloxifene and fluoxetine, with diverse mode of actions fetching greater effectiveness in the management of generalized tonic clonic seizures (GTCS).

Trazodone increases seizures in a genetic WAG/Rij rat model of absence epilepsy while decreasing them in penicillin-evoked focal seizure model

AIM

Psychiatric disorders, especially depression and anxiety, are among the most disabling comorbidities in patients with epilepsy, and they are difficult to treat because many antidepressants cause proconvulsive effects. Thus, it is important to identify the seizure risks associated with antidepressants. Trazodone is one of the most frequently prescribed selective serotonin reuptake inhibitor (SSRI) antidepressant drugs for the treatment of depression and anxiety. The aim of the present study was to evaluate the effects of trazodone on epileptiform activity in a penicillin-evoked focal seizure model in Wistar rats and in a genetic absence epilepsy model in Wistar Albino Glaxo/Rijswijk strain (WAG/Rij) rats.

METHODS

Trazodone at 5-, 10-, and 30-mg/kg doses was injected intraperitoneally in Wistar rats 30 min after penicillin injection, and spike frequency and amplitude of penicillin-induced epileptiform activity were evaluated. In a separate experimental model, the same trazodone doses were injected in WAG/Rij rats to elucidate their effects on number, duration, and amplitude of spike-and-wave discharges (SWDs) and on depression-anxiety like behavior. In both experimental groups, after trazodone injections recordings were made for 3 h. Depression-anxiety like behaviors in WAG/Rij rats were examined using forced swim test and open-field test.

RESULTS

Trazodone at 10- and 30-mg/kg doses significantly reduced the frequency of penicillin-induced epileptiform activity without changing the amplitude. Trazodone at a 5-mg/kg dose had no effect on either frequency or amplitude of epileptiform activity. Trazodone at all doses significantly increased number and duration of SWDs without changing the amplitude. In addition, all doses of trazodone decreased the number of squares crossed and duration of grooming in open-field test, and reduced swimming time activity and increased immobility time in forced swim test.

CONCLUSION

Our results suggest that depending on the dose used, trazodone had an anticonvulsant effect or no effect on penicillin-evoked focal seizure model, but all trazodone doses resulted in proconvulsant and depression-anxiety like behavior in WAG/Rij rats, which represent a genetic absence model of epilepsy.

Metabolic and Cognitive Effects of Ranolazine in Type 2 Diabetes Mellitus: Data from an in vivo Model

Type 2 diabetes mellitus (T2DM) is a risk factor for cognitive impairment. Ranolazine, an anti-ischemic drug used in the treatment of angina pectoris, has been shown to possess hypoglycemic properties in pre-clinical and clinical studies. The aim of this study was to evaluate the effects of ranolazine on glucose metabolism and cognitive function in a T2DM model of Wistar rats. Diabetes was induced by a high fat diet (HFD) and streptozotocin (STZ). The control group received a normal caloric diet (NCD) and sodium citrate buffer. Metformin, an effective hypoglycemic drug, was employed as a positive control. Animals were divided into the following groups: HFD/STZ + Ranolazine, HFD/STZ + Metformin, HFD/STZ + Vehicle, NCD + Vehicle, NCD + Ranolazine, and NCD + Metformin. Rats received ranolazine (20 mg/kg), metformin (300 mg/kg), or water, for 8 weeks. At the end of the treatments, all animals underwent to an intraperitoneal glucose tolerance test (IPGTT) and behavioral tests, including passive avoidance, novel object recognition, forced swimming, and elevate plus maze tests. Interleukin-6 plasma levels in the six treatment groups were assessed by Elisa assay. Body mass composition was estimated by nuclear magnetic resonance (NMR). Glucose responsiveness significantly improved in the HFD/STZ + Ranolazine (p < 0.0001) and HFD/STZ + Metformin (p = 0.003) groups. There was a moderate effect on blood glucose levels in the NCD + Ranolazine and NCD + Metformin groups. Lean body mass was significantly increased in the HFD/STZ + Ranolazine and HFD/STZ + Metformin animals, compared to HFD/STZ + Vehicle animals. Ranolazine improved learning and long-term memory in HFD/STZ + Ranolazine compared to HFD/STZ + Vehicle (p < 0.001) and ameliorated the pro-inflammatory profile of diabetic mice. These results support the hypothesis of a protective effect of ranolazine against cognitive decline caused by T2DM.

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.

Antiepileptogenic effects of Ethosuximide and Levetiracetam in WAG/Rij rats are only temporary

BACKGROUND

WAG/Rij rats represent a validated genetic animal model of epileptogenesis, absence epilepsy and depressive-like comorbidity. Some treatments (e.g. ethosuximide), using specific protocols, prevent the development of spontaneous absence seizures. Accordingly, ethosuximide increases remission occurrence in children with childhood absence epilepsy in comparison to valproic acid. Considering that in this animal model, antiepileptogenic effects are, in some cases, not retained over time, we studied whether the antiepileptogenic effects of both ethosuximide and levetiracetam (which also possesses antiepileptogenic effects in this and other animal epilepsy models) would be retained 5 months after drug suspension.

METHODS

WAG/Rij rats of ˜1 month of age were treated long-term with one of the two drugs at a dose of ˜80 mg/kg/day for 17 consecutive weeks; 1 and 5 months after drug suspension, the development of absence seizures as well as depressive-like behaviour were assessed by EEG recordings and the forced swimming test (FST).

RESULTS

In agreement with a previous report, both drugs continued to show antiepileptogenic effects 1 month after their discontinuation. Furthermore, ethosuximide improved depressive-like behaviour, whereas in contrast, levetiracetam worsened this symptom. However, none of the drugs maintained their antiepileptogenic effects 5 months after suspension, and in addition, animal behaviour in the FST returned to control conditions.

CONCLUSION

Overall, these results demonstrate that the antiepileptogenic effects of both ethosuximide and levetiracetam on absence seizure development and associated depressive-like behaviour in this model are only temporary.

Effects of vitamin D and paricalcitol on epileptogenesis and behavioral properties of WAG/Rij rats with absence epilepsy

AIM

Vitamin D (Vit D) has been considered as a neurosteroid and has a pivotal role in neuroprotection including epilepsy. Vit D regulator acts via a Vit D receptor (VDR). WAG/Rij rats have a genetically epileptic model of absence epilepsy with comorbidity of depression. The aim of the present study was to investigate the effect of Vit D and paricalcitol (PRC) on WAG/Rij rats.

MATERIAL AND METHODS

Sixty-three male WAG/Rij rats and seven male Wistar rats were used. The effects of acute and chronic treatment with Vit D (5.000 and 60.000 IU/kg, i.p) and PRC (0.5, 5 and 10 μg/kg, i.p) on absence seizures, and related psychiatric comorbidity were investigated in WAG/Rij rats. Depression-like behavior was assayed by using the forced swimming test (FST) and; anxiety-like behavior by using the open field test (OFT).

RESULTS

Acute Vit D treatments (5.000 and 60.000 IU/kg) similarly reduced the number and duration of spike-wave discharges (SWDs) and showed anxiolytic-antidepressive effect whereas there were no significant changes in other measured parameters between the daily and the bolus dose of Vit D. Acute administration of PRC (0.5, 5 and 10 μg/kg) showed anti-convulsive and anxiolytic-antidepressive effect. The dose (0.5 μg/kg) of PRC was the most effective dose. Chronic treatment was more effective than acute therapy in all parameters.

CONCLUSION

The results of the present study demonstrate that Vit D and PRC have antiepileptic and anxiolytic-antidepressive effects on the absence epilepsy in WAG/Rij rats.

Cognitive impairment in the WAG/Rij rat absence model is secondary to absence seizures and depressive-like behavior

Neuropsychiatric comorbidities are common in patients with epilepsy, remaining still an urgent unmet clinical need. Therefore, the management of epileptic disorders should not only be restricted to the achievement of seizure-freedom but must also be able to counteract its related comorbidities. Experimental animal models of epilepsy represent a valid tool not only to study epilepsy but also its associated comorbidities. The WAG/Rij rat is a well-established genetically-based model of absence epilepsy with depressive-like comorbidity, in which learning and memory impairment was also recently reported. Aim of this study was to clarify whether this cognitive decline is secondary or not to absence seizures and/or depressive-like behavior. The behavioral performance of untreated and ethosuximide-treated (300 mg/kg/day; 17 days) WAG/Rij rats at 6 and 12 months of age were assessed in several tests: forced swimming test, objects recognition test, social recognition test, Morris water maze and passive avoidance. According to our results, it seems that cognitive impairment in this strain, similarly to depressive-like behavior, is secondary to the occurrence of absence seizures, which might be necessary for the expression of cognitive impairment. Furthermore, our results suggest an age-dependent impairment of cognitive performance in WAG/Rij rats, which could be linked to the age-dependent increase of spike wave discharges. Consistently, it is possible that absence seizures, depressive-like behavior and cognitive deficit may arise independently and separately in lifetime from the same underlying network disease, as previously suggested for the behavioral features associated with other epileptic syndromes.

Effects of Histone Deacetylase Inhibitors on the Development of Epilepsy and Psychiatric Comorbidity in WAG/Rij Rats

Epigenetic mechanisms, such as alterations in histone acetylation based on histone deacetylases (HDACs) activity, have been linked not only to normal brain function but also to several brain disorders including epilepsy and the epileptogenic process. In WAG/Rij rats, a genetic model of absence epilepsy, epileptogenesis and mild-depression comorbidity, we investigated the effects of two HDAC inhibitors (HDACi), namely sodium butyrate (NaB), valproic acid (VPA) and their co-administration, on the development of absence seizures and related psychiatric/neurologic comorbidities following two different experimental paradigms. Treatment effects have been evaluated by EEG recordings (EEG) and behavioural tests at different time points. Prolonged and daily VPA and NaB treatment, started before absence seizure onset (P30), significantly reduced the development of absence epilepsy showing antiepileptogenic effects. These effects were enhanced by NaB/VPA co-administration. Furthermore, early-chronic HDACi treatment improved depressive-like behaviour and cognitive performance 1 month after treatment withdrawal. WAG/Rij rats of 7 months of age showed reduced acetylated levels of histone H3 and H4, analysed by Western Blotting of homogenized brain, in comparison to WAG/Rij before seizure onset (P30). The brain histone acetylation increased significantly during treatment with NaB or VPA alone and more markedly during co-administration. We also observed decreased expression of both HDAC1 and 3 following HDACi treatment compared to control group. Our results suggest that histone modifications may have a crucial role in the development of epilepsy and early treatment with HDACi might be a possible strategy for preventing epileptogenesis also affecting behavioural comorbidities.

Microglial activation: an important process in the onset of epilepsy

This study aimed to investigate the effects of microglial activation on the onset of epilepsy. Microglias cultured in vitro were stimulated with different concentrations of coriaria lactone (CL), and the effects on cell cycle and apoptosis were examined using flow cytometry. Then microglia were stimulated with 5×10^-5 mol/L CL, and levels of cyclin D1 and interleukin-1β (IL-1β) mRNA were measured by fluorescence quantitative PCR; tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) in supernatant were detected by radioimmunoassay. Finally, microglia-conditioned medium (MCM) obtained after various durations of CL treatment was infused into rat lateral ventricle, and rat behavior was observed and cortical electroencephalograms (EEGs) were recorded. Immunofluorescence staining was used to measure glutamate content in the rat cerebral cortex and hippocampus. Compared with the cell cycle phase distribution in the control group, the percentage of CL-treated cultured microglia in G0/G1 phase was significantly lower, while the percentages of microglia in S phase and G2/M phases were significantly higher. CL increased the gene expression of cyclin D1 and the secretion of TNF-α and IL-1β. Epileptic seizures were induced in rats after intraventricular injection with MCM from CL-treated cells, with animals showing bilateral beard shaking and forelimb tremor. EEGs from these animals exhibited epileptiform waveforms (such as spike waves, sharp waves and spike-slow waves), and glutamate content in the cerebral cortex and hippocampus was significantly increased. CL may therefore activate microglia by promoting proliferation and upregulation of cell factor (e.g., cyclin D1, TNF-α and IL-1β) expression. We have shown that CL-treated MCM can induce the onset of epilepsy in rats in vivo, and its mechanism of action may involve the upregulation of glutamate expression. In summary, microglial activation is an important link in the pathogenesis of the onset of epilepsy.

Pharmacology of epileptogenesis and related comorbidities in the WAG/Rij rat model of genetic absence epilepsy

Animal studies currently represent the best source of information also in the field of epileptogenesis research. Many animal models have been proposed and studied so far both from the pathophysiological and pharmacological point of view. Furthermore, they are widely used for the identification of potentially clinically valuable biomarkers. The WAG/Rij rat model, similarly to other genetic animal strains, represents a suitable animal model of absence epileptogenesis accompanied by depressive-like and cognitive comorbidities. Generally, animal models of epileptogenesis are characterized by an identifiable initial insult (e.g. traumatic brain injury), a latent phase lasting up to the appearance of the first spontaneous seizure and a chronic phase characterized by recurrent spontaneous seizures. In most of genetic models: the initial insult should be defined as the mutation causing epilepsy, which is not clearly defined in the WAG/Rij rat model; the latent phase ends at the appearance of the first spontaneous seizure, which is about 2-3 months of age in WAG/Rij rats and thereafter the chronic phase. WAG/Rij rats also display depressive-like comorbidity around the age of 4 months, which is apparently linked to the development of absence seizures considering both its ontogeny and the fact that drugs affecting absence seizures development also block the development of depressive-like behavior. Finally, WAG/Rij rats also display cognitive impairment in some memory tasks, however, this has not been yet definitively linked to absence seizures development and may represent an epiphenomenon. This review is focused on the effects of pharmacological treatments against epileptogenesis and their effects on comorbidities.

Neonatal whisker trimming in WAG/Rij rat pups causes developmental delay, encourages maternal care and affects exploratory activity in adulthood

WAG/Rij rats are genetically predisposed to absence epilepsy. Maternal behavior in WAG/Rij female rats is known to differ from that in non-epileptic females. We hypothesize that (1) mother's behavior may be changed as response to changes in pup's conditions; (2) sensory deprivation at the neonatal age affect learning and behavior in adulthood. All whiskers in WAG/Rij rat pups were trimmed daily during PN1-PN8. Maternal behavior was examined during the same period. It was found that in the control group, WAG/Rij females often demonstrated abnormally long (>1 min) repetitive purposeless stereotypical actions that were roughly classified as compulsive-like behavior. Mothers of the trimmed pups showed less compulsive-like behavior and more intensively interacted with pups and built better nests. Rat pups in the trimmed group had lower body weight on PN7-PN19 as compared to the control. In the trimmed group, maturation of motor skills and early behavioral patterns (i.e. walking, grooming, vertical activity, motor functions of forelimbs) showed 1-2 days delay in comparison to the control. At the age of 2-2.5 months, the locomotor activity in the trimmed rats differed from the control, but the level of anxiety was the same (the open field and the elevated plus maze). At the age of 6 months, the trimmed and control rats showed no differences in conditioned avoidance learning test, therefore, neonatal whisker trimming did not influence fear-based learning abilities in adulthood. It is hypothesized that an enhanced maternal care is capable to modulate development of brain functions in sensory deprived progeny.

Fingolimod Exerts only Temporary Antiepileptogenic Effects but Longer-Lasting Positive Effects on Behavior in the WAG/Rij Rat Absence Epilepsy Model

One of the major challenges in the epilepsy field is identifying disease-modifying drugs in order to prevent or delay spontaneous recurrent seizure onset or to cure already established epilepsy. It has been recently reported that fingolimod, currently approved for the treatment of relapsing-remitting multiple sclerosis, has demonstrated antiepileptogenic effects in 2 different preclinical models of acquired epilepsy. However, to date, no data exist regarding the role of fingolimod against genetic epilepsy. Therefore, we have addressed this issue by studying the effects of fingolimod in Wistar Albino Glaxo/Rijswijk (WAG/Rij) rats, a well-established genetic model of absence epilepsy, epileptogenesis, and neuropsychiatric comorbidity. Our results have demonstrated that an early long-term treatment with fingolimod (1 mg/kg/day), started before absence seizure onset, has both antiepileptogenic and antidepressant-like effects in WAG/Rij rats. However, these effects were transitory, as 5 months after treatment discontinuation, both absence seizure and depressive like-behavior returned to control levels. Furthermore, a temporary reduction of mTOR signaling pathway activity, indicated by reduced phosphorylated mammalian target of rapamycin and phosphorylated p70S6k levels, and by increased phosphorylated Akt in WAG/Rij rats of 6 months of age accompanied the transitory antiepileptogenic effects of fingolimod. Surprisingly, fingolimod has demonstrated longer-lasting positive effects on cognitive decline in this strain. This effect was accompanied by an increased acetylation of lysine 8 of histone H4 (at both 6 and 10 months of age). In conclusion, our results support the antiepileptogenic effects of fingolimod. However, the antiepileptogenic effects were transitory. Moreover, fingolimod might also have a positive impact on animal behavior and particularly in protecting the development of memory decline.

Effects of Psychotropic Drugs on Seizure Threshold during Electroconvulsive Therapy

OBJECTIVE

To analyze the relationship between seizure threshold (ST) and psychotropic drugs in patients treated with ECT.

METHODS

We examined clinical data from 43 patients. ST was titrated at each treatment session. We examined associations between ST and psychotropic drugs using multivariate correlation analyses. Data are presented as initial ST, the difference in ST between the first and 10th sessions (ΔST_10th), and the mean difference in ST between the first and last sessions (mean ΔST_last).

RESULTS

Multivariate regression analyses showed associations between initial ST and the total chlorpromazine-equivalent dose of antipsychotics (β=0.363, p<0.05). The total fluoxetine-equivalent dose of antidepressants was associated with ΔST_10th (β=0.486, p<0.01) and mean ΔST_last (β=0.472, p<0.01).

CONCLUSION

Our study elucidated possible effects of psychotropic drugs on ST shifts. Larger doses of antipsychotics were associated with higher initial ST, whereas higher doses of antidepressants were associated with stronger shifts in ST.

Neurochemical evidence based suggested therapy for safe management of epileptogenesis

Most of the clinically available antiepileptic drugs have only antiseizure effects and are reported unable to prevent epileptogenesis. In the past decade, several drugs underwent clinical trials for management of epileptogenesis, but none of the drugs tested was found effective. One of the major lacunas is availability of appropriate preclinical approaches to delineate mechanisms of epileptogenesis. Thus, the present study attempts to suggest a neurochemistry based approach for safe management of epileptogenesis. The altered neurochemical milieu in amygdala, cortex and hippocampus areas of the mice brain in naïve, kindled and kindling resistant animals has been delineated. The endogenous natural antiepileptogenic neurochemical defense mechanism observed in kindling resistant animals may uncover neurochemical mechanisms of epileptogenesis and in turn suggest us novel interventions for safe management of epileptogenesis. The kindling epileptogenesis was carried out in two month old male Swiss albino mice by administering subconvulsive pentylenetetrazole (35mg/kg; i.p.) at an interval of 48±2h for 42days. 2h after the last pentylenetetrazole injection, the animals were subjected to behavioral evaluations. Four hours after behavioral evaluation, all animals were euthanized and discrete parts of brain (amygdala, cortex and hippocampus) were harvested for neurochemical analysis. Results revealed that 60% of animals responded to kindling as observed with decreased seizure threshold, while the rest were found resistant. The kindled animals were found to be associated with anxiety, depression and cognitive impairment; while in kindling resistant animals no such behavioral deficits were observed. The neurochemical analysis revealed that in kindled animals altered glutamate-GABA neurotransmission, and decreased taurine, glycine, d-serine, monoamine levels with elevated indoleamine 2,3-dioxygenase activity were observed, which may be convicted for progression of kindling epileptogenesis. However, in kindling resistant animals elevated GABA, taurine, tryptophan, serotonin, glycine, and d-serine levels with decreased indoleamine 2,3-dioxygenase activity were observed as natural endogenous antiepileptogenic mechanisms, which may be foreseen as safe pharmacological targets for management of epileptogenesis.

Genetic background contributes to the co-morbidity of anxiety and depression with audiogenic seizure propensity and responses to fluoxetine treatment

BACKGROUND

Anxiety and depression are the most frequent comorbidities of different types of convulsive and non-convulsive epilepsies. Increased anxiety and depression-like phenotype have been described in the genetic absence epilepsy models as well as in models of limbic epilepsy and acquired seizure models, suggesting a neurobiological connection. However, whether anxiety and/or depression are comorbid to audiogenic epilepsy remains unclear. The aim of this study was to investigate whether anxiety or depression-like behavior can be found in rat strains with different susceptibility to audiogenic seizures (AS) and whether chronic fluoxetine treatment affects this co-morbidity.

METHODS

Behavior in the elevated plus-maze and the forced swimming test was studied in four strains: Wistar rats non-susceptible to AS; Krushinsky-Molodkina (KM) strain, selectively bred for AS propensity from outbred Wistar rats; and a selection lines bred for maximal AS expression (strain "4") and for a lack of AS (strain "0") from KM×Wistar F2 hybrids. Effects of chronic antidepressant treatment on AS and behavior were also evaluated.

RESULTS

Anxiety and depression levels were higher in KM rats (with AS) compared with Wistar rats (without AS), indicating the comorbidity with AS. However, in strains "4" and "0" with contrasting AS expression, but with a genetic background close to KM rats, anxiety and depression were not as divergent as in KMs versus Wistars. Fluoxetine treatment exerted an antidepressant effect in all rat strains irrespective of its effect on AS.

CONCLUSIONS

Genetic background contributes substantively to the co-morbidity of anxiety and depression with AS propensity.

Cerebral small vessel disease predisposes to temporal lobe epilepsy in spontaneously hypertensive rats

The link between cerebral small vessel disease (CSVD) and epilepsy has been poorly investigated. Some reports suggest that CSVD may predispose to temporal lobe epilepsy (TLE). Aim of this study was to evaluate whether spontaneously hypertensive rats (SHRs), an established model of systemic hypertension and CSVD, have a propensity to develop TLE more than generalized seizures. To this aim, amygdala kindling, as a model of TLE, and pentylenetetrazole (PTZ)-induced kindling, as a model of generalized seizures, have been used to ascertain whether SHRs are more prone to TLE as compared to Wistar Kyoto control rats. While young SHRs (without CSVD) do not differ from their age-matched controls in both models, old SHRs (with CSVD) develop stage 5 seizures in the amygdala kindling model (TLE) faster than age-matched control rats without CSVD. At odds, no differences between old SHRs and age-matched controls was observed in the development of PTZ kindling. Enalapril pre-treatment prevented the development of CSVD and normalized kindling development to control levels in SHRs. No difference was observed in the response to pharmacological treatment with carbamazepine or losartan. Overall, our study suggests that uncontrolled hypertension leading to CSVD might represent a risk factor for TLE. Further experimental studies are needed to unravel other risk factors that, along with CSVD, may predispose to TLE.

Perampanel effects in the WAG/Rij rat model of epileptogenesis, absence epilepsy, and comorbid depressive-like behavior

OBJECTIVE

Perampanel (PER), a selective non-competitive α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-receptor antagonist, exhibits broad-spectrum anticonvulsant activity in several seizure models, but its potential disease-modifying effects have not been investigated. Because of the relevance of AMPA receptors in epileptogenesis and psychiatric comorbidities, we studied the effects of PER in the WAG/Rij rat model of epileptogenesis, absence epilepsy, and depressive-like comorbidity.

METHODS

We investigated the effects of acute, subchronic, and chronic treatment with PER (0.25-3 mg/kg) on absence seizures, their development, and related psychiatric/neurologic comorbidity in WAG/Rij rats. Depression-related behavior was studied by using the forced swimming and the sucrose preference test; anxiety-related behavior by using the open field and elevated plus maze test; and memory by using the passive avoidance test.

RESULTS

PER (3 mg/kg/day orally for 17 weeks starting from P30) significantly reduced the development of absence seizures at 6 months of age (1 month after treatment withdrawal), but this effect was not maintained when reassessed 4 months later. Attenuated absence seizure development was accompanied by reduced depressive-like behavior in the forced swimming test (FST), whereas no effects were observed on anxiety-related behavior and memory. Subchronic (1 and 3 mg/kg/day orally for 1 week) and acute PER (0.25-1 mg/kg, i.p.) dosing did not affect established absence seizures and behavior.

SIGNIFICANCE

These results suggest that AMPA receptors are involved in mechanisms of epileptogenesis in an established model of absence epilepsy, and that these mechanisms differ from those responsible for seizure generation and spread when epilepsy has become established.

The Anticonvulsant Activity of a Flavonoid-Rich Extract from Orange Juice Involves both NMDA and GABA-Benzodiazepine Receptor Complexes

The usage of dietary supplements and other natural products to treat neurological diseases has been growing over time, and accumulating evidence suggests that flavonoids possess anticonvulsant properties. The aim of this study was to examine the effects of a flavonoid-rich extract from orange juice (OJe) in some rodent models of epilepsy and to explore its possible mechanism of action. The genetically audiogenic seizures (AGS)-susceptible DBA/2 mouse, the pentylenetetrazole (PTZ)-induced seizures in ICR-CD1 mice and the WAG/Rij rat as a genetic model of absence epilepsy with comorbidity of depression were used. Our results demonstrate that OJe was able to exert anticonvulsant effects on AGS-sensible DBA/2 mice and to inhibit PTZ-induced tonic seizures, increasing their latency. Conversely, it did not have anti-absence effects on WAG/Rij rats. Our experimental findings suggest that the anti-convulsant effects of OJe are likely mediated by both an inhibition of NMDA receptors at the glycine-binding site and an agonistic activity on benzodiazepine-binding site at GABA_A receptors. This study provides evidences for the antiepileptic activity of OJe, and its results could be used as scientific basis for further researches aimed to develop novel complementary therapy for the treatment of epilepsy in a context of a multitarget pharmacological strategy.

Everolimus improves memory and learning while worsening depressive- and anxiety-like behavior in an animal model of depression

Everolimus (EVR) is an orally-administered rapamycin analog that selectively inhibits the mammalian target of rapamycin (mTOR) kinase (mainly mTORC1 and likely mTORC2) and the related signaling pathway. mTOR is a serine/threonine protein kinase regulating multiple important cellular functions; dysfunction of mTOR signaling has also been implicated in the pathophysiology of several neurological, neurodegenerative, developmental and cognitive disorders. EVR is widely used as an anti-neoplastic therapy and more recently in children with tuberous sclerosis complex (TSC). However, no clear correlation exists between EVR use and development of central side effects e.g. depression, anxiety or cognitive impairment. We studied the effects of a 3 weeks administration of EVR in mice chronically treated with betamethasone 21-phosphate disodium (BTM) as a model of depression and cognitive decline. EVR treatment had detrimental effects on depressive- and anxiety-like behavior while improving cognitive performance in both control (untreated) and BTM-treated mice. Such effects were accompanied by an increased hippocampal neurogenesis and synaptogenesis. Our results therefore might support the proposed pathological role of mTOR dysregulation in depressive disorders and confirm some previous data on the positive effects of mTOR inhibition in cognitive decline. We also show that EVR, possibly through mTOR inhibition, may be linked to the development of anxiety. The increased hippocampal neurogenesis by EVR might explain its ability to improve cognitive function or protect from cognitive decline. Our findings suggest some caution in the use of EVR, particularly in the developing brain; patients should be carefully monitored for their psychiatric/neurological profiles in any clinical situation where an mTOR inhibitor and in particular EVR is used e.g. cancer treatment, TSC or immunosuppression.

Role for serotonin2A (5-HT2A) and 2C (5-HT2C) receptors in experimental absence seizures

Absence seizures (ASs) are the hallmark of childhood/juvenile absence epilepsy. Monotherapy with first-line anti-absence drugs only controls ASs in 50% of patients, indicating the need for novel therapeutic targets. Since serotonin family-2 receptors (5-HT₂Rs) are known to modulate neuronal activity in the cortico-thalamo-cortical loop, the main network involved in AS generation, we investigated the effect of selective 5-HT_2AR and 5-HT_2CR ligands on ASs in the Genetic Absence Epilepsy Rats from Strasbourg (GAERS), a well established polygenic rat model of these non-convulsive seizures. GAERS rats were implanted with fronto-parietal EEG electrodes under general anesthesia, and their ASs were later recorded under freely moving conditions before and after intraperitoneal administration of various 5-HT_2AR and 5-HT_2CR ligands. The 5-HT_2A agonist TCB-2 dose-dependently decreased the total time spent in ASs, an effect that was blocked by the selective 5-HT_2A antagonist MDL11,939. Both MDL11,939 and another selective 5-HT_2A antagonist (M100,907) increased the length of individual seizures when injected alone. The 5-HT_2C agonists lorcaserin and CP-809,101 dose-dependently suppressed ASs, an effect blocked by the selective 5-HT_2C antagonist SB 242984. In summary, 5-HT_2ARs and 5-HT_2CRs negatively control the expression of experimental ASs, indicating that selective agonists at these 5-HT₂R subtypes might be potential novel anti-absence drugs.

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5-HT2AR activation decreases absence seizures in GAERS.

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5-HT2CR activation decreases absence seizures in GAERS.

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5-HT2AR blockade increases absence seizures in GAERS.

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5-HT2CR blockade does not affect absence seizures in GAERS.

Cannabidiol and epilepsy: Rationale and therapeutic potential

Despite the introduction of new antiepileptic drugs (AEDs), the quality of life and therapeutic response for patients with epilepsy remains still poor. Unfortunately, besides several advantages, these new AEDs have not satisfactorily reduced the number of refractory patients. Therefore, the need for different other therapeutic options to manage epilepsy is still a current issue. To this purpose, emphasis has been given to phytocannabinoids, which have been medicinally used since ancient time in the treatment of neurological disorders including epilepsy. In particular, the nonpsychoactive compound cannabidiol (CBD) has shown anticonvulsant properties, both in preclinical and clinical studies, with a yet not completely clarified mechanism of action. However, it should be made clear that most phytocannabinoids do not act on the endocannabinoid system as in the case of CBD. In in vivo preclinical studies, CBD has shown significant anticonvulsant effects mainly in acute animal models of seizures, whereas restricted data exist in chronic models of epilepsy as well as in animal models of epileptogenesis. Likewise, clinical evidence seems to indicate that CBD is able to manage epilepsy both in adults and children affected by refractory seizures, with a favourable side effect profile. However, to date, clinical trials are both qualitatively and numerically limited, thus yet inconsistent. Therefore, further preclinical and clinical studies are undoubtedly needed to better evaluate the potential therapeutic profile of CBD in epilepsy, although the actually available data is promising.