Evaluation of the Role of Chronic Daily Melatonin Administration and Pinealectomy on Penicillin-Induced Focal Epileptiform Activity and Spectral Analysis of ECoG in Rats: An In Vivo Electrophysiological Study

Effective Protection Against Status Epilepticus Caused by Lithium-Pilocarpine: Combination of Midazolam and Lacosamide

AIM

Status epilepticus causes the most severe condition related to epilepsy in terms of high mortality rate. Although status epilepticus treatment guidelines specify a treatment process based on three-stage monotherapy, effective control cannot yet be achieved in all cases. In the presented study, with electrophysiological and behavioral tests, it was aimed to investigate the effectiveness of the combination of midazolam (MDZ), one of the most commonly used benzodiazepines in the first-line treatment of status epilepticus, with the second-line antiepileptics levetiracetam (LEV), lacosamide (LCM), valproic acid (VPA), and fosphenytoin (fPHT).

METHODS

A status epilepticus model was created with lithium-pilocarpine (5 mEq/kg-320 mg/kg) in adult male Sprague-Dawley rats with implanted electroencephalography (EEG) electrodes. MDZ (9 mg/kg) alone or in dual combinations with antiepileptic drugs (200 mg/kg LEV, 50 mg/kg LCM, 300 mg/kg VPA, 100 mg/kg fPHT) was injected i.p. to the experiment groups with status epilepticus. After video-EEG recordings were taken from the rats during and after status, the effects of drug interactions on cognitive and motor behaviors were examined by applying behavioral tests (open field, Rotarod, radial arm maze, and passive avoidance).

RESULTS

Compared with the untreated status epilepticus group, it was determined that MDZ alone and the combination of four antiepileptic drugs administered with MDZ significantly reduced the mortality rate, spike frequency, and spike amplitude of epileptic seizures and suppressed epileptic seizures at certain levels (p < 0.01). Compared to MDZ monotherapy, it was determined that the mortality rate and spike frequency and amplitude decreased significantly in the MDZ + LCM group (p < 0.01), whereas on the other hand, mortality and spike frequency increased in the MDZ + LEV group (p < 0.01). No negative effects were observed in learning and memory in all treatment groups, but it was determined that the motor functions of the animals treated with MDZ + fPHT were impaired compared to both the control group without any treatment and the MDZ group (p < 0.01).

CONCLUSION

In the status epilepticus model induced by lithium-pilocarpine, the combination of MDZ + LCM was found to be the most effective polytherapy option in reducing seizures and mortality. Additionally, it was observed that LEV, LCM, and VPA administered together with MDZ did not negatively affect both cognitive and motor functions.

The interaction between circadian rhythm and epilepsy

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

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

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