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The aim of this study was to examine the response of phrenic and hypoglossal motor outputs to hyperoxia and 11% hypoxia during picrotoxin-induced seizures. Adult rats were anesthetized with a mixture of urethane with alpha-chloralose. The animals were bilaterally vagotomized, paralyzed, and artificially ventilated. Picrotoxin was administered intravenously in a cumulative dose until seizures occurred. The response to changes in oxygen tension was studied after the convulsive dose of picrotoxin and compared with the baseline level. The results show that the picrotoxin-induced seizures evoked a complex respiratory response that consisted of an augmentation of phrenic and hypoglossal nerve activities and irregular disturbances in phasic respiratory discharges. The excitation of the hypoglossal activity appeared earlier and showed a more irregular pattern than that of the phrenic activity. Hyperoxia elicited a similar decrease in neural respiratory outputs during the control and seizure conditions, suggesting the unaltered peripheral chemoreceptor mechanism. In the pre-seizure condition, hypoxia caused an initial excitation of the phrenic and hypoglossal outputs followed by some decline of the effect. During seizures, the striking effect of hypoxia was a decrease of the respiratory rate. A biphasic response to hypoxia was maintained in the hypoglossal activity due to stimulation of the hypoglossal amplitude. In contrast, in the phrenic activity the excitatory phase of hypoxia was absent and depression ensued. The mechanism underlying the facilitation of hypoxic respiratory depression during seizures is discussed.
Recent fi ndings in experimental models and in the clinical setting highlight the possibility that infl ammatory processes in the brain contribute to the etiopathogenesis of seizures and to the establishment of a chronic epileptic focus. Prototypical infl ammatory cytokines such as IL-1β and TNF-α are overexpressed in epileptogenic brain areas, prominently by glia and to a lesser extent by neurons and endothelial cells of the blood brain barrier. Cytokine receptors are also upregulated, and the related intracellular signalling is activated, highlighting both autocrine and paracrine actions of cytokines in diseased brain. Cytokines can profoundly affect neuronal network excitability, and the recent demonstration of molecular and functional interactions between cytokines and classical neurotransmitters, such as glutamate and GABA, provides one mechanism by which cytokines affect neuronal activity. These interactions may result in increased tissue excitability leading to seizures and cell loss. These fi ndings describe novel communications between glia and neurons which may contribute to pathological conditions (e.g. seizures, neurodegeneration) characterized by the activation of infl ammatory processes, thus highlighting potential new targets for therapeutic intervention.
Background. It is estimated that approximately 1% of people worldwide suffer from epilepsy. Currently available antiepileptic drugs (AEDs) are able to control epileptic seizures in about 70% of cases. In the remaining patients (30%), the application of two or three AEDs in combination is necessary for effective seizure management. The goal of this work was to characterize the interaction of three AEDs: lacosamide (LCM), carbamazepine (CBZ) and valproate (VPA) at the fixed-ratio of 1:1:1 in the mouse tonic-clonic seizure model. Material and methods. Male albino Swiss mice, after receiving a combination of LCM, CBZ and VPA, were challenged with electric current to evoke tonic hind limb extension (seizure activity). Protection of the mice from tonic-clonic seizures was assessed by isobolographic analysis to determine the type of interaction occurring between these drugs. Results. Type I isobolographic analysis revealed that the combination of LCM, CBZ and VPA produced infra-additive (antagonistic) interaction in the mouse tonic-clonic seizure model. Conclusions. Since the three-drug mixture of LCM, CBZ a nd VPA exerted an antagonistic interaction in the tonic-clonic seizure test in mice, we would caution physicians against treating epilepsy patients with this unfavorable combination.
The aim of the present paper is the assessment of the overall complexity of spontaneous and non-paroxysmal EEG signals obtained from three groups of human subjects, e.g., healthy, seizure and mania. Linear complexity measure suitable for multi-variate signals, along with nonlinear measures such as approximate entropy (ApEn) and Taken's estimator are considered. The degree of linear complexity is significantly reduced for the pathological groups compared with healthy group. The nonlinear measures of complexity are significantly decreased in the seizure group for most of the electrodes, whereas a distinct discrimination between the maniac and healthy groups based on these nonlinear measures is not evident.
 In this work was investigated the effect of pre-treatment with (PhSe)2 and (PhTe)2 on chemical seizure and 4-aminopyridine-induced lethality in mice. Additionally, lipid peroxidation levels of whole brain after treatment with 4-aminopyridine and effect of pre-treatment with (PhSe)2 and (PhTe)2 on these levels were investigated. Mice were pre-treated with (PhSe)2 or (PhTe)2 (50, 100, or 150 µmol/kg) 30 min before 4-aminopyridine (12 mg/kg) administration. The treatment with 4-aminopyridine caused a significant incidence of seizures (clonic, tonic) and death. Pre-treatment with (PhSe)2 and (PhTe)2 significantly increased the latency for clonic and tonic seizures, and prevented 4-aminopyridine-induced death. Significantly, the pre-treatment with (PhSe)2 or (PhTe)2 increased the latency for clonic seizures in a dose-dependent manner. Additionally, a significant increase was observed in the brain lipid peroxidation level after treatment with 4-aminopyridine, which was significantly inhibited by pre-treatment with 150 µmol/kg (PhSe)2 or (PhTe)2. These results demonstrate that (PhSe)2 and (PhTe)2 counteract the harmful effects of 4-aminopyridine. It is possible that this effect results from modulation of the redox state of N-methyl-d-aspartate receptors and/or of Ca2+ channel activity with subsequent alteration in neurotransmitter release. Importantly, this study provides evidence for anticonvulsant and antioxidant properties of (PhSe)2 and (PhTe)2, which indicates a neuroprotective activity of these compounds.
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