Anticonvulsive effect of paeoniflorin on experimental febrile seizures in immature rats: possible application for febrile seizures in children

Febrile seizures (FS) is the most common convulsive disorder in children, but there have been no clinical and experimental studies of the possible treatment of FS with herbal medicines, which are widely used in Asian countries. Paeoniflorin (PF) is a major bioactive component of Radix Paeoniae alba, and PF-containing herbal medicines have been used for neuromuscular, neuropsychiatric, and neurodegenerative disorders. In this study, we analyzed the anticonvulsive effect of PF and Keishikashakuyaku-to (KS; a PF-containing herbal medicine) for hyperthermia-induced seizures in immature rats as a model of human FS. When immature (P5) male rats were administered PF or KS for 10 days, hyperthermia-induced seizures were significantly suppressed compared to control rats. In cultured hippocampal neurons, PF suppressed glutamate-induced elevation of intracellular Ca(2+) ([Ca(2+)](i)), glutamate receptor-mediated membrane depolarization, and glutamate-induced neuronal death. In addition, PF partially suppressed the elevation in [Ca(2+)](i) induced by activation of the metabotropic glutamate receptor 5 (mGluR5), but not that mediated by α-amino-3-hydroxy-5-methyl-4-isoxazolpropionic acid (AMPA) or N-methyl-D-aspartate (NMDA) receptors. However, PF did not affect production or release of γ-aminobutyric acid (GABA) in hippocampal neurons. These results suggest that PF or PF-containing herbal medicines exert anticonvulsive effects at least in part by preventing mGluR5-dependent [Ca(2+)](i) elevations. Thus, it could be a possible candidate for the treatment of FS in children.     

Anticonvulsive and free radical scavenging activities of vanillyl alcohol in ferric chloride-induced epileptic seizures in Sprague-Dawley rats

Vanillyl alcohol (VA) is a component of Gastrodia elata Bl. (GE), which is a traditional Chinese herb widely used to treat convulsive disorders or dizziness. This study examined the role of VA in the anticonvulsive properties of GE in a Sprague-Dawley rat model of epilepsy. The anticonvulsive and free radical scavenging activities of VA were examined after intracortical injection of ferric chloride (100 mM, 8 microl) to induce epileptic seizures. These seizures were verified by behavioral observations and electroencephalographic (EEG) and electromyographic (EMG) recordings. Ferric chloride injection resulted in increased lipid peroxide levels in the ipsilateral and contralateral cerebral cortex, and increased luminol-chemiluminescence (CL) and lucigenin-CL counts in the peripheral blood. Intraperitoneal injection (i.p.) of VA (200 mg/kg or 100 mg/kg) or phenytoin 10 mg/kg prior to ferric chloride administration significantly inhibited wet dog shakes (WDS) and lipid peroxide levels in the bilateral cerebral cortex. VA 200 mg/kg also significantly reduced luminol-CL and lucigenin-CL counts in the peripheral blood, but no significant effect was observed following administration of VA 100 mg/kg or phenytoin. These data indicate that VA has both anticonvulsive and suppressive effects on seizures and lipid peroxidation induced by ferric chloride in rats. Data from the present study also demonstrate that VA has free radical scavenging activities, which may be responsible for its anticonvulsive propertics. This finding is consistent with the results from previous studies that generation of superoxide radical evoked by injection of iron salt into rat brain plays a critical role in ferric chloride-induced seizures. In addition, the results of the present study suggest that the anticonvulsive effect of GE may be attributable, at least in part, to its VA component.     

Reversible large-scale deformations in the membranes of electrically-treated cells: electroinduced bleb formation

Morphological changes in electrically-treated cells have been investigated by light and scanning electron microscopy. The application of 100-microseconds rectangular pulses of 1.3 kV/cm electric field to different types of cells (FBT, MEF, RAT-1, L-cells) in the physiological medium leads to the formation and growth of spherical and hemispherical protuberances of the cell membrane. The formation of such electroinduced blebs is not associated with the cells' death and is reversible. The electroinduced blebs are mainly formed at those sites of the cell membrane which are subjected to the highest voltage during the electric pulses. Increasing the tonicity of the medium by introducing 20 mM of inulin prevents the bleb formation, indicating the osmotically-dependent nature of the processes involved. When electric pulses are applied to the cells pre-treated with cytochalasin B, the formation of electroinduced blebs occurs independently from cytochalasin-induced ones originally present on such cells. Speculations are presented concerning the nature of the membrane structural changes underlying the electroinduced blebbing and their possible role in some electrically-induced processes.     

Effect of insulin-induced epileptic seizures on neutral glycolipids of rabbit cerebral cortex

The neutral glycolipids of rabbit central cortex were analyzed during epileptic seizures produced by insulin or pentetrazol injection. The two agents gave similar results. A decrease of glycolipid content occurred in the cortex and in the neuronal fraction during seizures. The normal glycolipid level was restored during the recovery phase.     

Anticonvulsive effect of the cerebrospinal fluid of cats with epileptic status

We studied the properties of the cerebrospinal fluid obtained from the cats with a formed epileptic status. Samples of such fluid were injected into the rats, in which later on such epileptic status was modeled. The clearly expressed anticonvulsive efficacy of such cerebrospinal fluid is demonstrated; it was manifested in a decrease of the duration of seizure reactions and prevention of the development of generalized clonico-tonic attacks. It is concluded that this effect is not species-specific, and the possible nature of an anticonvulsive profile of the fluid is discussed.     

Naloxone and the kindling of seizures.

In view of evidence indicating that endogenous opiate-like peptides have epileptiform effects, we examined the effect of the opiate antagonist naloxone on the kindling of seizures produced by repeated electrical stimulation of the amygdala or the caudate nucleus in rats. Naloxone had no effect on the threshold for local after-discharge in the two areas and failed to retard the rate of kindling of clinical seizures. These results suggest that an interaction of opiate-like peptides with central opiate receptors does not play any critical role in the kindling of seizures.     

Calcium Imaging of Neuronal Activity in Drosophila Can Identify Anticonvulsive Compounds

Although there are now a number of antiepileptic drugs (AEDs) available, approximately one-third of epilepsy patients respond poorly to drug intervention. The reasons for this are complex, but are probably reflective of the increasing number of identified mutations that predispose individuals to this disease. Thus, there is a clear requirement for the development of novel treatments to address this unmet clinical need. The existence of gene mutations that mimic a seizure-like behaviour in the fruit fly, Drosophila melanogaster, offers the possibility to exploit the powerful genetics of this insect to identify novel cellular targets to facilitate design of more effective AEDs. In this study we use neuronal expression of GCaMP, a potent calcium reporter, to image neuronal activity using a non-invasive and rapid method. Expression in motoneurons in the isolated CNS of third instar larvae shows waves of calcium-activity that pass between segments of the ventral nerve cord. Time between calcium peaks, in the same neurons, between adjacent segments usually show a temporal separation of greater than 200 ms. Exposure to proconvulsants (picrotoxin or 4-aminopyridine) reduces separation to below 200 ms showing increased synchrony of activity across adjacent segments. Increased synchrony, characteristic of epilepsy, is similarly observed in genetic seizure mutants: bangsenseless¹ (bss¹) and paralytic^K1270T (para^K1270T). Exposure of bss¹ to clinically-used antiepileptic drugs (phenytoin or gabapentin) significantly reduces synchrony. In this study we use the measure of synchronicity to evaluate the effectiveness of known and novel anticonvulsive compounds (antipain, isethionate, etopiside rapamycin and dipyramidole) to reduce seizure-like CNS activity. We further show that such compounds also reduce the Drosophila voltage-gated persistent Na⁺ current (I_NaP) in an identified motoneuron (aCC). Our combined assays provide a rapid and reliable method to screen unknown compounds for potential to function as anticonvulsants.     

Photomyoclonic seizures in the baboon, Papio papio.

The inborn seizure response of Papio papio to intermittent light stimulation has been reviewed as a model of human epilepsy. The electrographic and clinical features have been described and useful methodology has been outlined. A diurnal cyclicity in seizure responsiveness has been described with greatest seizure severity at 8 AM in parallel with a rise in urinary output of cortisol. Hormonal influences on the seizure response have been described for ethinyl estradiol, thyroxin, and triiodothyronine. Evidence regarding neurotransmitter involvement has been reviewed. Data regarding use of the animal for anticonvulsant testing in single and chronic doses has been discussed. Particular advantages of the model for study of age-related drug effects and the assessment of the effects of chronically administered anticonvulsant agents on learning and memory have been described.     

Local anesthetic-induced toxicity may be modified by low doses of flumazenil.

The purpose of this study was to investigate the influence of flumazenil on local anesthetic-induced acute toxicity. For each of the three tested anesthetics (etidocaine, mepivacaine and lidocaine) 6 groups of mice were treated by a single dose of flumazenil (0.125, 0.25, 0.5, 1 and 2 mg/kg), or an equal volume of saline, 15 minutes before the injection of the anesthetic (etidocaine: 50 mg/kg, mepivacaine: 110 mg/kg and lidocaine: 115 mg/kg). The convulsant activity, the time of latency to convulse and the mortality rate were assessed in each group. The local anesthetic-induced mortality was not significantly modified by flumazenil. The convulsant activity of lidocaine and mepivacaine was significantly increased by flumazenil but not for etidocaine. Also, increasing doses of flumazenil decreased the time of latency to obtain lidocaine-induced convulsions. This effect was not obtained with etidocaine or mepivacaine.