Cortical epileptic foci elicited by local application of bicuculline methiodide represent a model of interictal epileptic activity with a transition into ictal phases. We studied a role of GABA-B receptors in this model using GABA-B receptor antagonist CGP35348 in adult rats with implanted cortical electrodes and cannula. CGP35348 (100 or 200 mg/kg i.p.) did not affect interictal discharges but it augmented ictal activity. Latency to the first ictal episode was decreased by the lower dose of CGP35348, duration of episodes was increased by the higher dose. GABA-B receptor antagonist did not influence purely cortical epileptic phenomenon but it is proconvulsant in ictal activity generated with participation of subcortical structures., P. Mareš, K Bernášková, H. Kubová., and Obsahuje seznam literatury
The action of phenytoin was studied in acute experiments in rats with brainstem transection at the midcollicular level. Symmetrical epileptogenic foci were elicited in sensorimotor cortical areas of both hemispheres by local application of penicillin. Seven rats formed a control group, ten animals were pretreated with phenytoin (60 mg/kg i.p., 10 min before penicillin application). Synchronization of interictal discharges in control rats was delayed in comparison to animals with an intact brainstem; phenytoin did not influence this synchronization. Spontaneous transition of interictal into ictal activity was not abolished by phenytoin, i.e. in cerveau isolé preparations phenytoin lost this activity. The loss of anticonvulsant activity was not complete. Ictal episodes were modified; they started as very short ones and their duration progressively increased. Structures localized below the level of transection represent a site of at least one of the mechanisms of phenytoin anticonvulsant action.
Action of antiepileptic drugs in immature brain may differ from that in adult brain. The aim of our study was to study an anticonvulsant action of lamotrigine and phenytoin, i.e. two drugs active against partial seizures in adult experimental animals as well as human patients, in a model of simple partial seizures in immature rats. Epileptic foci were induced by local application of bicuculline methiodide on sensorimotor cortical area of 12-dayold rat pups. The animals were pretreated with lamotrigine (LTG, 10 or 20 mg/kg i.p.) or phenytoin (PHT, 15, 30 or 60 mg/kg i.p.). Control rats for LTG received saline, controls for PHT solvent composed of propyleneglycol, ethanol and water. Influence of either drug on interictal activity was negligible. High doses of both LTG and PHT suppressed the transition into ictal phases and shortened the duration of persisting seizures. The tricomponent solvent exhibited moderate activity against ictal activity if compared with saline controls. The two drugs exhibited similar action in our model, i.e. the suppression of secondary generalization from epileptic focus. This action is comparable to that described for human patients and adult experimental animals. In favor of lamotrigine speaks the absence of serious side effects., K. Bernášková, P. Mareš., and Obsahuje bibliografii a bibliografické odkazy