Different types of epilepsy may be found in nearly 1 % of population. Many epileptic syndromes originate during infancy and childhood and there are some age-specific syndromes demonstrating the influence of the level of brain maturation on generation, spread, arrest and consequences of epileptic seizures. Therefore, the main topics of the laboratory are epileptic seizures and epilepsies induced at different levels of postnatal development. Methods used in the laboratory include electrophysiology (acute and long term EEG recording, video-EEG monitoring, evoked potentials, electrical stimulation of different brain structures, activity of individual neurons), behavior (spontaneous behavior in open field, learning and memory tests), tests of motor performance, biochemistry, classical histology, histochemistry and immunohistochemistry. In collaboration with other laboratories molecular biology techniques are used. In addition, there is research in the field of computational neuroscience

Resarch is focused on the following topics

Status epilepticus as a life-threatening situation is modeled in adult as well as in developing rats. Status is induced by pilocarpine in lithiumpretreated animals at the age of 12, 25 or 90 days. video-EEG monitoring demonstrated that treatment with benzodiazepines and/or paraldehyde did not block but only interrupted seizures in all age groups. Epileptic EEG activity (mostly without motor correlates) reappears after a few tens of minutes and continues for at least 24 h. In contrast to older rats the youngest group exhibit frequently nongeneralized EEG seizures. Status epilepticus in immature brain is manifested in a little different way than in mature brain but the amount of epileptic activity is large enough to lead to permanent changes of the nervous system. Low doses of pilocarpine induce nonconvulsive seizures lasting approximately 90 minutes. Behavioral and EEG symptomatology of these seizures correspond with human complex partial seizures, i.e. our model is related to human nonconvulsive status epilepticus. These seizures can be elicited in all three age groups tested.

Spontaneous recurrent seizures which appear as a consequence of motor status epilepticus after a latent (silent) period represent a model of epilepsy because seizures appear repeatedly for the rest of life of the animals. Using the pilocarpine model of convulsive status epilepticus pathologic EEG activity (isolated spikes) can be recorded in all rats without any relationship to the age when status epilepticus was elicited. In contrast, ictal activity and especially convulsive, i.e. motor seizures are age-dependent; they regularly appeared when the animals have been seized during adulthood or, less regularly, at the age of 25 days.

Consequences of epileptic seizures during development are studied also behaviorally and morphologically. Convulsive status epilepticus during early development resulted in compromised motor development of rats (tested by a battery of tests on motor performance) and the changes are age-dependent, they have different time course in animals seized at the age of 12 or 25 days. Spatial memory task (Morris water maze) examined two months after status cannot be mastered by rats seized during adulthood, animals undergoing convulsive status at the age of 25 days learn more slowly than their control littermates but the youngest group do not exhibit any changes in comparison to controls. Spontaneous behavior in open field is characterized by a marked hyperactivity of all groups of animals after status. Both older age groups exhibit serious widespread brain damage seen in Nissl-stained brain sections – not only in the limbic system but also in neocortex, some thalamic nuclei and other structures. No obvious neuronal necrosis is present in rats seized at the age of 12 days but if immunohistochemical techniques are used, marked changes can be demonstrated even in this age group (e.g.loss of parvalbumin and calbindin positivity in piriform cortex). The findings lead us to a conclusion that motor status epilepticus is deleterious also for immature brain but its consequences differ from those in older animals. Nonconvulsive status epilepticus induced in adult rats resulted in morphological changes in motor neocortical area, i.e. even these innocent-looking seizures lead to longlasting changes in the brain.

The role of endogenous excitatory amino acids in the pathogenesis of epileptic seizures is investigated in immature rats, using systemic and intracerebroventricular administration of homocysteic acid. In addition to behavioral and EEG description of seizures, energy metabolite changes are studied. The findings suggest that the immature rat brain has   a high ability to compensate for the increased energy demands associated with seizure activity, most likely due to increased glycolysis. Seizures could be attenuated or prevented by antagonists of both NMDA and nonNMDA receptors and by metabotropic glutamate receptor subtypes of selective agists and antagonists, as evaluated by suppression of behavioral manifestations of seizures and also from the protection of metabolite changes which normally accompany these seizures. A pronounced anticonvulsant effect could be achieved by combined treatment with subthreshold doses of NMDA and nonNMDA receptor antagonists. This finding may be of potential significance for treatment of epilepsies.

The role of GABAergic inhibition in epileptogenesis in developing brain is mainly focused on the GABA-B system. An antagonist of GABA-B receptors CGP 35348 is able to suppress rhythmic spike-and-wave activity at all developmental stages where this activity could be evoked. In contrast, baclofen increased the incidence of spike-and-wave episodes in an age-dependent manner (from the fourth postnatal week). The GABA-B receptors participate in postictal depression after cortical epileptic afterdischarges. Development of Gproteins and adenylyl cyclase activity is studied in collaboration with the Department of Membrane Receptor Biochemistry. Glutamate decarboxylase activity is studied biochemically (in collaboration with the Faculty of Pharmacy, Charles University) and immunohistochemically. These studies are directed to possible changes induced by severe seizure activity. Molecular biology of GABA-B receptors is studied in the Laboratory of Molecular Physiology, a joint laboratory with the 3rd Medical School. The main topic is represented by the structure-function relationship of the metabotropic glutamate receptors and the GABA-B receptors. These G-protein- coupled receptors have certain similarities with other heptahelical receptors, but also many differences. Mutagenesis studies together with functional tests of heterologously expressed mutated proteins allow us to map contact sites of G-proteins with the receptors. Heterodimerization of BR1 and BR2 subunits of the GABA-B receptor is studied using protein chemistry and immunochemitry with the aim to disclose possible interaction sites that take parts in the receptor formation.

Action of antiepileptic drugs against different seizure models is studied during development. Two common models are motor seizures elicited by pentamethylenetetrazol administration and epileptic afterdischarges induced by rhythmic electrical stimulation of the sensorimotor area of cerebral cortex. These models make it possible to evaluate three or four different phenomena with known mechanisms of generation. There are not only quantitative but also qualitative changes of antiepileptic drug action with maturation of the brain - e.g.mixed GABA-A and GABA-B agonist progabide and GABA uptake blockers (NNC 711 and tiagabine) exhibit different action against generalized motor seizures in rats during the first three postnatal weeks and in adult animals. Ontogenetic changes in the action of phenytoin were demonstrated also electrophysiologically by means of evoked potentials. These results have not only theoretical but also direct practical significance.

In addition, mathematical analysis and modeling is focused on the information transfer from the input to a neuron to its output. This concerns either the first-order sensory neurons which are in direct contact with an external environment or neurons of higher orders receiving their input as integrated activity in a neuronal network. The main attention is oriented towards the sensory systems, mainly the olfactory one, however, due to the application of theoretical approaches closely related to experimental data, the results are of general validity. Methodologically, this is the type of computational neuroscience research using biophysical, mathematical and numerical tools.

Publications