Potassium channels as prominent targets and tools for the treatment of epilepsy.

INTRODUCTION: K+ channels are of great interest to epilepsy research as mutations in their genes are found in humans with inherited epilepsy. At the level of cellular physiology, K+ channels control neuronal intrinsic excitability and are the main contributors to membrane repolarization of active neurons. Recently, a genetically modified voltage-dependent K+ channel has been patented as a remedy for epileptic seizures. AREAS COVERED: We review the role of potassium channels in excitability, clinical and experimental evidence for the association of potassium channelopathies with epilepsy, the targeting of K+ channels by drugs, and perspectives of gene therapy in epilepsy with the expression of extra K+ channels in the brain. EXPERT OPINION: Control over K+ conductance is of great potential benefit for the treatment of epilepsy. Nowadays, gene therapy affecting K+ channels is one of the most promising approaches to treat pharmacoresistant focal epilepsy.

Ca2+-activated KCa3.1 potassium channels contribute to the slow afterhyperpolarization in L5 neocortical pyramidal neurons.

Layer 5 neocortical pyramidal neurons are known to display slow Ca2+-dependent afterhyperpolarization (sAHP) after bursts of spikes, which is similar to the sAHP in CA1 hippocampal cells. However, the mechanisms of sAHP in the neocortex remain poorly understood. Here, we identified the Ca2+-gated potassium KCa3.1 channels as contributors to sAHP in ER81-positive neocortical pyramidal neurons. Moreover, our experiments strongly suggest that the relationship between sAHP and KCa3.1 channels in a feedback mechanism underlies the adaptation of the spiking frequency of layer 5 pyramidal neurons. We demonstrated the relationship between KCa3.1 channels and sAHP using several parallel methods: electrophysiology, pharmacology, immunohistochemistry, and photoactivatable probes. Our experiments demonstrated that ER81 immunofluorescence in layer 5 co-localized with KCa3.1 immunofluorescence in the soma. Targeted Ca2+ uncaging confirmed two major features of KCa3.1 channels: preferential somatodendritic localization and Ca2+-driven gating. In addition, both the sAHP and the slow Ca2+-induced hyperpolarizing current were sensitive to TRAM-34, a selective blocker of KCa3.1 channels.

[Physiological Aspects of the Application of Hodgkin-Huxley Model of Action Potential Initiation for Invertebrate and Vertebrate Neurons].

Recent studies have revealed.that in contrast to invertebrate systems, the initiation of action potentials in vertebrate neurons significantly differ from the relatively slow exponential dynamics predicted by Hodgkin-Huxley equations, but rather is characterized by a sharp onset with a kink. These data provided new insights into the link between action potential initiation and abilities of neurons and neuronal networks to encode. high frequency signals. Here, we review recent models describing sharp onset dynamics of action potential initiation, including an alternative model of cooperative activation of sodium channels, as well as the influence of the dynamics of action potential initiation on computational abili- ties of neuronal networks. The importance this topic is due to the fact that, despite the rapid development of neuronal modeling during last decades, the well established models are unable to capture experimentally observed details of the onset dynamics of action potentials in mammalian neurons and the abilities of neurons to reliably encode code high frequency signals Recent advances of experimental and theoretical analysis of generation of action potentials and neuronal encoding, presented in this review, are ofgreat importance for better understanding of neuronal processing and development of a more precise and realistic neuronal model.

[DISORDERS OF LUNG FUNCTION IN THE EARLY POSTOPERATIVE PERIOD IN PATIENTS OPERATED ON THE ASCENDING AORTA WITH THE EXPANSION OF INTERVENTION ON THE AORTIC ARCH].

Precapillary artery--arterial (bronchial artery--pulmonay artery) anastomoses, come into play in cases where the locking artery open and alveoli washed arterialized blood. Normally, these anastomoses are closed. Intrapulmonary shunts carry blood supply acinar hinder extraordinary circumstances (chronic pulmonary embolism, surgery, occurring in cardiopulmonary bypass, when the flaw of blood through the Iungs is suspended for the duration of cardiopulmonary bypass). Patients operated on the ascending aorta with the expansion of intervention on the nortic arch during the correction of pathology carry blood supply only the central nervous system. All other organs and systems at this time were protected by mild hypothermia. However, during circulatory arrest, required for correction of pathology acinar damage as a result of hypoxia, probably because there is no blood flow in the pulmonary artery and there is no blood flow in the bronchial arteries. Last, in the ordinary course of artificial circulation, capable due to arterio-arterial pulmonary anastomoses prevent hypoxic damage to acinar, not lead to persistent hypoxemia in the immediate postoperative period in these patients, as a result of violations of lung diffusion capacity.

[Compartmentalization of neral non-synaptic plasticity at subcellular level].

One of the most efficient ways of CNS response to the variety of external and internal stimuli is a selective increase of excitability of neurons, acquired, for instance, during learning process. It is now well established, that persistent non-synaptic plasticity that emerging after learning, as well as synaptic one may serve an a substrate for long-term memory. Though, it remains unknown how the non-synaptic plasticity contributes to the alteration of the states of neuronal networks, which the long-term memory depends directly on. The explanation of how the non-synaptic plasticity is translated into the modified states of the neuronal networks and modified behavior remains one of the most important challenges of the contemporary research in the field of learning and memory. Also, little is known about the specific neuronal compartments ofthe axon and dendretic tree of that subjected to plastic changes in the context of morphological features of individual neuron and the efficiency of its input and output synapses subjected to indirect modifications due to non-synaptic plasticity and the influence of non-synaptic plasticity on the efficiency of neuronal synapses.

[Advanced optical recording of neuronal activity with voltage-sensitive dyes].

Currently, the studies of electrical activity and plasticity of neuronal networks are impossible without employing of imaging techniques to visualize functional signals that allowing revealing electrical events in multiple neurons, as well as in their tiny dendrites and axons placed on their morphological picture. Imaging with voltage-sensitive dyes (VSD) is one of unique available methods that providing both high spatial resolution and ultrafast sampling (< 0.1 ms) in realtime with perfect S-to-N ratio. During the last decade a significant progress in VSD application has been achieved due to major method improvements and new probe synthesis especially in the field of research of initiation and propagation of action potentials. There was evidence of the method efficiency and usability while the method was added to the toolbox of modern neuroscience for research in hottest topics.

[Fast and aimed delivery of voltage-sensitive dyes to mammalian brain slices by biolistic techniques].

Fast voltage-sensitive dyes (VSD) are widely used in modern neuroscience for optical recording of electrical potentials at many levels, from single cell compartment to brain areas, containing populations of many neural cells. The more lipophilic a VSD, the better signal-to-noise ratio of the optical signal, but there are no effective ways to deliver a water-insoluble dye into the membrane of live cell. Here we report a new protocol based on rapid biolistic delivery of VSDs, which is optimal for further recordings of optical signals from live neurons of rat brain slices. This protocol allows us to stain locally (150 mkm) neural somata of brain structures with a Golgi-like pattern, and a VSD propagates even to distant neurites of stained cells very quickly. This technique also can be used for rapid local delivery of any lipophilic and water-insoluble substances into live cells, further optical recording of neural activity, and analysis of potential propagation in a nerve cell.

[Functional organization and structure of the serotonergic neuronal network of terrestrial snail].

The extension of knowledge how the brain works requires permanent improvement of methods of recording of neuronal activity and increase in the number of neurons recorded simultaneously to better understand the collective work of neuronal networks and assemblies. Conventional methods allow simultaneous intracellular recording up to 2-5 neurons and their membrane potentials, currents or monosynaptic connections or observation of spiking of neuronal groups with subsequent discrimination of individual spikes with loss of details of the dynamics of membrane potential. We recorded activity of a compact group of serotonergic neurons (up to 56 simultaneously) in the ganglion of a terrestrial mollusk using the method of optical recording of membrane potential that allowed to record individual action potentials in details with action potential parameters and to reveal morphology of the neurons rcorded. We demonstrated clear clustering in the group in relation with the dynamics of action potentials and phasic or tonic components in the neuronal responses to external electrophysiological and tactile stimuli. Also, we showed that identified neuron Pd2 could induce activation of a significant number of neurons in the group whereas neuron Pd4 did not induce any activation. However, its activation is delayed with regard to activation of the reacting group of neurons. Our data strongly support the concept of possible delegation of the integrative function by the network to a single neuron.

Olfactory experience modifies the effect of odour on feeding behaviour in a goal-related manner.

Natural food odours elicit different behavioural responses in snails. The tentacle carries an olfactory organ, and it either protracts toward a stimulating carrot odour or retraces in a startle-like fashion away from a cucumber odour. The tentacle retraction to cucumber was still present after the snails were fed cucumber during inter-trial periods. Also, snails without any food experience displayed a longer latency to the first bite of cucumber than of carrot and rejected cucumber more often. After tasting these foods, the latency to carrot was not affected while the latency to and number of rejections of cucumber decreased. These results suggest that initial repulsive features of food odour can be only partially compensated by olfactory learning and feeding experience. In the present study, we demonstrated that an invertebrate can be repulsed or attracted by the same natural odour at the same time and that these behavioural responses are likely aimed at achieving different physiologically relevant goals.

[The time course of changes in early postoperative echocardiographic parameters in patients after reparative operations on the left ventricle and coronary bypass surgery].

The echocardiographic functional features of the left ventricle after its geometrical reconstruction in combination with myocardial revascularization were studied in 31 patients. The most significant parameters were defined, by evaluating the course of an early postoperative period.

Regulation of tentacle length in snails by odor concentration.

The upper tentacle of the snail, bearing the olfactory organ, produces complex movements when the snail explores a new environment. Tentacle trajectories were reconstructed in the presence and absence of odors using two simultaneous video recordings. Reconstructions showed that in the absence of odor, snails constantly scanned the surrounding space with the extended tentacles. Presentation of an odor elicited rapid flexion, independent of the odor concentration, accompanied by concentration-dependent tentacle contractions. Activation of identified motoneuron MtC3 is known to elicit tentacle contraction. Recordings made in semi-intact preparations showed that the dynamics and duration of the spike activity of MtC3 produced in response to odors correlated with the degree of tentacle contraction in response to odors. These data suggest that the central motoneuron MtC3, which triggers tentacle contraction, is involved in controlling the margins of the scanning field. Slow contraction or extension of the tentacle, associated with the level of MtC3 activity, may operate to tune the snail's investigative behavior to the conditions of the sensory environment.

Persistent sodium current is a target for cAMP-induced neuronal plasticity in a state-setting modulatory interneuron.

We have identified a TTX-resistant low-threshold persistent inward sodium current in the cerebral giant cells (CGCs) of Lymnaea, an important state-setting modulatory cell type of molluscan feeding networks. This current has slow voltage-dependent activation and de-activation kinetics, ultra-slow inactivation kinetics and fast de-inactivation kinetics. It activates at approximately -90 mV, peaks at approximately -30 mV, reverses at approximately +35 mV and does not show full voltage-dependent inactivation even at positive voltage steps. Lithium-sodium replacement experiments indicate that the persistent sodium current makes a significant contribution to the CGC membrane potential. Injection of cyclic adenosine monophosphate (cAMP) into the CGC cell body produces a large increase in the persistent sodium current that lasts for several hours. cAMP injection also leads to increased bursting, a significant decrease in the resistance and a significant depolarization of the soma membrane, indicating that cAMP-dependent mechanisms induce prolonged neuronal plasticity in the CGCs. Our observations provide the first link between cAMP-mediated modulation of a TTX-resistant persistent sodium current and prolonged neuronal plasticity in an identified modulatory cell type that plays an important role in behavioral state setting.

[Regulation of the length of the snail tentacle by the concentration-dependent contraction]. / Reguliatsiia dliny shchupal'tsa ulitki v zavisimosti ot kontsentratsii zapakha.

The tentacle of terrestrial snail with olfactory organs on the tips display complex behavior when snail investigates the new environment. We reconstructed the trajectory of the tentacle in three dimensions from two simultaneous video recordings in freely moving snail without odor and after odor application. We found that without oder the snail displayed continuous environment scanning with elongated tentacles. Odor application elicited startle-like short-term flexions of the tentacle which were independent from odor concentration and concentration-dependent gradual tentacle contraction. Identified central motoneuron MtC3 is known to produce the most part of the central tentacle retraction to the noxious stimuli. In nose-brain preparation the MtC3 responded to odors in concentration-dependent manner similar by dynamics and duration to the concentration-dependent gradual tentacle contraction in intact snail. It suggests that the MtC3 provides the central control of the extent of the scanning area by limiting the tentacle length. The MtC3-related gradual contraction of the tentacle can be aimed to tune the olfactory behavior of the terrestrial snail to the particular odor environment.

Phase-dependent coordination of two motor programs in the buccal ganglion of a pteropod mollusk.

Rhythmic activity in two independent structures of the digestive apparatus of Clione limacina--the radula and the hooks--is coordinated by neural networks in the buccal ganglion during feeding behavior. Optical recording of neuron activity in the buccal ganglion, which allows simultaneous recording of large numbers of neurons, showed that the activity of all neurons producing volley discharges can be assigned to only two phases of a single rhythm. Instead of the four theoretically possible phases of rhythmic neural activity, all experiments yielded recordings of biphasic activity, even in conditions of electrical stimululation of the cerebrobuccal connectives, which triggers rhythmic movements of this apparatus in preparations. These data demonstrate the phase-dependent coordination of two independent rhythmic food-procuring movements in Clione.

Optical recording of responses to odor in olfactory structures of the nervous system in the terrestrial mollusk Helix.

Electrophysiological methods and optical methods based on the use of potential-sensitive dyes were used to record stable rhythmic oscillations of local potentials in the olfactory structure (procerebrum) of the pulmonate mollusk Helix: these oscillations were generally similar to those previously observed in slugs. Odor had the effect of transiently altering rhythmic oscillations to generate an individual pattern. This is the first study describing the recording of procerebrum potentials evoked by presentation of odor, with mapping of the areas of propagation of these potentials relative to the areas of propagation of rhythmic oscillations. The boundary of the propagation of the evoked potential was essentially similar to the projection of the neuropil, and rhythmic oscillations were recorded in the projection layer of procerebrum cell bodies. Evoked potential waves appeared in areas corresponding to the site at which the olfactory nerve enters the cerebral ganglion (of which the procerebrum forms a part) and were propagated in the procerebrum neuropil towards the cell body layer. Evoked potentials did not provoke out-of-phase waves of rhythmic oscillations.

[Phase-dependent coordination of two motor programs in the buccal ganglion of a pteropod mollusk]. / Fazozavisimaia koordinatsiia dvukh motornykh programm v bukkal'nom ganglii krylonogogo molliuska.

Rhythmic activities of two feeding structures of the pteropod mollusk Clione limacina, redula and hooks, controlled by the neural networks in the buccal ganglia must be coordinated in order to produce a meaningful feeding response. Optical recording from the buccal ganglia, which allows the simultaneous activities of numerous neurons to be traced, revealed that such coordination exists in a phase-dependent manner. Instead of recording four theoretically possible phases of neuronal rhythmic activity, we always recorded only two phases, even after the electrical stimulation of the cerebro-buccal connective, which triggers both radula and hook rhythmic movements in the preparation.

Optical recording of odor-evoked responses in the olfactory brain of the naïve and aversively trained terrestrial snails.

Regular spontaneous oscillations were recorded both electro- and optophysiologically using a voltage-sensitive absorption dye in the olfactory part of the brain (procerebral lobe of the cerebral ganglia) of the gastropod mollusk Helix lucorum. Odor application caused transient changes in procerebral oscillations, and an odor-evoked potential was recorded in the procerebrum (PC). The wave of evoked potential originated near the place of olfactory nerve entrance into the PC and propagated via the procerebral neuropile toward the cell body layer. The spread of the odor-evoked potential corresponded roughly to the neuropile area, whereas the spontaneous oscillations were recorded in the cell body layer of the PC and were not observed in the neuropile. Evoked potential did not produce additional events intercalated into the ongoing spontaneous oscillations. Changes in parameters of spontaneous oscillations to the repeated presentations of the same odor were variable. To estimate the role of spontaneous oscillations in odor encoding, we trained the snail to avoid cineole, using paired presentations of cineole and electric shock. Elaboration of conditioned aversion to cineole applications resulted in distinct pairing-specific changes in behavior of the snails and procerebral activity. Responses to odor (cineole) applications were not different in amplitude or frequency of spontaneous oscillations in control and trained snails, whereas ratio of amplitudes of the same oscillation wave in proximal and distal regions of the procerebrum was significantly different in control and aversively trained snails, reflecting changes in neural firing in certain areas of the olfactory lobe.