Epilepsy is a group of neurological disorders commonly associated with the neuronal malfunction leading to generation of seizures. Recent reports point to a possible contribution of astrocytes into this pathology. We used the lithium-pilocarpine model of status epilepticus (SE) in rats to monitor changes in astrocytes. Experiments were performed in acute hippocampal slices 2–4 weeks after SE induction. Nissl staining revealed significant neurodegeneration in the pyramidal cell layers of hippocampal CA1, CA3 areas, and the hilus, but not in the granular cell layer of the dentate gyrus. A significant increase in the density of astrocytes stained with an astrocyte-specific marker, sulforhodamine 101, was observed in CA1 stratum (str.) radiatum. Astrocytes in this area were also whole-cell loaded with a morphological tracer, Alexa Fluor 594, for two-photon excitation imaging. Sholl analyses showed no changes in the size of the astrocytic domain or in the number of primary astrocytic branches, but a significant reduction in the number of distal branches that are resolved with diffraction-limited light microscopy (and are thought to contain Ca2+ stores, such as mitochondria and endoplasmic reticulum). The atrophy of astrocytic branches correlated with the reduced size, but not overall frequency of Ca2+ events. The volume tissue fraction of nanoscopic (beyond the diffraction limit) astrocytic leaflets showed no difference between control and SE animals. The results of spatial entropy-complexity spectrum analysis were also consistent with changes in ratio of astrocytic branches vs. leaflets. In addition, we observed uncoupling of astrocytes through the gap-junctions, which was suggested as a mechanism for reduced K+ buffering. However, no significant difference in time-course of synaptically induced K+ currents in patch-clamped astrocytes argued against possible alterations in K+ clearance by astrocytes. The magnitude of long-term-potentiation (LTP) was reduced after SE. Exogenous D-serine, a co-agonist of NMDA receptors, has rescued the initial phase of LTP. This suggests that the reduced Ca2+-dependent release of D-serine by astrocytes impairs initiation of synaptic plasticity. However, it does not explain the failure of LTP maintenance which may be responsible for cognitive decline associated with epilepsy.

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We propose a memristive interface consisting of two FitzHugh–Nagumo electronic neurons connected via a metal–oxide (Au/Zr/ZrO2(Y)/TiN/Ti) memristive synaptic device. We create a hardware–software complex based on a commercial data acquisition system, which records a signal generated by a presynaptic electronic neuron and transmits it to a postsynaptic neuron through the memristive device. We demonstrate, numerically and experimentally, complex dynamics, including chaos and different types of neural synchronization. The main advantages of our system over similar devices are its simplicity and real-time performance. A change in the amplitude of the presynaptic neurogenerator leads to the potentiation of the memristive device due to the self-tuning of its parameters. This provides an adaptive modulation of the postsynaptic neuron output. The developed memristive interface, due to its stochastic nature, simulates a real synaptic connection, which is very promising for neuroprosthetic applications.

We propose an optoelectronic system for stimulation of living neurons. The system consists of an electronic circuit based on the FitzHugh–Nagumo model, an optical fiber, and a photoelectrical converter. We used this system for electrical stimulation of hippocampal living neurons in acute hippocampal brain slices (350-μm thick) obtained from a 20–28 days old C57BL/6 mouse or a Wistar rat. The main advantage of our system over other similar stimulators is that it contains an optical fiber for signal transmission instead of metallic wires. The fiber is placed between the electronic circuit and stimulated neurons and provides galvanic isolation from external electrical and magnetic fields. The use of the optical fiber allows avoiding electromagnetic noise and current flows which could affect metallic wires. Furthermore, it gives us the possibility to simulate “synaptic plasticity” by adaptive signal transfer through optical fiber. The proposed optoelectronic system (hybrid neural circuit) provides a very high efficiency in stimulating hippocampus neurons and can be used for restoring brain activity in particular regions or replacing brain parts (neuroprosthetics) damaged due to a trauma or neurodegenerative diseases.

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The dynamics of memristive device in response to neuron-like signals and coupling electronic neurons via memristive device has been investigated theoretically and experimentally. The simplest experimental system consists of electronic circuit based on the FitzHugh-Nagumo model and metaloxide memristive device. The hardware-software complex based on commercial data acquisition system is implemented for the imitation of signal from presynaptic neuron`s membrane and synaptic signal transmission between neurons. The main advantage of our system is that it uses real time dynamics of memristive device. Electrical response of memristive device shows its behavioral flexibility that allows presenting a memristive device as an active synapse. This means an internal adjustment of the parameters of memristive device that leads to modulation of neuron-like signals.Physics-based dynamical model of memristor is developed in MATLAB for numerical simulation of such a memristive interface to describe and predict experimentally observed regularities of synchronization of neuron-like oscillators. FitzHugh-Nagumo circuits time series with a linear or stepwise increase in the signal amplitude are used to study the memristor response and coupling of neuron-like oscillators taking into account the stochasticity of memristor model to compare the numerical and experimental data. The observed forced synchronization modes characterize the dynamic complexity of the memristive device, which requires further description using high-order dynamical models. The developed memristive interface will provide high efficiency in the imitation of the synaptic connection due to its stochastic nature and can be used to increase the flexibility of neuronal connections for neuroprosthetic challenges.

The mechanisms that underlie the early loss of the male reproductive function are still unknown. Therefore, investigation of this problem is an important task. The medial preoptic nucleus takes part in the regulation of sexual behavior; however, the role of glycine transmission in this nucleus has not yet been stud ied. Our study focuses on these questions.

Lobachevsky State university of Nizhni Novgorod, 23 Prospekt gagarina, Nizhny Novgorod, 603950, Russian FederationThe aim of the investigation was to study the astroglia functional activity in hippocampal slices of the rat at different postnatal development stages by modeling metabolic changes in the brain.Materials and Methods. The study was carried out on hippocampal slices of Wistar rats of three age groups: postnatal days 5-10, 10-20, and more than 20 days of animal postnatal development using a functional calcium imaging method.Results. In early developmental stages, normal astroglial calcium activity was found to require additional energy substrates. Changing the brain metabolic state at low temperature had no significant effect on astrocyte calcium activity in all postnatal periods under study.Conclusion. The study of astrocyte calcium dynamics in different periods of postnatal development can be used as a method to assess functional activity of glial systems when modeling brain metabolic disorders.Key words: astrocyte; calcium responses; specific energy substrates.For contacts: Lebedeva Albina Vladimirovna, e-mail: lebedeva@neuro.nnov.ru Astroglia is the most numerous glial cells performing a number of critical functions in brain. Astrocytes participate in potassium ion buffering, and regulate local blood flow causing vasoconstriction or vasodilatation. Trophic factors expressing in astrocytes have an effect on neuron growth and the formation of new synapses. Astrocytes have great importance in neuron nourishment by supplying them with glucose and other substances that can serve as energy substrate for neurons [1]. They can also be the main glycogen depot in brain [2].Astrocytes are electrically inactive cells, though they have their own signal system presented by the generation of calcium responses, the duration of which can be up to several seconds [3]. Recent studies [4] have shown astrocytes to be of importance in memory formation by lactate delivered to neurons. In active neuronal work, as well in some nervous system pathologies, lactate is synthesized in astrocytes, lactate being the source of energy for neurons. since neuronal activity depends on availability of energy substrates, the process can also be considered as a mechanism used by astrocytes to regulate neuronal functioning [5].lactate and pyruvate are basic energy substrates in a developing brain, as well as in adult brain, if glucose level is low [6]. moreover, ketone bodies [7] have been shown to act as an energy substrate in the brain of The aim of the investigation was to study the effect of brain metabolic changes such as the age of animal postnatal development, temperature conditions, and the presence of specific energy substrates, on functional (calcium) astrocyte activity in rat hippocampus.