Modified Recording Chamber for Sustained Kainate-Induced Gamma Oscillations in Submerged Rat Hippocampal Slices

© 2016, Springer Science+Business Media New York.Fast neuronal network oscillations in an in vitro model are a challenging task. Here, we report that sustained gamma (31–35 Hz) oscillations can be induced by kainate (50 nM) in submerged rat hippocampal slices using modified Hájos’s type recording chamber with a superfusion inlet positioned close to the CA3 pyramidal cell layer. The general features of these kainate-induced gamma oscillations were similar to those previously reported in the hippocampal slices using the interface-type chamber and superfused hippocampus in vivo. We suggest that close positioning of the superfusion inlet improves oxygen supply and temperature control of the oscillation-generating network and that this modification could be useful in studies of the gamma rhythmogenesis in the submerged slices

Dynamics of the hypoxia—induced tissue edema in the rat barrel cortex in vitro

© 2018 Juzekaeva, Gainutdinov, Mukhtarov and Khazipov. Cerebral edema is a major, life threatening complication of ischemic brain damage. Previous studies using brain slices have revealed that cellular swelling and a concomitant increase in tissue transparency starts within minutes of the onset of metabolic insult in association with collective anoxic spreading depolarization (aSD). However, the dynamics of tissue swelling in brain slices under ischemia-like conditions remain elusive. Here, we explored the dynamics of brain tissue swelling induced by oxygen-glucose deprivation (OGD) in submerged rat barrel cortex slices. Video monitoring of the vertical and horizontal position of fluorescent dye-filled neurons and contrast slice surface imaging revealed elevation of the slice surface and a horizontal displacement of the cortical tissue during OGD. The OGD-induced tissue movement was also associated with an expansion of the slice borders. Tissue swelling started several minutes after aSD and continued during reperfusion with normal solution. Thirty minutes after aSD, slice borders had expanded by ~130 μm and the slice surface had moved up to attain a height of ~70 μm above control levels, which corresponded to a volume increase of ~30%. Hyperosmotic sucrose solution partially reduced the OGD-induced slice swelling. Thus, OGD-induced cortical slice tissue swelling in brain slices in vitro recapitulates many features of ischemic cerebral edema in vivo, its onset is tightly linked to aSD and it develops at a relatively slow pace after aSD. We propose that this model of cerebral edema in vitro could be useful for the exploration of the pathophysiological mechanisms underlying ischemic cerebral edema and in the search for an efficient treatment to this devastating condition

Microchannel avalanche photodiode with wide linearity range

Design and physical operation principles of new microchannel avalanche photodiode (MC APD) with gain up to 10^5 and linearity range improved an order of magnitude compared to known similar devices. A distinctive feature of the new device is a directly biased p-n junction under each pixel which plays role of an individual quenching resistor. This allows increasing pixel density up to 40000 per mm^2 and making entire device area sensitive.Comment: Submitted to Journal of Technical Physic

Preferential initiation and spread of anoxic depolarization in layer 4 of rat barrel cortex

© 2017 Juzekaeva, Nasretdinov, Gainutdinov, Sintsov, Mukhtarov and Khazipov. Anoxic depolarization (AD) is a hallmark of ischemic brain damage. AD is associated with a spreading wave of neuronal depolarization and an increase in light transmittance. However, initiation and spread of AD across the layers of the somatosensory cortex, which is one of the most frequently affected brain regions in ischemic stroke, remains largely unknown. Here, we explored the initiation and propagation of AD in slices of the rat barrel cortex using extracellular local field potential (LFP) recordings and optical intrinsic signal (OIS) recordings. We found that ischemia-like conditions induced by oxygen-glucose deprivation (OGD) evoked AD, which manifested as a large negative LFP shift and an increase in light transmittance. AD typically initiated in one or more barrels and further spread across the entire slice with a preferential propagation through L4. Elevated extracellular potassium concentration accelerated the AD onset without affecting proneness of L4 to AD. In live slices, barrels were most heavily labeled by the metabolic level marker 2,3,5-triphenyltetrazolium chloride, suggesting that the highest metabolic demand is in L4 when compared to the other layers. Thus, L4 is the layer of the barrel cortex most prone to AD, which may be due to the highest metabolic demand and cell density in this layer

Isolation and identification of promising strains of bacillus subtilis

The article presents data on the isolation and study of the physiological and biochemical properties of Bacillus subtilis cultures. Samples of Chernozem soils of wheat fields were used as materials for selecting crops. 10 isolates with antimicrobial properties of B. subtilis were isolated from the samples. Microscopic observation of these isolates showed that they are gram-positive, rodshaped, endospore-forming bacteria. According to the cultural-morphological and physiological-biochemical characteristics, the isolated isolates were identified as Bacillus subtilis. Work was carried out to study the antagonistic activity of isolated Bacillus subtilis strains to 2 test strains: Alternaria alternata and Fusarium avenaceum. Based on the data obtained, it was noted that Bacillus subtilis strains EU7, EU14, EU22, EU31 and EU34 have antagonistic activity against Alternaria alternata and Fusarium avenaceum. Thus, promising strains for biocontrol of alternarious and Fusarium diseases were obtained

An optogenetic approach for investigation of excitatory and inhibitory network GABA actions in mice expressing channelrhodopsin-2 in GABAergic neurons

© 2016 the authors.To investigate excitatory and inhibitory GABA actions in cortical neuronal networks, we present a novel optogenetic approach using a mouse knock-in line with conditional expression of channelrhodopsin-2 (ChR2) in GABAergic interneurons. During whole-cell recordings from hippocampal and neocortical slices from postnatal day (P) 2-P15 mice, photostimulation caused depolarization and excitation of interneurons and evoked barrages of postsynaptic GABAergic currents. Excitatory/inhibitory GABA actions on pyramidal cells were assessed by monitoring the alteration in the frequency of EPSCs during photostimulation of interneurons. We found that in slices from P2-P8 mice, photostimulation evoked an increase in EPSC frequency, whereas in P9 -P15 mice the response switched to a reduction in EPSC frequency, indicating a developmental excitatory-to-inhibitory switch in GABA actions on glutamatergic neurons. Using a similar approach in urethane-anesthetized animals in vivo, we found that photostimulation of interneurons reduces EPSC frequency at ages P3-P9. Thus, expression of ChR2 in GABAergic interneurons of mice enables selective photostimulation of interneurons during the early postnatal period, and these mice display a developmental excitatory-to-inhibitory switch in GABA action in cortical slices in vitro, but so far show mainly inhibitory GABA actions on spontaneous EPSCs in the immature hippocampus and neocortex in vivo

Rotational dynamics of copper(II) amino acid complexes by EPR and NMR relaxation methods

Rotational dynamics of the copper(II) bis-complexes with glycine and L-aspartic acid has been studied by EPR and NMR relaxation methods in aqueous solutions at several temperatures. Dynamical parameters obtained by EPR were compared with nuclear magnetic relaxation dispersion (NMRD) results and were found to be in a good agreement. From EPR data dominating trans isomer for Cu(Gly)2 and cis isomer for Cu(L-Asp)2 2- was found. On the basis of distance of closest approach of protons to central ion inferred from NMRD and crystal structure data the average slope angles of axial water molecule to equatorial plane were calculated and axial coordination of only one water molecule in the Cu(L-Asp)2 2- complex was established

Layer specific development of neocortical pyramidal to fast spiking cell synapses

© 2016 Voinova, Valiullina, Zakharova, Mukhtarov, Draguhn and Rozov.All cortical neurons are engaged in inhibitory feedback loops which ensure excitation-inhibition balance and are key elements for the development of coherent network activity. The resulting network patterns are strongly dependent on the strength and dynamic properties of these excitatory-inhibitory loops which show pronounced regional and developmental diversity. Therefore we compared the properties and postnatal maturation of two different synapses between rat neocortical pyramidal cells (layer 2/3 and layer 5, respectively) and fast spiking (FS) intemeurons in the corresponding layer. At P14, both synapses showed synaptic depression upon repetitive activation. Synaptic release properties between layer 2/3 pyramidal cells and FS cells were stable from P14 to P28. In contrast, layer 5 pyramidal to FS cell connections showed a significant increase in paired pulse ratio by P28. Presynaptic calcium dynamics also changed at these synapses, including sensitivity to exogenously loaded calcium buffers and expression of presynaptic calcium channel subtypes. These results underline the large variety of properties at different, yet similar, synapses in the neocortex. They also suggest that postnatal maturation of the brain goes along with increasing differences between synaptically driven network activity in layer 5 and layer 2/3

The relative contribution of nmdars to excitatory postsynaptic currents is controlled by ca²⁺-induced inactivation

© 2016 Valiullina, Zakharova, Mukhtarov, Draguhn, Burnashev and Rozov.NMDA receptors (NMDARs) are important mediators of excitatory synaptic transmission and plasticity. A hallmark of these channels is their high permeability to Ca2+. At the same time, they are themselves inhibited by the elevation of intracellular Ca2+ concentration. It is unclear however, whether the Ca2+ entry associated with single NMDAR mediated synaptic events is sufficient to self-inhibit their activation. Such auto-regulation would have important effects on the dynamics of synaptic excitation in several central neuronal networks. Therefore, we studied NMDAR-mediated synaptic currents in mouse hippocampal CA1 pyramidal neurons. Postsynaptic responses to subthreshold Schaffer collateral stimulation depended strongly on the absence or presence of intracellular Ca2+ buffers. Loading of pyramidal cells with exogenous Ca2+ buffers increased the amplitude and decay time of NMDAR mediated EPSCs (EPSPs) and prolonged the time window for action potential (AP) generation. Our data indicate that the Ca2+ influx mediated by unitary synaptic events is sufficient to produce detectable self-inhibition of NMDARs even at a physiological Mg2+ concentration. Therefore, the contribution of NMDARs to synaptic excitation is strongly controlled by both previous synaptic activity as well as by the Ca2+ buffer capacity of postsynaptic neurons

Layer specific development of neocortical pyramidal to fast spiking cell synapses

© 2016 Voinova, Valiullina, Zakharova, Mukhtarov, Draguhn and Rozov. All cortical neurons are engaged in inhibitory feedback loops which ensure excitation-inhibition balance and are key elements for the development of coherent network activity. The resulting network patterns are strongly dependent on the strength and dynamic properties of these excitatory-inhibitory loops which show pronounced regional and developmental diversity. Therefore we compared the properties and postnatal maturation of two different synapses between rat neocortical pyramidal cells (layer 2/3 and layer 5, respectively) and fast spiking (FS) intemeurons in the corresponding layer. At P14, both synapses showed synaptic depression upon repetitive activation. Synaptic release properties between layer 2/3 pyramidal cells and FS cells were stable from P14 to P28. In contrast, layer 5 pyramidal to FS cell connections showed a significant increase in paired pulse ratio by P28. Presynaptic calcium dynamics also changed at these synapses, including sensitivity to exogenously loaded calcium buffers and expression of presynaptic calcium channel subtypes. These results underline the large variety of properties at different, yet similar, synapses in the neocortex. They also suggest that postnatal maturation of the brain goes along with increasing differences between synaptically driven network activity in layer 5 and layer 2/3