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Volga Neuroscience School 2016 Astroglial control of rhythm genesis in the brain
pal cultures and, as a consequence, a complete inhibition of spontaneous bioelectrical activity of neural networks up to day 7 of the posthypoxic period. Preventive GDNF 1ng/ml application eliminates the negative hypoxic effects by increasing cellular viability as well as by maintaining the functional characteristics of neural networks.
Evaluation of the network structural changes by using the method of correlation analysis showed that hypoxia leads to simplification of the internal structure of neural networks in primary hippocampal cultures: there was a significant decrease in the number of active electrodes as well as in the average number of connections per electrodes (before: 4,22 ± 0,48; after 2,69 ± 0,41) on day 3 after hypoxia modeling. Moreover, the time of signal transmission from electrode to electrode was increased in 4,6 times (p<0,05, ANOVA).
Changes in the functional structure of network burst towards a simplification could be explained by loss of the part of functionally important neurons. Preventive GDNF application contributes to maintaining a complexity of network architecture: at constant/minor increase of the number of active electrodes an average number of connections on the electrodes is significantly reduced, a large value of electrodes with a low number of connections is detected, the amount of hubbs is decreased whereas the time of signal transmission is significantly higher than in the intact group (p <0,05 ANOVA).
To evaluate the possible molecular mechanisms of GDNF neuroprotective action, the GDNF influence on the expression of mRNA GluR2 subunit of AMPA-receptors was investigated. It was shown that hypoxia reduced the expression of mRNA GluR2 in primary hippocampal cultures whereas a preventive GDNF 1ng/ml application negates this effect, contributing to the increase in the number of mRNA GluR2 positive cells. Therefore, GDNF is able to influence on synaptic plasticity under stress conditions.
Acknowledgements
The research was supported by grants of the Russian Foundation for Basic Research 16-34-00301, 16-04-00245 and prepared as a part of the state project "Provision Scientific Research".
Network Ca*- Cell Activity Field CA3 Hippocampal Slices of Rat Early and Late Postnatal Development
Y.I. Mitaeva1 *, A.M. Mozherov1,I.V. Mukhina1'2
1 Lobachevsky State University of Nizhny Novgorod, Nizhny Novgorod, Russia;
2 Novgorod State Medical Academy, Nizhny Novgorod, Russia. * Presenting e-mail: yasya13@mail.ru
Hippocampus - the structure of the central nervous system, which is involved in the mechanisms of emotion and memory consolidation. The hippocampus has a certain topology distribution of cellular elements, which provides the many cellular networks. One of them is the network of neurons in the CA3 field. This network receives inputs from cells of the entorhinal cortex and the dentate gyrus, in addition CA3 pyramidal neurons form the connection between themselves and interneurons, forming a closed network that operates in conditions of acute slice and generates spontaneous Ca2+ activity. Neuronal network interacts with the glial network, the main manifestation of activity which is Ca2+ oscillations. Therefore, to estimate the age dependence of Ca2+ activity in the cells were investigated Ca2+ oscillations in neuronal and glial networks and the interactions between them. In this work, we investigated changes in the characteristics of Ca2+ oscillations cells of rat hippocampal CA3 field in early (P5-8, P14-16) and late (P21-25), postnatal development. Also shown the effect of temperature of perfusion solution on cells Ca2+ activity of CA3 field hippocampal slices of rats in different postnatal periods. Besides in the study was valued role of network activity in the formation of spontaneous Ca2+ oscillations cells of rat hippocampal CA3 field in early and late stages of postnatal development.. Experiments were carried out on acute hippocampal slices from rats. Was used laser scanning confocal microscope Carl Zeiss LSM 510 Duoscan (Germany). Recording fluorescence kinetics were carried out in full frame (field of view of 400x400 mm), with a resolution of 256x256 pixels digital and scanning frequency of 1 Hz. Fluorescence indicators recorded in the range 500-530 nm (Oregon Green488 BAPTA-1 AM) and 650-710 nm (Sulfor-hodamine 101). The fluorescence intensity (s.u.) shows the dependence of the concentration of [Ca2+]i in time, indicating the metabolic activity of cells. Method of cross - correlation analysis was used to evaluate synchrony of Ca2+ oscillations cells of CA3 field of rat hippocampus. We chose the time interval size in 3 seconds and within this interval were found synchronous Ca2+ oscillations in all possible pairs of cells. Further, the number of synchronously occurring Ca2+ oscillations were normalized to the minimum number of Ca2+ oscillations in one of the cells analyzed pairs. The studies have shown that the parameters of cell Ca2+ oscillations field CA3 of hippocampal slices vary depending on
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Volga Neuroscience School 2016 Astroglial control of rhythm genesis in the brain
the period of postnatal rats. Reducing the amount of Ca2+ oscillations with age due to the formation and complexity of synaptically connected neural networks, the transition of electrical synapses in the chemical. Transitional period is 14-16 days of postnatal development, and for 21 days - there is a fully formed neural network. Electrically connected network is weakly controlled, excitement is freely distributed over the network, involving work of all cells, resulting in a high Ca 2+ activity in rat hippocampal cells of younger age group. In mature hippocampal brain slices spontaneous Ca2+ activity with low due to lack of active neural network. In this case, the spontaneous Ca2+ oscillations are due mainly metabolic activity of cells has been shown in our experiments. This study showed that changes in Ca2+ activity in the cells of rat hip-pocampal CA3 fields occurring during postnatal development directly related to the functioning of the neural networks, and the metabolic state of the cells. Ca2+ signaling in mature brain - is a complex multicomponent process involving various receptor systems capable of mutual substitution in violation of the normal functioning of one or more of them.
Acknowledgements
This work was supported by Grant of the President of the Russian Federation for young scientists and graduate students engaged in advanced research and development in priority areas of modernization of the Russian economy for 20152017 (^-1531.2015.4).
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