Synchronization of excitable cardiac cultures of different origin.

In the present work, we investigated the synchronization of electrical activity in cultured cardiac cells of different origin put in direct contact. In the first set of experiments synchronization was studied in the primary culture cells of neonatal rats taken at different developmental ages, and in the second - in the neonatal rat cardiomyocytes and HL-1 cells. The electrical excitation of cells was recorded using the calcium transient marker Fluor-4. In the confluent cell layers created with the aid of a specially devised mask, the excitation waves and their propagation between areas occupied by cells of different origin were observed. On the level of individual cells, their contact and synchronization was monitored with the aid of scanning fluorescence microscopy. It was found that populations of cultured cells of different origin are able to synchronize, suggesting the formation of electrical coupling between them. The results obtained may be considered as a proof of concept that implanted alien grafted cells are able to create electrical coupling with the host cardiac tissue.

[Rhythmical processes in the cerebral cortex bioelectrical activity in arousal reaction: qualitative nonlinear analysis involving refractoriness]. / Ritmicheskie protsessy v bioélektricheskoi aktivnosti kory golovnogo mozga pri reaktsii aktivatsii: kachestvennyi nelineinyi analiz s uchetom refrakternosti.

An integral equation that takes into account the absolute and relative refractory periods of cortical cells was added to the earlier obtained integral equations describing the cooperation of excitatory and inhibitory neurons of the cerebral cortex, and its substantiation was suggested. The steady states and the stable region of oscillations of the mean membrane potential of excitatory neurons were investigated depending on the mean afferent influx value on the assumption of the normal threshold distribution of cells. The existence of a parameter multitude in the region of stability was shown when a suppression of the delta-rhythm and an enhancement of the theta-rhythm up to its dominance take place increasing nonspecific afferent influx, which shows up a white noise, and decrease of the theta-rhythm during further increase in nonspecific activation. Simultaneously the frequencies of the major cerebral rhythms increase. The conformity of the theoretically calculated dependences of changes of the spectrum upon increasing nonspecific afferent influx to the experimental data obtained during the electrical stimulation of the rabbit midbrain reticular formation was demonstrated.

Electrical activity of isolated rabbit cerebral cortex after direct application of acetylcholine.

Six weeks after surgical isolation of an extensive region of the rabbit neocortex, chronic experiments were carried out to study the EEG spectrum in baseline conditions and after macroapplication of acetylcholine (ACh) to the isolated cortex. Application of ACh elicited a complex, multiphasic response in the sensorimotor and visual regions of the isolated cortex, which lasted more than 10 min and consisted of an increase in the EEG amplitude with a gradual alteration in rhythmicity: there was an increase in theta activity, and higher-frequency (up to 15 Hz) processes appeared in the EEG trace. In control experiments (rabbits with intact cortex), application of ACh increased the EEG spectral amplitude and peak height. The response of the isolated cortex was interpreted as artificially induced activation, the level of activation determining the EEG spectrum. The differences in the responses of the isolated cortex and intact cortex result from preservation of control of the intact cortex by subcortical structures.

[The electrical activity of the isolated rabbit cerebral cortex after acetylcholine application]. / Elektricheskaia aktivnost' izolirovannoi kory golovnogo mozga krolika posle applikatsii na nee atsetilkholina.

Within 6 weeks after surgical isolation of a wide area of the rabbit neocortex EEG spectra were studied before and after acetylcholine application to the isolated cortex. Acetylcholine application initiated an intricate multiphase reaction in the sensorimotor and visual areas of the isolated cortex which lasted for more than 10 minutes. It consisted of an increase in EEG amplitude and progressive change in EEG rhythms, i. e., enhancement of the theta-waves and appearance of higher frequencies (up to 15 Hz) in the EEG. In the control series of experiments (rabbits with the intact neocortex) acetylcholine application produced an increase in EEG amplitude and enhancement of peaks in EEG spectrum. The response of the isolated cortex is interpreted as an artificially induced activation. The distinctions between responses of the isolated and intact neocortex are explained by retention of subcortical control over the state of the intact cortex.

Effect of serotonin and acetylcholine on electrical activity of the isolated rabbit cortex.

Neuronal isolation of the rabbit cerebral hemisphere shifts the EEG spectrum in the direction of slower processes. Application of acetylcholine to the cortex brings about EEG activation and appearance of the theta rhythm. Initially serotonin application is accompanied by the appearance of theta rhythm periods; during subsequent administration of the drug these periods are gradually substituted by slow delta waves. Combined application of serotonin and acetylcholine to the isolated cortex brings about bursts of high amplitude activity, abruptly substituted by "silent" phases. In contrast to the intact cortex, where serotonin brought about prolonged and rhythmic alternation on the EEG of phases of high amplitude activity and of silent periods, in the isolated cortex the bursts of activity of about 1 min duration appeared only after application of acetylcholine to the serotonin-saturated cortex. Repeated phases of activation were either absent or of short duration and were rapidly extinguished.

[Effect of serotonin and acetylcholine on the electrical activity of isolated cortex in the rabbit]. / Vliianie serotonina i atsetilkholina na élektricheskuiu aktivnost' izolirovannoi kory krolika.

Neuronal isolation of the rabbit's cerebral hemisphere shifts the EEG spectrum in direction of slower processes. Application of acetylcholine on the cortex elicits EEG activation and appearance of the theta-rhythm. Initially serotonin application is accompanied by the appearance of the theta-rhythm periods; in the process of subsequent administration of the drug these periods are gradually substituted by slow delta-waves. Combined application of serotonin and acetylcholine on isolated cortex elicits bursts of high-amplitude activity, abruptly substituted by "silence" phases. In contrast to the intact cortex where serotonin elicited prolonged and rhythmic alternation on EEG of phases of high-amplitude activity and of "silence" periods, in the isolated cortex the bursts of activity of about 1 min duration appeared only after application of the acetylcholine to serotonin-saturated cortex. Repeated phases of activation were either absent or were of short duration and extinguished rapidly.

[Cross-correlation analysis of spontaneous spike activity of neurons of the isolated cerebral cortex]. / Krosskorreliatsionnyi analiz spontannoi impul'snoi aktivnosti neironov izolirovannoi kory golovnogo mozga.

Correlation of neuronal impulse activity was studied in the visual and sensorimotor areas of the intact and chronically isolated rabbit cortex. Summate crosscorrelation function of neurones activity of the isolated cortex possess an a symmetrical bimodal form with positive significant deviations in both branches. Summate crosscorrelation function of cells activity in the intact cortex has a significant deviation only in the right branch. The possibility of transmission of excitation through the isolated and intact cortex is suggested and discussed.

[Spontaneous spike activity of neurons of the isolated cerebral cortex in the rabbit]. / Spontannaia impul'snaia aktivnost' neironov izolirovannoi kory golovnogo mozga krolika.

Using the method of correlation analysis, spontaneous impulse activity of isolated cortex (IC) was studied in late terms of isolation (6-9 weeks). It was shown that most of IC neurones (about 70%) had a burst-group type of activity characterized by alternation of irregular long periods of activation (up to a few seconds) and similarly irregular prolonged periods of inhibition. A scheme of spontaneous impulse activity formation in IC is suggested.