Today the biological effects and terms of the application of caffeine-containing substances are well-known, as well as their chemical composition and the way of transformation in the body. The spectrum of such research is due to a high proportion of consumption of these substances in the human population. This applies particularly to long-term monitoring caffeine-containing effects of substances on health. The relevance of the present study has been determined by observations and related to the analysis of the main characteristics of rats' corticogram under chronic caffeine load.

Experiments were carried out on non-linear white male rats. The first group consisted of control animals (n = 22). The second group (n = 24) was represented by the animals that were given a pure caffeine in an amount of 150 mg/kg/day (LD50) with their meal. The registration of electro corticogram (EKoG) was carried out in conditions of the acute experiment, every 2 weeks for 12 weeks. Background electrical activity was recorded from the motor area of the cerebral cortex. The spectral (mkV2) and the normalized power (%) EGG waves were analyzed within the common frequency band.

Delta-like activity remained dominant throughout the research time in total ECoG of rats from the experimental group. General Dynamics was biphasic. The maximum values of spectral power have been reported after 2 weeks of research (48,52 ± 5,36 mkV2) and the minimum – after 8 weeks (19,27 ± 2,14 mkV2). However, these figures were significantly (р < 0,05) higher than the corresponding value of the control only at the beginning of the experiment (2–4 weeks). Indicators of normalized power in the frequency range of 0,5–3 Hz gradually increased in ECoG total of 62 % (2 weeks) to 74–78 % (10–12 weeks) and were similar to the controls. The theta-like activity of rats from the experimental group expressed by three times less in total ECoG, its power of spectral was significantly (р < 0,05) greater than the control only after 2–4 and 12 weeks of the study. The dynamics of both spectral and power-normalized alpha-like activity of rats of caffeine group was similar to the dynamics of theta rhythm. High-frequency rhythm (13–35 Hz) was least pronounced over the entire study period. This model ECoG may be associated with the increased activity of the neurotransmitter of synthetic presynaptic and postsynaptic decrease threshold excitation of neurons. This is due to caffeine blockade of intracellular phosphodiesterases, stabilization of c-AMP and activation of caffeine receptors and Ca++ release from cellular endoplasmic reticulum.

From our point of view, synaptic plasticity in the central nervous system is formed by self-regulating reactions, which are typical or universal by nature. The end of this chain reaction is the nature of presynaptic quantization and, according to which, synchronous or asynchronous response postsynaptic potential in a certain pattern of gradual responses. More likely impact mechanism is caffeine initial release of Ca++ from intracellular stores endoplasmic reticulum resulting excitation ryanodine receptors, and – blocking phosphodiesterase, all of which leads to activation of the metabolic activity of presynaptic neurons. Obviously, I phase of the experiment clearly demonstrates the significant increase in activity of neurotransmission, manifested increase of power and representation of major slow-low ECoG rhythms. Starting from the 6th week of the experiment, the situation has changed in favor of low amplitude rhythms high-frequency.

This progressive asynchronous may be associated with postsynaptic receptor stimulation in conditions high-frequency micro quantization that shows a certain level of differentiation of postsynaptic receptors rats' neocortex.

Article Received 08.11.2016

Keywords: neocortex, caffeine, background electrical activity, rats

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