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The effects of the ultralow-intensity electromagnetic fields (EMF, frequency of 4200 and 970 MHz, modulated by a quasistochastic signal in the range of 20-20,000 Hz, power density 15 microW/cm2, specific body absorption rate up to 4.5 mJ/kg) on the reactions of the central nervous system (CNS) of rats with different types of behavior were studied. Some neurochemical and behavioral mechanisms of rats' reactions were investigated. It was shown that the EMF produce pronounced changes in the state and activity of monoaminergic brain systems. These changes, on the whole, correspond to the alterations at the integrative level (predominantly, of the inhibitory character).

Behavioral and neurochemical reactions of small laboratory animals (mice and rats of different age) under exposure to ultralow-intensity electromagnetic fields (EMF, frequency of 4200 and 970 MHz, modulated by a quasistochastic signal in the range of 20-20,000 Hz, power density 15 microW/cm2, specific body absorption rate up to 4.5 mJ/kg) were studied. The EMF basically inhibited the locomotor and exploratory activity in the "open-field" test. The species- and age-specific features rather than radiation conditions dominated. However, decrease in the EMF frequency considerably intensified the observed effect. Change in animal behavior was accompanied by shifts in neurochemical processes, i.e., sharp activation of serotoninergic and inhibition of morepinephrinergic system.

In experiments on non-movement rabbits with help specially made from organic glass of micromanipulator and non-artefactions electrodes and wires study the bioelectrical activity separate neurons on moment of package-pulsing microwaves irradiation (1.5 GHz, duration of pulse-0.4 ms, frequency their recurrences 1000 Hz, duration of packs-16 ms, frequency their recurrences-0.12 Hz, energy-0.3 mW/sm2). The results of experiments are compared with control series, where is carried out false irradiation.

A peculiarity of the work is an analysis of bioelectrical activity of single neurones under irradiation with low-level pulsed microwaves (6 GHz, 50 Hz, 0.2 mW/cm2). A specially designed micromanipulator made of organic glass was used. The results are presented in comparison with appropriate reactions of neurones to other physical factors considered like microwaves as weak stimuli for central nervous system.

In experiments with 112 male Wistar rats it was shown that accelerated electrons (85 Gy) caused a significant increase in activities of succinate dehydrogenase (SDG) by 15.8% and lactate dehydrogenase (LDG) by 17.0%, and a decrease in activities of alkaline phosphatase (AP) and monoamine oxidase (MAO) by 10.6 and 7.8% respectively within the sensorimotor region of the cerebral cortex immediately after irradiation. Activity of SDG and MAO decreased (by 16.4% and 7.8% respectively) in the caudate nucleus over the same period of time. An increase in the accelerated electron dose from 85 to 500 Gy did not change the direction and the rate of the radiation response of the enzymes. Exposure of rats to 60Co gamma quanta (75 Gy) increased SDG and LDG activity (by 21.4 and 17.3% respectively) within the sensorimotor cortex as late as 10 min after irradiation. A repeated significant increase in SDG and LDG activity was observed 2 hr after irradiation.

Adaptive processes occurring in white rats in response to microwave irradiation with non-thermogenic density, were studied as well as the maximal working ability of the animals, the impedance of their sensomotor cortex, hypothalamic nuclei and cerebral tissues, skeletal muscles and liver. Probable physiological mechanism of the observed effects is discussed.

Neurocyte nuclei increase in volume without structural changes in karyoplasm at early times after gamma-irradiation of rat head with doses of 50 to 100 Gy. Irradiation of 200 Gy causes a diminution of the nuclei volume while at a dose of 400 Gy the nuclei do not change their volume. A dose as high as 1000 Gy causes severe changes in the karyoplasm leading to nucleus swelling. At later times (24-72 h), the increase in the nuclei volume is associated with the changes in the karyoplasm structure. At one and the same dose, radiation causes either a decrease (irradiation of the head) or increase (exposure of the body) in the neurocyte nuclei volume. At early times after wholebody uniform irradiation no karyometric changes are detected. The nucleus swelling is more pronounced at lower dose-rates.

Using karyometric procedures, the reactions of neuronal nuclei of the middle layers of the sensorimotor cortex of rats exposed to the combined effect of ionizing radiation and longitudinal acceleration or vertical vibration were investigated. It was found that the size of neuronal nuclei varied depending on the radiation dose and the type of combinations of radiation with other exposures.

The overall bioelectrical activity of the sensorimotor and visual brain cortex of rabbits was estimated during early neurological impairment caused by 120 Gy gamma-irradiation. The characteristic changes were revealed in the amplitude, form, energy spectrum and spatial biopotential synchronization. The changes in the bioelectrical activity of the brain were associated with the clinically displayed stages of the neurological process development.

For 24 h after total gamma-radiation of mature Wistar male rats (180-210 g) in the dose of 150 Gy, ultrastructural rearrangements of the cerebral sensomotor cortex are presented as small destructive changes in neurons, neuroglia and vascular endothelium. Total combination of the changes in ultrastructure of the blood capillaries and perivascular astrocytes makes it possible to suppose that permeability of the microvascular bed wall is increased. At this period, together with the destructive changes there are evidently certain compensatory-restorative processes, developing in the cerebral tissue. It is possible to suppose that already during the first hours after the radiation the ultrastructural changes of neurons are resulted not only from the direct effect of radiation, but from certain influences of the radiation damage of neuroglia and microvessels.

It has been shown that the low-level laser radiation with the wave-length in the red part of spectrum changes greatly the activity of the respiratory center under the direct influence on the rats' brain structure. The influence of light may have activating or inhibitory character; sometimes symmetry in the respiratory center activity is disturbed. The difference of the effects under the radiation of the sensomotor area of the cerebral cortex hemispheres and the area of the bulbar respiratory center has been found out. It is supposed that one of the reasons of the functional state of the respiratory center variations is the metabolism change in its structures.

At early times (15 min to 6 h) after whole-body gamma-neutron irradiation of mature rats with a dose of 10 Gy reactive changes occur in neurons of the sensimotor cerebral cortex which can be interpreted as a manifestation of the enhancement of functional and metabolic activity of nerve cells followed by inhibition thereof.