ABSTRACT

The experiments on rats showed that the restriction of the movements' activity for 15 and 30 days leads to changes in the behavioral reactions in the "open field" and to morphological strikes of the cerebral tissues. The decreasing of animal emotional reactivity and interest to the environment and increasing of anxiety were noticed. Diazepam (0,1 mg /kg intraabdominal) during first 7 days and pyracetam (20 mg/kg intraabdominal) during the whole experiment, as well as electrostimulation of the muscles of the lower extremities essentially improve the rates of experimental animals' cerebral function and show the certain adaptogen and cerebroprotective action.

INTRODUCTION

The restriction of the movements' activity is one of the important factors of risk in the development of the cardiovascular diseases in epoch of the rapid development of science and technology (1) (5). Existing points of view on the problems of the development of the adaptive and pathological changes in the organism under the influence of the hypokinesia are not synonymous and sometimes are controversial. This fact creates additional difficulties for the development of the prevention principles, treatment and correction of consequences of the hypokinetic stress that has a very important meaning for practical and theoretical medicine. Studies that have been conducted in our laboratory (1) (2) (7) for the last couple of years are devoted to the inquiry of the influence of moving activity restriction on the organism, particularly on the regulation of the cerebral blood flow, different sides of the cerebral metabolism and the necessity of their pharmacological correction needs to be verified. Simultaneously, the problem of sensitivity changes of organism to the remedies appears under the condition of hypokinesia, but the studies about pharmacotherapy during hypokinesia are relatively scanty and related to the restricted cycle of drugs (3) (13). The problem of the influence of hypokinesia on the psychological conditions of human and behavioral reactions of animals is not highlighted completely in the literature (8) (12). The aim of this study is to review the influence of the pharmacological and physical actions on the behavioral reactions and morphology of white rats' cerebral tissues during the restriction of moving activity of different duration.

MATERIALS AND METHODS

The experiments were conducted on 39 white unbreed male rats. Hypokinesia was made by locating the rats into the cages, restricting their moving activity for 15 and 30 days. Animals were divided into following groups: I (10 rats) - intact animals, which received 1 ml physiological solution by intraabdominal way; II, III (15 and 14 rats respectively) -animals, that were in hypokinesia condition during 15 and 30 days. In II and III groups 5 rats were chosen (IIa and IIIa), that received diazepam in dosage of 0,1mg/kg intraabdominally during first 7 days and pyracetam in dosage of 20mg/kg intraabdominally during the whole staying under the hypokinesia conditions, as well as electrostimulation of lower extremities were conducted by rectangular impulses with amplitude of 5 Volt, frequency 20 Hz, by the duration of 5msec during 3 min daily. For the study of the cerebral tissues conditions the bits of brain were fixed in 10% buffered formalin by Lilly and covered by paraplast. Slices of 9 mkm thickness were painted by hematoxylin and eosin, kresil violet by Nissle (9). Cerebral parts were marked using the stereotaxic coordinates of rats' brain. The study of the behavioral reactions was conducted by the testing methods in "open field" (4). The frequency of the visits to peripheral and central quarters, frequency of the "exploration of holes", number of rats dropping were registered, as well as the possibility of the animals to save the equilibrium was tested. Pyracetam and diazepam of Polfa (Poland) were used during the experiments. The Wilkokson-Mann-Whitney nonparametric U-criteria was used for statistical analysis of dates.

RESULTS AND DISCUSSION

Literature dates on the attempts of disorders' correction during the hypokinesia are devoted basically to the certain groups of remedies or physical influence (1) (6) (11). Benzodiazepines, barbiturates, neuroleptics, adaptogens, GABA etc. were mentioned more frequently. Analysis of this works, as well as the results of our previously performed studies (1) (2) have shown that the most effective correction could consider pathogenic mechanisms, and phase changes during the hypokinesia, as well as the changes of organism's sensitivity to the remedies. Many authors mentioned the initial "stress" phase, as well as the phase of some adaptation and "picking", which correlated with deep, sometimes irreversible changes in the organisms. Offered stage schema is the result of continuous studies in this area. The hypokinesia during the 15 and 30 days leads to the authentic reduction of frequency of visits to peripheral and central quarters; the reduction of quantity of "explored cage" is also observed (table 1). These results witness that the prolonged staying of animals in narrow boxes leads to the reduction of animals' emotional reactivity and interest to the environment and increasing of fear. Simultaneously, it is necessary to mention that rather stable ability of animals to save an equilibrium is observed on 15th day, as well as on 30th day of the study, which is possibly explained by the less sensitivity of "older" structures of central nervous system to such influences.

The applying of complex actions, including pharmacological (antistressor, cerebroprotective and antihypoxic) as well as physiotherapeutic actions, correlates with significant improvement of rates, especially on 30th day of experiment, which is displayed by the increasing of animals' emotional reactivity and interest to the environment, decreasing of fear and anxiety (table 1).

The local edema of cerebral tissues, especially in basal parts, is observed during the morphological studies of the cerebral tissues of II rats' group (on the 15th day of hypokinesia). Vessels of pial brain tunic are enlarged and full-blooded. There are places with perivascular hemorrhages there. At the same time the neurocytes, especially in V layer of Par1 and Par2 fields of cortex, are hyperchromatic and pyknotic (figure 1). The neuronophagia is often noticed. The chromatophilic substance in pericarion of saved neurocytes becomes crude disperse. The vacuolization and chromatolysis are detected in some neurocytes. The chromatolysis and neuronophagia are often viewed in neurocytes of basal and hypothalamic nucleuses. Vascular plexuses of brain ventricles are enlarged and full-blooded, and the local perivascular hemorrhages are observed. The described changes are common for the mentioned durations of hypokinesia (1) (6) (10). The vessels of pial brain tunic of IIa rats' group contain moderate amount of blood cells. The vessels of cortex are without any particulars, the arteriospasm, enlargement and full-bloodness of veins are noticed in CPu region.

The cytoarchitectonics of cortex is saved predominatingly, spread pyknomorphic changes of neurocytes are detected in the Cg2, Par1 and Par2 fields 2E All cortex layers are involved in Cg2 field, but in Par1 and Par2 fields - mainly neurocytes of V cortex layer. The random small erithrocytar extravazates are observed in pial brain tunic during the long term hypokinesia (III group). The pyknomorphic, as well as hyperchromatic pyknotic neurocytes are noticed, the occurrence of neuronophagia is frequent. These changes are noted particularly in V and VI cortex layer of Par1 and Par2 fields. Moreover, the neurocytes in condition of total chromatolysis are discovered as well. In some cases the massive glial nodules are discovered in cortex (figure 2). It is necessary to mention the existence of neglected zones in V and VI cortex layers. The capillaries of cortex are lessened, the dystonia of veins of small and medium caliber is developed. The perivascular expressed edema is shaped. Neurocytes of thalamic, hypothalamic and basal nucleuses contain the thin disperse chromatophilic substance, which is equally distributed in cytoplasm. Peripheral chromatolysis, neuronophagia and plasmatic saturation of small artery wall are noticed frequently. The epithelium of vascular plexus is flat. Vessels are enlarged and full-blooded. It is of special interest , that in certain cases the vessels' thrombosis is observed. Capillaries are enlarged and sometimes brunched, arteries become windy. Veins are enlarged, full-blooded, the dystonia of veins in form of segmentary narrowing and vasodilatation are noticed (looks like "sand clocks"). IIIa group of rats have not strongly marked full-bloodness of pial veins for the space of hemisphere, especially expressed in basal parts of brain 2E The cytoarchitectonics of cortex is saved. The small groups of neurocytes are observed in Par2, GI AI fields and VI cortex layer, in condition of ischemic homogeneous changes. Neurocytes are well-saved for the rest space. The neurocytes of basal and hypothalamic nucleuses are also well-saved.

CONCLUSIONS

Thus, the offered scheme of complex influence on rats in condition of hypokinesia has a certain adaptogen and cerebroprotective action, which is expressed in significant reconstruction of cerebral blood flow and weakness of the hypoxic damage of brain, that is caused by hypokinesia. The complex experimental therapy during hypokinesia essentially improves the rates of cerebral function of experimental animals.

ACKNOWLEDGEMENTS

This study is a part of scientific theme "The Pharmacological Correction of the Cerebral Blood Circulation Disturbances in Hypokinesia Condition", which is registered in Department of Pharmacology of the Yerevan State Medical University and was supported by Grant N96-905 of the Ministry of Education of the Republic of Armenia. We thank the Prof. Alexander S. Kanayan, chief of the department of Pathology of Clinical Center of the Yerevan State Medical University for valuable help and consultations.

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