We studied changes in the ultrastructure of synapses and myelin nerve fibers that develop in the penumbra in 4 and 12 hours after modeling infarction in the frontoparietal cortex in rats. Ischemic stroke was induced by injection of a photosensitive dye into their bloodstream followed by illumination of the brain surface with a halogen lamp. Visible ultrastructural changes were observed in the penumbra zone, namely in the axodendritic and axospinous synapses; they consisted in polymorphism and disorganization of synaptic vesicles, mitochondrial swelling, swelling and vacuolization of the postsynaptic fragments of dendrites, and shortening and osmiophilia of the active zone. In the presynaptic terminals, clear-cut signs of transformation were not observed during the first 12 hours. It indicates the necessity of early treatment of strokes.

The study of isolated preparations of experimental white rats of 14 months and older reveals that the longitudinal orientation of cardiomyocytes is replaced by an angular orientation in older mice. The number and structural integrity of myofibrils occupy one of the leading places in the regulation of the contraction-relaxation cycle and the implementation of the adaptive capabilities of the myocardium in the normal functioning of cardiomyocytes. Our experimental studies aim at describing the quantitative a n d m o r p h o l o g i c a l c h a r a c t e r i s t i c s o f m y o f i b r i l s i n r a t s o f t w o a g e g r o u p s a n d a n a l y z i n g t h e morphological and functional results. Isolated heart preparations were examined in two age groups of white rats (middle -8-14 years; elderly -14 months and more. The number of rats in each group amounted to six) using different histological staining methods. The results obtained show that, compared with middle-aged rats, the development of degenerative changes in myofibrils is observed in old rats, which is manifested in structural inferiority and quantitative reduction. Degenerative changes revealed with age at the intracellular level can be considered an important morphological basis for the formation of functional heart failure and the depletion of adaptive capabilities.

The aim of the study was to evaluate cardiac functional parameters after 11 weeks of dosed, highintensity exercises on a treadmill in 12-13-week-old healthy rats. In general, physical activity is the cheapest and safest method to reduce cardiovascular disease risk factors (1, 2, 3). Within the scope of Georgian Scientists/ . 4 N 3, 2022 280our study, we subjected 12-13-week-old healthy male rats to high-intensity exercise on a treadmill for 11 weeks and then studied cardiac function parameters by echocardiography to assess the effects of exercise on the healthy heart. The rats were divided into 2 groups: 1) control group, which did not receive any execrise (n=8); 2) The study group performed 10 full rotations on the treadmill per day, with 1-minute active breaks in between, 5 days a week (treadmill speed 19m/min, incline 30 0 ) -n=8.Cardiac function parameters were assessed through transthoracic echocardiography twice (at the start of the study and after 11 weeks). Compared to the control group, there were changes in the functional parameters in terms of improvement in the rats of the study group, in particular, the ejection fraction, stroke volume, left ventricular wall thickness, end-diastolic volume increased, and on the contrary, the end-systolic volume decreased, compared to the data of non-trained rats of the same sex and age.The present study can be considered as another step forward in the study of functional changes of healthy heart developed on the background of high-intensity physical activity.