CHANGES IN THE STRUCTURAL ORGANIZATION OF CELLULAR COMPONENTS IN THE RETINAL LAYERS AND LINKS OF ITS HEMOMICOCIRCULATORY BED DURING THE CHRONIC PERIOD OF EXPERIMENTAL OPIOID EXPOSURE AND THE CORRECTION OF THESE CHANGES AT THE ULTRASTRUCTURAL LEVEL

Abstract

Over the past twenty years, the experimental direction of research has been the most relevant in morphology to study the dynamics of the course of nosologies. In terms of the dynamics of the occurrence of pathomorphological manifestations at the cellular, tissue, organ, and organism levels, it off ers a larger variety of pathology investigations. The study of the retina in the norm and the processes of modifying its structural reorganisation under the eff ect of various nosologies are accorded high importance in the scientifi c literature written by both domestic and international professionals. Despite these eff orts, the problem of opioid retinopathy on prolonged experimental opioid exposure remains essential. It is still unknown, in particular, if the correction of the chronic period of experimental opioid exposure may stabilise pathomorphological symptoms in the retinal layers and linkages of its hemomycrocirculatory bed. The purpose of the research is to fi nd out the features of structural reorganization in the retinal layers and links of its hemomicrocirculatory bed in the chronic period of experimental opioid exposure and the correction of these changes with pentoxifylline.Material and methods. The research used 34 male, sexually mature, non-breeding rats that ranged in weight from 160 to 270 g and were 4.5 to 7.5 months old as its subject matter. The correction dose of pentoxifylline was 2.857 mg/kg. At the end of the 10th week, the material was taken for ultrastructural examination of the retina. Before the sampling of the experimental site material, the animal was withdrawn from the experiment using diethyl ether. The eyeballs of rats were used as a material for ultrastructural examination. Ultrastructural preparations were prepared according to the generally accepted method. As a result of our research of the retina at the end of the tenth week in rats, which were injected with an opioid for six weeks, and subsequently discontinued for four weeks, the phenomena of degeneration of the pigment epithelium, destruction of the membrane discs of the outer segments of the photoreceptors, degenerative changes in the inner segments of the photoreceptors, degenerative and necrotic changes of individual photoreceptors developed. Degeneration and necrosis processes were detected in bipolar and amacrine neurons. Rats were injected with the opioid for six weeks, with its cancellation and subsequent four-week correction with pentoxifylline. After ten weeks of the experiment, degenerative changes in the apical microvilli of the pigment epithelium, destruction of the membrane discs of the outer segments of the photoreceptors, degeneration of bipolar and amacrine neurons, moderately pronounced discirculatory changes, and reactive processes of glial elements were detected. In rats given an opioid for six weeks, followed by four weeks of an opioid with pentoxifylline administration, fl ushing, stasis, and perivascular oedema in the choroidal arteries were established ten weeks later. Degeneration and necrosis of the pigment epithelium, degeneration and destruction of the membrane discs of the outer segments of photoreceptors with separation of individual outer segments, degeneration of the inner segments of photoreceptors, degeneration and necrotic changes of photoreceptors, degeneration and necrotic changes of bipolar and amacryne neurons, Muller cells, degeneration of ganglion neurons, hyperemia, stasis and perivasal oedema in the vessels of the ganglion layer, the layer of nerve fi bers, in the inner mesh layer.