Dynamics of morphological changes in the cellular layers of retina in the long-term experimental opioid exposure
Authors: Paltov Ye.V. , Masnа Z.Z. , Fik V.B. , Ivasivka Kh.P. , Chelpanova I.V. 
Published: November 2023

Relevance of research. There is enough information in the foreign and domestic specialized literature on the issue of morphological reorganization of cells and tissues during experimental opioid exposure and other types of toxic effects on the body today. At present, the issue of structural reorganization in the layers of the retina and disruption of its blood supply processes during subchronic and chronic periods of experimental opioid exposure remains unclear. That is why we decided to supplement, expand and deepen information about these processes by conducting our own research in this direction. The purpose of the study is to clarify the dynamics of pathomorphological changes in the layers of the retina and the links of its hemomicrocirculatory channel in the long term of experimental opioid exposure.Material and methods. The research material was sexually mature, outbred, white male rats, 56 animals in number, weighing 160-270 g, aged 4.5-7.5 months. The initial dose of nalbuphine during the first 2 weeks was 0.212 mg/kg, the next 2 weeks (III-IV weeks) – 0.225 mg/kg, the next (V-VI weeks) – 0.252 mg/kg, the next (VI-VIII weeks ) – 0.260 mg/kg, the next (VIII – X weeks) – 0.283 mg/kg, the next (X – XII weeks) – 0.3 mg/kg, and during (XII – XIV weeks) – 0.45 mg/ kg. Before taking the material of the experimental site, the animal was removed from the experiment with the help of diethyl ether. Rat eyeballs were used as a material for ultrastructural research, considering the preservation of the topographic ratio of the eye membranes. Ultrastructural preparations were prepared according to the generally accepted method. Research results. At the end of the eighth week and the tenth week, persistent hyperemia of the choroidal vessels, degenerative and necrotic changes in the cells of the pigment layer, degeneration of the outer segments of photoreceptors, shortening and fragmentation of mitochondrial cristae of the inner segments of photoreceptors, necrotic changes in the nuclei of individual photoreceptors, degeneration of axons of the outer and inner reticular layers, as well as degenerative and necrotic changes of bipolar and amacrine cells, hypertrophy of processes of Müller cells, degeneration of ganglion cells, hyperemia and perivascular edema of vessels of the outer and inner reticular layers were revealed. After twelve and fourteen weeks, the initial stages of development with subsequent progression of sclerotic changes of Bruchʹs membrane were first detected. The phenomena of degenerative and necrotic changes in the cells of the pigment layer, destruction of the membrane of the outer segments of photoreceptors, degenerative changes in the axons of the outer and inner reticular layers and the layer of nerve fibers, degenerative and necrotic changes in bipolar and amacrine cells, hypertrophic changes in processes of Muller cells, hyperemia and stasis gradually increased, perivascular swellings in the vessels of the inner reticular layer, ganglionic layer and layer of nerve fibers, reactive changes in Muller cells and protoplasmic astrocytes. Conclusion. In the long-term course of experimental opioid exposure, irreversible pathomorphological changes occurred and subsequently progressed, which were caused by an increase in dyscirculatory manifestations in the superficial and deep vascular networks of the retina, causing the deepening of edema phenomena with further compression and hypoxia in the thickness of the retinal layers.