Response of multipolar retinal neurons to photodamage in the experiment

Abstract

Purpose: to assess the reaction of multipolar retinal neurons to light irradiation depending on the intensity and duration of exposure. Material and methods. Outbred sexually mature white rats (n = 50, 100 eyes) weighing 180–200 g were exposed to continuous round-the-clock light (200, 3,500 lux; 1, 2, 7, 14, 30 days). The control group consisted of 25 non-irradiated animals (50 eyes). Using semifine sections, colored with toluidine blue, we counted the number of neurons in the ganglionic layer with karyopyknosis, focal and total chromatolysis. In the optic nerve, the percentage of degeneratively altered axons and the number of nerve fibers with deformation of the myelin sheath were calculated. Ultrastructural changes in neurons were studied using a JEM-100 CX-II electron microscope. Results. In the first days of the experiment (1, 2 days), reactive and destructive changes in organelles are observed in the perikaryons of multipolar retinal neurons. The granular endoplasmic reticulum becomes fragmented, loses part of its ribosomes, and vacuoles of varied sizes are formed from its cisterns. With an increase in the duration of exposure (7–30 days), degradation processes are increasing, all the more so after high-intensity (3,500 lux) light irradiation. The photodamage causes changes in all components of the optic nerve and is characterized by a destruction of organelles, a decrease in the number of elements of the cytoskeleton in the axon, and myelin sheath splitting. Conclusion. Changes in multipolar neurons of the retina after photodamage are primarily related to the content and distribution of the chromatophilic substance and depend on the intensity and duration of illumination.