Influence of course administration of melatonin on morphological manifestations in the ciliary body of rabbits with experimental hypopinealism

Abstract

Abstract Purpose. The aim was to study the effect of the course of melatonin (M) injections on morphological changes in the ciliary body (CB) of rabbits with experimental hypopinealism. Methodology. The experimental study was carried out on rabbits in compliance with the Law of Ukraine “On the Protection of Animals from Cruelty” No. 3447-IV (Kyiv, 2006) and the "European Convention for the Protection of Vertebrate Animals Used for Experimental and Other Scientific Purposes" (Strasbourg, 1985). Hypopinealism in animals was achieved by keeping them under conditions of round-the-clock illumination (RCI). The groups were: 1) the control group (CG) - 23 intact animals, which were in conditions of natural change of day and night; 2) a group with hypopinealism (HG) - 32 rabbits that were in the RCI; 3) the HG+M group - 29 rabbits that were in the RCI, but before being withdrawn from the experiment, received a course of injections of M for 14 days. Depending on the duration of the experiment, subgroups were identified: a) 3-5 months; b) 8-12 months. The concentration of M in the blood was determined by enzyme immunoassay. A morphological study of the enucleated eyeballs of animals was carried out with a morphometric analysis using the “fields” method. Results. Influenced by RCI night production of M decreased to 62.26±5.27 pmol/l, compared to the control (369.45±14.35 pmol/l; p<0.005). After 3-5 months of RCI, the average relative area of the vessels (ARAV) indicator in the morphometric study in the HG+M3-5 subgroup (15.32±0.37%) is lower than the HG3-5 indicator (17.71±0.43%; p<0.005), and significantly exceeds the indicator CG3-5 (4.70±0.19%; p<0.005); the average thickness of the vascular wall (ATVW) indicator (81.14±3.81×10-6 m) increased compared to CG1-2 (51.31±1.22×10-6 m, р<0.005), and decreased compared to HG3-5 (87.61±3.90×10-6 m; p<0.005). After 18-19 months in the subgroup HG+M18-19, the ARAV indicator decreases to 4.10±0.19%; (p<0.005) and is similar to the indicators of groups CG18-19 and HG18-1(4.22±0.17% and 4.01±0.19%; p<0.05). The indicator of MVWT increased (173.01±6.91×10-6 m), not differing from the HG18-19 indicator (177.51±7.32×10-6 m; p>0.05), but remaining higher than the CG18-19 indicator (101.91±4.42×10-6 m; р<0.005). Conclusion. In animals with M deficiency after 18-19 months of RCI in the CB, the phenomena of vascular hyperemia and dyscirculatory disorders disappear completely, and pronounced sclerotic changes appear. There is a significant thickening of the walls of small arteries and veins due to sclerosis, which leads to a significant increase in ATVW. Vascular desolation is characterized by a significant decrease in the ARAV index. The course of M injections reduces edema and vascular disorders in the early stages of the RCI experiment for up to 5 months. After 18-19 months of RCI, apparently due to irreversible changes in blood vessels, the course of M has no therapeutic effect.