Indicators of pain sensitivity threshold in experimental osteoarthritis and hypothyroidism

Diseases of the thyroid gland are an urgent problem of modern society due to a wide, constant spread of this pathology and with somatic, reproductive and mental disorders associated with these diseases. The negative effect of thyroid hormone dysfunction on the functional state of organs and systems is due to the key role of thyroid hormones in metabolic processes. It is known that metabolic disorders in diseases of the thyroid gland negatively affect the state of bone and cartilage tissue and cause the development of a number of pathological conditions among which osteoarthritis is absolutely important. However, to date, the issue of changing the pain sensitivity threshold against the background of osteoarthritis due to functional insufficiency of the thyroid gland, which is of key importance in studying the efficacy and safety of pharmacotherapy of these diseases, is not sufficiently covered. The author studied the changes in pain sensitivity threshold in rats when modeling osteoarthritis and hypothyroidism. In the work 80 rats were used, which were divided into two experimental groups - the control group (n=40) and the group of animals with experimental osteoarthritis and hypothyroidism (n=40). Experimental hypothyroidism was reproduced by enteral administration of a 0.02% solution of carbimazole, which was prepared at the rate of 5 mg per 250 ml of saline and given with a drinking ration of animals for 6 weeks. Experimental osteoarthritis was reproduced by a single intra-articular injection of 0.1 ml of monoiodoacetic acid solution into the knee joint, prepared at the rate of 3 mg of reagent per 50 μl of sterile saline. To assess the threshold of pain sensitivity in rats against the background of experimental models, the method of electrical stimulation of the rat tail was used in the standard method. The pain threshold was determined by the reaction of vocalization during electrocutaneous stimulation of the rat's tail root. Based on the data obtained, conclusions were drawn about the negative effect of the thyroid hormone deficiency on the formation of the pain response in experimental animals, which indicates a weakening of the response to nociceptive effects, is manifested by an increase in the pain threshold.