FEATURES OF RAT PROTECTIVE BEHAVIOR UNDER ACUTE EMOTIONAL STRESS IN HYPERTHYROIDISM IN EARLY ONTOGENESIS

Abstract

Background. The period of early ontogenesis is extremely vulnerable to the influence of modern stressors. It is known that the thyroid axis is involved in the processes of adaptation, but widespread disorders of its functions require the disclosure of the mechanisms of adaptive response formation under these conditions.

Aim - determination of separate neurotransmitter amino acids and serotonin role in the formation of the central nervous system protective adaptive response in experimental hyperthyroidism and excessive emotional stress at an early age.

Materials and methods. The study was carried out on 30 white outbred rats aged 30-40 days, weighing 40-60 g, which were randomly divided into two groups: “experimental hyperthyroidism” (n=15) and “sham” (n=15). The state of experimental hyperthyroidism was created by administering L-thyroxine with food for two weeks at a dose of 3 μg with a gradual increase relative to the previous one. Behavior was studied in an elevated plus maze and in the Morris water maze. After creating a model of experimental hyperthyroidism and acute emotional stress, animals of both groups were decapitated and the content of neurotransmitter compounds and serotonin were determined according to the standard method. Mathematical processing included the calculation of arithmetic means, standard deviations, and Pearson's correlation analysis.

Results. In rats with experimental hyperthyroidism, a redistribution of motor activity towards staying in unprotected space was found, indicating the anxiolytic effect of thyroid hormones. The additional effect of acute emotional stress led to an excessive increase in vertical locomotion while reducing the number of appearances in open places, weakening of rational and effective anxiety and emotionality, indicating the formation of an anxiogenic state. Studies of the relationship between behavior and neurotransmitter amino acids and serotonin have shown the involvement of the GABA and serotonin inhibitory systems.

Conclusions. The state of hyperthyroidism of rats in early ontogenesis was accompanied by an anxiolytic effect, and additional exposure to emotional stress led to anxiogenicity and memory impairment. The formation of protective adaptive behavior was supported by the participation of neurotransmitter amino acids and serotonin.