Proceedings of the International scientific and practical conference ―Synergy of Modern Science and Education‖ (February 2-4, 2026) / Publisher website: www.naukainfo.com. – New York, USA, 2026. - 324 p.

106 233% (p < 0.01), respectively. The duration of grooming and the number of fecal boli, which characterize emotionality, on the contrary, decreased by 76% (p < 0.05) and 78% (p < 0.05), respectively. The number of entries into the open arms and the duration of stay in them were lower than in the ―AEL‖ control by 21% and 37% (p < 0.05). Analysis of neurotransmitter content and correlation analysis revealed relationships between cortical GABA levels and grooming duration (r = –0.6, p < 0.05) and the number of fecal boli (r = –0.24, p < 0.05); between glycine levels and the number of head dips (r = –0.24, cortex) and fecal boli (r = 0.28, cortex; r = 0.34, hippocampus); and between serotonin concentration in the cortex and the number of rearings (r = –0.32, p < 0.05). Conclusion. Thus, acute emotional stress under conditions of experimental hyperthyroidism in early ontogenesis caused significant disturbances in behavioral activity, the cause of which was an imbalance of the main inhibitory neurotransmitter systems of the brain in the absence of significant changes in glutamatergic activity of the cortex and hippocampus.