In the presented work on the model of artificial desynchronosis, the activity of enzyme aspartate aminotransferase in the mitochondrial fraction of the brain structures was studied taking into account their morpho-functional features. The object of the study is three-month-old Wistar male rats weighing 280-300 g. The experimental model of desynchronosis was created by keeping animals in conditions of a 24-hour light and dark regime for 20 days. According to the results obtained, keeping animals under dark conditions leads to the activation of AST in the tissue and mitochondrial fraction of all the studied brain structures, most pronounced in the hypothalamus (92 and 84%, respectively, relative to the control). The light regime also contributed to an increase in activity in all the structures, significantly expressed in the hypothalamus (105 and 116%, respectively, relative to the control). Significant enzyme activation in all brain structures can be considered as a protective-compensatory mechanism for maintaining a certain level of protein-energy metabolism in the nervous tissue, as well as preserving the structural plasticity of neurons due to the transamination reaction.