The cerebral hemispheres neuropil of rats with experimental nitrite-induced Alzheimer’s type dementia was studied after mesenchymal stem cells (MSC) introduction. Rats were injected with an aqueous solution of sodium nitrite (50 mg/ kg) for 14 (group 1) and 28 days (group 3), and half of them additionally got intravenously MSC (500000 cells per rat) (groups 2 and 4). The control group received saline in the same way. The acetylcholine level, TBA-active substances contents, catalase and superoxide dismutase activities in brain homogenates, and the content of 2,3-diphofoglycerate (2,3- DFG) in erythrocytes were measured spectrophotometrically. Brain slices were stained with Congo red and according to the Einarson method. They were then examined on an Axiostar plus binocular microscope (“Zeiss”, Germany). The optical density of the cerebral hemispheres neuropil had been measured. In all experimental groups, an increase in the content of 2,3-DFG in erythrocytes and an imbalance in the pro- and antioxidant system, oxidative stress development in brain were observed. The neuropil structure of the cerebral hemispheres was changed: we observed focal zones of neurofilaments degeneration and atrophy and amyloid accumulation, especially in group 3. The optical density of neuropil was reduced; this was accompanied by a decrease in the content of acetylcholine. MSC injections resulted in a significant increase in the content of acetylcholine, decrease in the brain oxygen demand and the content of TBA-active substances. Consequently, prolonged sodium nitrite administration leads to the cerebral hemispheres neuropil structure and functional injury. MSC introduction contributes to the improvement of the neuropil morphofunctional state.