Several animal models of Alzheimer's disease have been used in laboratory experiments. Intrahippocampal injection of fibrillar amyloid-beta (fAβ) peptide represents one of the most frequently used models, mimicking Aβ deposits in the brain. In our experiment synthetic fAβ1-42 peptide was administered to rat hippocampus. The effect of the Aβ peptide on spatial memory and dendritic spine density was studied. The fAβ1-42-treated rats showed decreased spatial learning ability measured in Morris water maze (MWM). Simultaneously, fAβ1-42 caused a significant reduction of the dendritic spine density in the rat hippocampus CA1 region. The decrease of learning ability and the loss of spine density were in good correlation. Our results prove that both methods (MWM and dendritic spine density measurement) are suitable for studying Aβ-triggered neurodegeneration processes.