Assessing recognition memory in a rat model of Alzheimer's disease in the Y-maze

Abstract

Among many features, Alzheimer's disease is characterized by an increase of the beta-amyloid peptide 1-42 (A-beta 1-42) level in the brain as well as by an alteration of the episodic memory. Recognition memory, as a subdivision of episodic memory, is of particular interest for research in the field of Alzheimer's disease. In this context, it is important to establish validated methods to evaluate recognition memory in animal models of Alzheimer's disease, e.g. A-beta injection. Additionally, when realized in a Y-maze, recognition of objects has been described to be less dependent on spatial information. Bilateral intra-cerebroventricular injection of A-beta 1-42 peptide in rats was used as a model of Alzheimer's disease. To test efficacy of an A-beta aggregation inhibitor, animals were co-injected with A-beta 1-42 and the A-beta aggregation inhibitor. Following, memory capacity was evaluated in an object recognition test. Here, we used a new method to assess the rat's preference for the novel object, i.e. recognition memory performance in the Y-maze. A new parameter is used, i.e. time spent in half-arms where the objects are placed, and data are recorded via a video tracking system. First, our results show that the rats' memory performance measured in the object recognition test performed in the Y-maze is altered when measured 2h after A-beta injection. Second, this acute effect can be reversed by the co-injection of compound A, an A-beta aggregation inhibitor. Altogether, these results indicate that the Y-maze version of the object recognition test is enough sensitive to assess memory capacity in a rodent model of Alzheimer's disease, and to evaluate efficacy of an inhibitory substance. Therefore, this new method to assess object recognition is as sensitive as the classical object recognition tests, but provides as well advantages when compared with these more classical approaches, e.g. memory assessment is more specific, the parameter used is easier to define, and using a video tracking system makes the task faster to conduct as well as experimenter independent.