An intracerebroventricular injection of Aβ-amyloid (1-42) aggregates modifies temporal profiles of spatial memory in rat

Abstract

Alzheimer’s disease (AD) is the major cause of dementia in older people. AD is clinically characterized by a progressive cognitive decline followed by loss of memory. In the present study, we aimed to investigate the consequences of an intracerebroventricular (ICV) injection of aggregated β-amyloid peptide (1-42) on temporal patterns of cognitive functions using a modified version of the Barnes maze test. Four-month-old males Holtzman rats were divided into two groups defined as: control (CO) and Aβ-injected (Aβ). Rats were maintained under 12 h-light:12 h-dark conditions and received water and food ad libitum. The first group received an intracerebroventricular injection of sterile saline solution (5 μL), and the second group received an ICV injection of the solution of Aβ (1-42) aggregated (5 μL). A week after the surgery, Barnes’ test modified was performed to test cognitive functions of the rats during day and night. The parameters assessed were as follows: (a) number of errors; (b) escape box latency; (c) Hole exploration frequency in the goal sector; (d) Total exploratory activity; (e) Path length. In the behavioral studies we used 23 animals from each control group and Aβ-injected groups. Our results demonstrated that Aβ-injected rats showed an increase in the number of errors to reach the target hole at night and exhibited a notable increase in the latent period during day and night, in comparison with control group. During the day, the Aβ-injected group explored less frequently the target sector and in night showed a significantly lower exploratory activity. The total distance walked was affected by the ICV injection of the amyloid aggregates. According to these results, we could suggest that the temporal patterns of spatial memory are altered in animals injected with Aβ and are correlated with the increase in Aβ observed by our group.