Progressive impairment of directional and spatially precise trajectories by TgF344-AD Rats in the Morris Water Task

Abstract

Spatial navigation is impaired in early stages of Alzheimers disease (AD), and may be a defining behavioral marker of preclinical AD. Nevertheless, limitations of diagnostic criteria for AD and within animal models of AD make characterization of preclinical AD difficult. A new rat model (TgF344-AD) of AD overcomes many of these limitations, though spatial navigation has not been comprehensively assessed. Using the hidden and cued platform variants of the Morris water task, a longitudinal assessment of spatial navigation was conducted on TgF344-AD (n=16) and Fischer 344 (n=12) male and female rats at three age ranges: 4 to 5 months, 7 to 8, and 10 to 11 months of age. TgF344-AD rats exhibited largely intact navigation at 4-5 and 7-8 months of age, with deficits in the hidden platform task emerging at 10-11 months of age. In general, TgF344-AD rats displayed less accurate swim trajectories to the platform and a wider search area around the platform region compared to wildtype rats. Impaired navigation occurred in the absence of deficits in acquiring the procedural task demands or navigation to the cued platform location. Together, the results indicate that TgF344-AD rats exhibit comparable deficits to those found in individuals in the early stages of AD.