Impaired behavioural flexibility related to white matter microgliosis in the TgAPP21 rat model of Alzheimer disease

In this study, 7 – 8-month-old male TgAPP21 rats were tested for behavioral flexibility, learning, and memory using an operant conditioning chamber and the Morris Water Maze (MWM). TgAPP21 rats demonstrated a regressive behavioral inflexibility during set shifting in an operant conditioning chamber (regressive errors η2 = 0.32 and number of errors after criterion η2 = 0.33). Regressive behavior was also demonstrated in the MWM probe test, wherein TgAPP21 rats significantly increased their swim time in the target quadrant during the last third of the probe test (43% vs 33% in the first 2 thirds of the probe test or the Wt rats’ 29% – 32%); this behavioral phenotype has not been previously described in the MWM. TgAPP21 demonstrated further impairment of behavioural inflexibility as they committed a greater number of reversal errors in the operant conditioning chamber (η2 = 0.30). Diffuse microglia activation was increased in the white matter tracts of TgAPP21 (corpus callosum, cingulum, and internal capsule; η2 = 0.59 – 0.62), which was found to correlate with the number of reversal errors in the operant conditioning chamber (R2 = 0.42). As TgAPP21 rats do not spontaneously develop amyloid plaques but have been shown in previous studies to be vulnerable to the development of plaques, these rats demonstrate an important onset of cognitive change and inflammation in the pre-plaque phase of AD. TgAPP21 rats are also an instrumental model for studying the role and mecha...

Source: Brain, Behavior, and Immunity - February 15, 2019 Category: Neurology Source Type: research