Toll-like receptor 9 deficiency impacts sensory and motor behaviors

We report that TLR9 deficient (TLR9−/−) mice show a hyper-responsive sensory and motor phenotype compared to wild type (TLR9+/+) controls. This is indicated by hypersensitivity to thermal stimuli in the hot plate paw withdrawal test, enhanced motor-responsivity under anxious conditions in the open field test and greater sensorimotor reactivity in the acoustic startle response. Prepulse inhibition (PPI) of the acoustic startle response was also enhanced, which indicates abnormal sensorimotor gating. In addition, subtle, but significant, gait abnormalities were noted in the TLR9−/− mice on the horizontal balance beam test with higher foot slip numbers than TLR9+/+ controls. In contrast, spatial learning and memory, assessed by the Morris water maze, was similar in the TLR9−/− and TLR9+/+ mice. These findings support the notion that TLR9 is important for the appropriate development of sensory and motor behaviors.