Fig. 1.

Motor recovery is impaired and there is accelerated onset of cognitive impairment in aged versus young adult C57BL/6 mice following stroke. a Study design: 3 and 18 month-old (mo) C57BL/6 mice were assessed on the ladder rung and object relocation tests prior to a distal hypoxic (DH) stroke or sham surgery at the indicated timepoints. Following behavioral testing, mice were euthanized and brains were harvested for histology and immunostaining at either 8 or 12 weeks post-surgery. b Motor ability on the ladder rung test was assessed at 1 week pre-surgery, and at 2 days, 2 weeks, 4 weeks, and 6 weeks post-surgery. At 1 week prior to a stroke, there was no difference in motor performance between 3 and 18 mo mice, as both age groups displayed a similar number of correct (nearly 100%) foot placements on the rungs. At 2 days and 2 weeks post-surgery, 3 and 18 mo stroked mice exhibited a motor deficit, as both age groups displayed a significantly fewer number of correct foot placement relative to age-matched sham mice. However, at 4 and 6 weeks post-surgery, 3 mo stroked mice exhibited motor recovery, as they displayed an indistinguishable number of correct foot placements as age-matched sham mice, which was once again nearly 100% correct. 18 mo stroked mice, however, continued to exhibit a motor deficit relative to age-matched sham mice at 4 and 6 weeks post-surgery. c Cognitive function using the object relocation test was assessed at 1 week pre-surgery, and at 1 week, 4 weeks, and 7 weeks post-surgery. At 1 week prior to a stroke, there was no difference in cognitive function between 3 and 18 mo mice, as both age groups displayed significantly more interactions (sniffs and rears) with moved (novel location) verses unmoved objects relative to age-matched sham mice. However, at 4 weeks post-surgery, the 18 mo stroked mice exhibited cognitive dysfunction, as they were now interacting with the two sets of objects equally, indicating that they could no longer distinguish between the moved and unmoved objects. Not until 7 weeks post-surgery did the 3 mo stroked mice exhibit cognitive dysfunction. Data represent mean ± SEM. *p<0.05, **p<0.01, ***p<0.001, and ****p<0.0001