Social isolation after stroke leads to depressive-like behavior and decreased BDNF levels in mice

• Isolated mice have exacerbated stroke-induced histological injury compared to pair housed animals.
• Locomotion across all stroke mice is equivalent by day 3 in the Open Field Test (OFT).
• Isolation leads to increased immobility in the Forced Swim Test (FST) at 13 days post-stroke.
• Pair-housed animals have increased BDNF levels in stroke tissue at 49 days post-stroke compared to isolated cohorts.

Social isolation prior to stroke leads to poorer outcomes after an ischemic injury in both animal and human studies. However, the impact of social isolation following stroke, which may be more clinically relevant as a target for therapeutic intervention, has yet to be examined. In this study, we investigated both the sub-acute (2 weeks) and chronic (7 weeks) effects of social isolation on post-stroke functional and histological outcome. Worsened histological damage from ischemic injury and an increase in depressive-like behavior was observed in isolated mice as compared to pair-housed mice. Mice isolated immediately after stroke showed a decrease in the levels of brain-derived neurotrophic factor (BDNF). These changes, both histological and behavioral, suggest an overall negative effect of social isolation on stroke outcome, potentially contributing to post-stroke depression and anxiety. Therefore, it is important to identify patients who have perceived isolation post-stroke to hopefully prevent this exacerbation of histological damage and subsequent depression.