Hippocampal volume, social interactions, and the expression of the normal repertoire of resident–intruder behavior

Reduced hippocampal volumes are reported in individuals with disrupted emotional coping behaviors in both human clinical conditions and in experimental animal models of these populations. In a number of experimental animal models, it has been shown that social interactions can promote resilience and buffer the negative neural consequences of stimuli that disrupt effective coping. Methods Hippocampal and dentate gyrus volumes were calculated in 54 male Sprague Dawley rats; (1) single housed ( n  = 12), (2) single housed and exposed to daily 6‐min social interactions testing in a resident–intruder paradigm ( n  = 11); (3) group housed ( n  = 12); (4) single housed and sham injured ( n  = 12); (5) single housed, sham injured, and social interactions tested ( n  = 7). Results We present data which shows that even a brief daily exposure to a conspecific in resident–intruder social interactions test is sufficient to prevent the reduction in hippocampal volume triggered by single housing. Conclusion When considered with previously published data, these findings suggest that the expression of the full repertoire of social, nonsocial, dominance, and submissive behaviors in response to the physical presence of an intruder in the home cage plays a significant role in this maintenance of hippocampal volume.