Effects of resocialization on post‐weaning social isolation‐induced abnormal aggression and social deficits in rats

Abstract

As previously shown, rats isolated from weaning develop abnormal social and aggressive behavior characterized by biting attacks targeting vulnerable body parts of opponents, reduced attack signaling, and increased defensive behavior despite increased attack counts. Here we studied whether this form of violent aggression could be reversed by resocialization in adulthood. During the first weak of resocialization, isolation‐reared rats showed multiple social deficits including increased defensiveness and decreased huddling during sleep. Deficits were markedly attenuated in the second and third weeks. Despite improved social functioning in groups, isolated rats readily showed abnormal features of aggression in a resident‐intruder test performed after the 3‐week‐long resocialization. Thus, post‐weaning social isolation‐induced deficits in prosocial behavior were eliminated by resocialization during adulthood, but abnormal aggression was resilient to this treatment. Findings are compared to those obtained in humans who suffered early social maltreatment, and who also show social deficits and dysfunctional aggression in adulthood. © 2012 Wiley Periodicals, Inc. Dev Psychobiol 56: 49–57, 2014.

Disruption of behavior and brain metabolism in artificially reared rats

“…Affected brain areas are mainly hippocampus, amygdala, nucleus accumbens, thalamus, and medial prefrontal cortex (Sanchez et al, ; Silva‐Gómez et al, ; Lukkes et al, ; Ahern et al, ; Murínová et al, ). All these changes seem reflected in behavioral alterations and disruption of the autonomic system (Grippo et al, ; Lopez et al, ; Tulogdi et al, ). During infancy, many brain circuits are in formation; myelin is just beginning to develop, dendrites are growing, and the brain–blood barrier is establishing.…”

“…Wrong wired or incomplete circuits, mis‐targeted synapses, lack of myelination, under‐ or mis‐development of growth regulatory factors, deficient metabolism of the brain, all of them can be causes for an altered behavior. However, many of these changes have been found with different paradigms of isolation (Fleming et al, ; Min and Nevian, ; Tulogdi et al, ; Sieben et al, ; Wang et al, ; Tanaś et al, ).…”

Mixed housing with DBA/2 mice induces stress in C57BL/6 mice: implications for interventions based on social enrichment

“…Our experiment was carried out in adult female mice and the only finding that could be described as an improvement of social behavior was a decrease of time that DBA/2 mice spent in corner chambers of an IntelliCage (duration of corner visit) during the light period. Mice and rats are nocturnal animals and the inactive period they spend mostly in sleeping in huddle with cage-mates (Tulogdi et al, 2014). The tendency of DBA/2 mice to occupy operant chambers and sleep there alone during the light period can be interpreted as social avoidance and escape to isolated shelters.…”

“…Paired housing with socially active C57BL/6J as cage-mates, but not cross-fostering with C57BL/6J, was effective in improvement of social functions of BTBR adolescent mice (Yang et al, 2007, 2011). Re-socialization (group-housing with normally developed peers) rescued the prosocial deficit induced by post-weaning social isolation in rats (Tulogdi et al, 2014). The effectiveness of group-learning and social enrichment in facilitation of learning and memory was also validated in an animal model of Alzheimer's disease (Kiryk et al, 2011) and in BTBR mice (Lipina and Roder, 2013).…”

Brain regional differences in social encounter-induced Fos expression in male and female rats after post-weaning social isolation

“…Although long-term social isolation that occurs during different periods of development (either neonatally or in adulthood) may also impact behavior, the alterations in social behavior that are produced by PSI are particularly pronounced (Hall, 1998). These alterations are persistent and in some cases irreversible (Tulogdi et al, 2014), and are thought to be largely due to a lack of opportunities for social play during the sensitive period of adolescence. Play is adaptive in the early life of social species including humans and rodents (Panksepp, 1981), allowing individuals to practice the skills needed for proper social conduct and developmentally appropriate behaviors in adulthood.…”