INVESTIGATING PLAY FIGHTING IN STRESSFUL HOUSING PARADIGMS: ASSOCIATIONS BETWEEN PLAYER TYPE, STRESS RESPONSE, AND REPRODUCTIVE IMPAIRMENTS

Play fighting represents a key behavioral component in group-housed rats, yet its contribution to the outcomes of social stress paradigms remains unassessed. This study characterized changes in play fighting behaviors over time in two social stress conditions involving crowding. We also evaluated whether play style influences stress-mediated changes in reproductive signaling. Methodology: 56 adult female Wistar rats were exposed to 21 days of high-density housing (HDH; 8/cage, stable groups) or social instability (SIS; alternating days of isolation and HDH, unstable groups). Home-cage behaviors and corticosterone (CORT) were determined at discrete timepoints throughout exposure. Rats (12/stress group) were categorized as high (HP) or low (LP) players to examine if play profiles were associated to the stress response and reproductive impairments. Results: SIS rats performed more nape contacts and pins than HDH rats but showed shorter pins and more passive responses when pinned. HP-SIS rats had significantly heavier adrenal glands than LP-SIS rats and HP-HDH rats, and spent more days in estrus compared to HP-HDH. CORT secretion showed an immediate rise in HDH rats, compared to delayed increase in the SIS group. In both groups, player profiles remained stable over time, but player types showed no other associations to stress or reproductive markers. Conclusions: These findings support play behavior to serve distinct purposes depending on the social context. In unstable social environments (SIS), play fighting may reflect attempts to test and establish social hierarchies. Conversely, in HDH, play may serve an affiliative role, with stressful effects stemming from factors beyond dominance-submissive relationships.