Modeled Behavior of Neuropathic Pain with Social Defect in Rats: A Preliminary Methodology Evaluation

BACKGROUND Social defect and chronic pain are 2 major health problems and recent data has demonstrated that they generally exist concurrently. However, a powerful evaluation model on the behavioral change is lacking. This study was designed to evaluate the behavioral curves using a statistically modeled trajectory analysis in neuropathic animals with or without social defect exposure. MATERIAL/METHODS After approval by the institutional animal care committee, Sprague-Dawley rats were randomized into different interventional groups with 15 animals each. Sprague-Dawley rats underwent spared nerve injury (SNI) to establish the neuropathic pain model, of which the mechanical withdrawal threshold was measured using von Frey filaments for a period of 105 days. Otherwise, a modified version of the resident (Long-Evans rats)-intruder paradigm was applied to produce a social defect animal model through the elevated plus maze (EPM). After raw data collection, we modeled them into a powerful statistical effects analysis to build up the behavioral change tendency in single SNI or in combined SNI and social defect animals. RESULTS The random and fixed effects analyses of the pain behavior after SNI were successfully modeled and demonstrated a gradient recovery tendency during the 15-week post-injury observational period. Correspondingly, SNI rats exhibited increased social defected symptoms, as indicated by the increased anxiety-like behavior in the EPM test. In addition, continuous social defect stress for 5 days or 10 days, respectively, partially attenuated and exacerbated SNI-induced allodynia in both random and fixed effects models. Five days but not 10 days social defect ameliorated SNI-associated anxiety-like behavior. CONCLUSIONS These data suggest that statistically powerful analysis of nerve injury-induced neuropathic pain is a highly sensitive model to determine the behavioral change tendency and distinguish them among behavior curves with or without social defect, and the combination of SNI with resident-intruder paradigm may be a suitable model for behavior evaluation of neuropathic pain with social defect.