Abstract:
Experiences with early life pain and stress influence important pain pathways that affect adult pain sensitivity. This research looks specifically at the influences of environmental enrichment (enhancement of the social and physical environments) and neonatal pain on adult pain sensitivity in mice. A sample of 100 mice were divided into surgery, sham surgery or control conditions and were then housed in either an enriched or a standard cage for nine weeks. Testing included pain sensitivity through tail withdrawal; Von Frey filaments, and abdominal constriction tests, stress responsiveness through blood corticosterone measurements after the restraint stressor test, and hippocampal neurogenesis. Findings showed a significant interaction between the surgery condition and environmental enrichment in all pain modalities, suggesting that enrichment modulates the effects of neonatal pain. Corticosterone and neurogenesis results were inconclusive. Future directions include using morphine and naloxone to test initial influences of acute neonatal pain, as well as opioid-knockout mice to elucidate the mechanisms of enrichment in these effects.