Involvement of the opioidergic and nociceptinergic systems in the analgesic effects of novel nociceptin analogues after acute and chronic immobilization stress

Abstract

Stress is known to exert an influence on neuroendocrine, autonomic, hormonal functioning. Various stress models have been reported to induce analgesia. This is a phenomenon, referred to as stress-induced analgesia (SIA). Nociceptin/Orphanin FQ(N/OFQ) is a heptadecapeptide that has been found to play a direct role on pain perception. This study aimed to investigate the effects of novel nociceptin analogues on nociception after acute and chronic immobilization stress (CIS) and the involvement of the opioid and nociceptinergic systems in analgesic effects. Analgesic effects were examined by paw-pressure (PP) and hot-plate (HP) tests. Our data showed that acute immobilization stress induced hypoalgesia. The analgesic effect was more pronounced in pain caused by a mechanical stimulus than by a thermal one. CIS attenuated the hyperalgesic effect of naloxone and JTC-801 for mechanical and thermal stimulation. The effects of the opioid system are more pronounced in acute immobilization stress, while the nociceptin mechanisms predominate after chronic stress.