The involvement of opioidergic and gabaergic systems at the short- and long-lasting effect of early surgical procedure in rats’ nociceptive response

Introduction: Neonates and children are often exposed to pain from invasive procedures during intensive care and postoperative period. Evidence suggests that the exposure to acute pain in early life leads to long-term consequences. Opioid analgesics are the most effective and frequently used substances for the relief of moderate to severe pain in adults and children. The aim of the present study was to investigate the impact of surgical procedures in early life and the involvement of opioidergic and GABAergic pathways on the surgery pain modulation through two different experimental designs: A) experimental design 1 evaluated the short (P21) and long-lasting (P45) effect of early surgical procedure on rats’ nociceptive response; B) experimental design 2 investigated the effect of opioidergic and GABAergic antagonists on surgery pain modulation. Methods: Animals were anesthetized with 2% halothane and submitted to Brennan model of incisional pain. Nociceptive response was evaluated through tail-flick latency test (TFL). Animals from experimental design 2 received naloxone or picrotoxin i.p. 30 minutes before surgery. Results: infant rats (P21) submitted to surgical procedure presented analgesia 30minutes after the surgery. An administration of picrotoxin reverted totally this analgesia at P21/t30 while naloxone was not able to do so. In relation to experimental design 1 animals that had been operated at P21 showed lower nociceptive threshold comparing to the ones that never been operated in life. Conclusions: Early surgical procedure induced short and long-lasting effect upon rats’ nociceptive response. Besides that, an analgesic pattern was presented 30minutes after surgery (at P21), which was only reverted with the administration of picrotoxin. Others studies investigating the impact of surgical procedures in early life and the involvement of pain pathways should be evaluated, due to its importance of being infants and the impact that interventions at this period may cause in these individuals’ adult life.