Effect of hyperbaric oxygenation therapy on nociceptive pain

Pain is the main symptom of inflammatory diseases and prostaglandins (PGs) participate in them in an important way. Thus, NSAIDs, which inhibit the PGs synthesis, are the first-choice drugs for that diseases. However, its use is mainly associated with gastrointestinal, hepatic and renal adverse effects. This problem tends to be aggravated because they are freely sold, and the abuse is frequent. On the other hand, there are other alternatives for the pain treatment, one of them is Hyperbaric Oxygen Therapy (HBOT) that has been used empirically for the treatment of various diseases that cause pain, such as migraine, fibromyalgia, among others. However, the knowledge about the mechanism of action is modest. So, the objective of this work was to study the effect of HBO therapy on the formalin model and to compare with the indomethacin or rofecoxib treatment. Therefore, male Wistar rats weighing 150 to 200 g were used, them were divided into four experimental groups: Control, HBOT, Indometacin and Rofecoxib. Drugs or HBOT were applied one hour prior to the administration of 2% formalin intraplantarly. The number of shakes was evaluated for 1 minute every 5 minutes until completing 1 hour of observation. The results obtained indicate that the administration of formalin produces a biphasic hyperalgesic response that decreases as a function of time during the first 10 minutes (phase 1, nociceptive) and subsequently increases until reaching a plateau from 10 to 25 minutes approximately for later and reduce in the following 35 minutes (phase 2, inflammatory). The HBOT or the pharmacological treatment reduced the formalin curve size (p<0.05), mainly in phase 2, and HBO therapy being the most effective. In conclusion, HBO was effective in treating acute pain. In phase 2 an important participation of prostaglandins is corroborated since the NSAIDs used produced an analgesic effect. in the mechanism induced by the HBO, PGs might be participating.