Therapeutic ultrasound ameliorates hyperalgesia and edema on CFA-induced persistent inflammatory response in mice

Background: The present study investigated the effects of pulsed and continuous ultrasound (USP and USC) in edema and hyperalgesia after chronic inflammatory process induced by Com-plete Freund's Adjuvant-CFA and analyzing the relationship of the application frequency of ultra-sound, in pro-and anti-inflammatory cytokine production.Methods: Forty-five animals were divided into 9 groups; all animals from groups 2 to 9 were sub-jected to a persistent inflammation model induced by CFA in mice. We report the effects and the underlying action mechanisms of USP and USC in the animals which were irradiated two, three or five times a week on the left hind paw. The analyses performed in this study were: evaluation of hind paw edema through the plethysmometer, evaluation of thermal hyperalgesia through with-drawal test using a water container at 44.5 degrees C (+/- 0.5 degrees C), and the plantar region of the left paw which was removed for analysis of cytokines.Results: Our results showed that USP and USC consistently reduced paw edema, and pulsed ultrasound showed a higher significant effect than the continuous mode. Moreover, groups with irradiation frequency of five times a week presented an inhibition of the edema, and groups with frequency of three or two times a week reduced mainly hyperalgesia, in com-parison with the control group. The beneficial effects of the US then seem to be associated with upregulation of anti-and pro-inflammatory mediators, such as IL-10 and IL-6, respectively.Conclusion: This study provided evidence that ultrasound constitutes an important non -pharma-cological intervention for the management of inflammatory and pain states.(c) 2022 Published by Elsevier Editora Ltda. on behalf of Sociedade Brasileira de Anestesiologia. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).