Avaliação funcional da nocicepção do joelho de ratos tratada com laser de baixa potência e natação

Abstract

This study aimed at evaluating and comparing the effects of low-level laser therapy (LLLT) and a forced swimming training in a joint nociception model on Wistar rats, in order to functionally register pain by observation of paw elevation time (PET) during gait on a metal cylinder. Thirty-two Wistar rats were divided into four groups: CG -untreated animals submitted to nociception induction on right knee; LG -nociception and treated with 670 nm and 8 J/cm2 LLLT; SG -nociception and swimming for 10 minutes in water at 30-32° C; SLG -nociception and treated with swimming and laser. To achieve the nociception, 50 μL of 5% formalin were injected in the medial tibiofemoral space of each animal. Pain was assessed according to a functional incapacity test, which registered paw elevation time (PET) as well as their gait for one minute on a metallic cylinder. The evaluations occurred before nociception induction (EV1), after 15 minutes (EV2) and after 30 minutes (EV3) of it, with treatment protocols being administered after EV2. The analyses showed that LLLT was the only group to present the restoration values in the EV3 when compared to EV1. SG was the only one which did not show any reduction when compared to EV2 and EV3. Hence, it can be inferred that, by functional evaluation, LLLT had some analgesic effects, while the swimming treatment produced pain increase, which was partially reversed by the use of LLLT.

Avaliação do papel de opioides endógenos na analgesia do laser de baixa potência, 820 nm, em joelho de ratos Wistar

“…Laser effects are dosedependent and the expected response is not obtained with it is used in under or overdoses; however, in adequate doses there is effective analgesic effect 11,12 , in spite of a huge discrepancy with regard to adequate dose and wavelength 13 , thus raising the need for other studies to evaluate such dosimetric parameters. Our study has observed that the dose used (8 j/cm 2 ) with 820 nm laser was adequate to induce analgesia as already observed by other study 1 . The evaluation tool used is also referenced in the literature, showing that animals with increased nociception have longer time for flinching while ambulating for one minute, as compared to animals without painful stimulation 14 .…”

“…Pain may be associated to real or potential tissue injury and may cause incapacity by decreasing injured tissue function due to structural injury and tissue edema 1,2 . Low power laser is widely used in therapies especially aiming at decreasing pain 1 and repairing tissues.…”

Effects of the Low-Level Laser Therapy (LLLT) in the process of healing diabetic foot ulcers

“…The results showed that there was the formation of an edema in all of the groups after the injury and that for the treated groups there was a decrease in the edema. Demonstrating that the treatment with low level laser led to a reduction in the edema of the animals with tendinae trauma 17 . That confirms the findings of our research, in which a similar methodology was applied and there was also a decrease of pain with the usage of the low level laser.…”

Avaliação comportamental de ratos treinados em natação forçada

“…A esse estresse também pode ser creditado o efeito analgésico do exercício [16]. Apesar de haver grande semelhança fisiológica, celular e molecular entre os modelos animais e humanos, existem limitações no uso de animais, e a extrapolação de resultados de modelos para humanos deve ser realizada com cautela.…”

“…Ainda, possui ações anti-inflamatórias por ativação imune, que culminam em eventos antidepressivos [14,15]. Contudo, em animais submetidos a modelo experimental agudo de dor articular em joelhos, a natação por 10 minutos não produziu diminuição do quadro álgico [16], provavelmente por causa da pequena duração e intensidade do exercício, visto que, segundo Koltyn e Umeda [17], a hipoalgesia parece ocorrer quando o exercício é realizado em altas intensidades. Ainda, observaram, em camundongos, que a corrida voluntária em esteira gerou aumento na ansiedade, avaliado pelo teste de campo aberto, labirinto elevado e caixa claro/escuro, além de altos níveis de corticosterona nas fezes dos animais [18].…”