Mecanismos de ação envolvidos na atividade anti-inflamatória e antinociceptiva por meio da radiação laser no acuponto E36 (Zusanli) em camundongos

Abstract

LASER acupuncture (LA) is a health care technique in which Low-intensity LASER is yielded in acupuncture points to produce a biological action in order to induce biochemical, bioenergetic and bioelectrical effects in cells. ST36 (Zusanli) is acupuncture point commonly used for treating various pathological changes, such as inflammation, acute pain and gastrointestinal disorders. Objective: To investigate the possible mechanisms of action of LA in ST36 (Zusanli) acupoint on the anti-inflammatory and antinociceptive activities in acute and chronic models in mice. Method: Animals were treated with LA (830 nm, 4 J/cm2, 30 mW) in ST36 acupuncture point. The experiment used to assess the anti-inflammatory action of LA was the model of acute inflammation induced by carrageenan in the rat paw edema model, which was evaluated by micrometry and infrared thermography. After that, the levels of reactive oxygen species (ROS), lipid hydroperoxide (LOOH) and reduced glutathione (GSH) were quantified. In another set of experiments, paw edema was induced by bradykinin (BK), histamine (HIST) and prostaglandin E2 (PGE2). Nociception was evaluated by chemical induction (glutamate, capsaicin and cinnamaldehyde). It was also evaluated the mechanical allodynia in models of neuropathic pain, applying the Partial Sciatic Nerve Ligation model (PSNL) and chronic inflammation by means of Complete Freund's Adjuvant (CFA). Muscarinic, adrenergic α1 and α2 and adenosinergic systems were assessed after treatment of LA in ST36 acupoint with pre-treatment using atropine, prazosin, yombina and caffeine, found in glutamate model. Results: LA in acupoint ST36 significantly inhibited edema formation during 4 h after carrageenan injection in the paw and reduced the temperature by 10%. Moreover, LA also reduced the levels of ROS (55%) and LOOH (50%), however, did not alter levels of GSH. The application of LA reduced paw edema induced by BK (30 min 6%, 60 min: 7%), HIST (30 min: 11%) and PGE2 (90 min: 10%, 120 min: 16%). LA in ST36 acupoint reduced the nociception induced by glutamate, capsaicin and cinnamaldehyde with inhibition of 44%, 53% and 80%, respectively. A single application inhibited the response of mechanical allodynia in models of PSNL and CFA. The long-term treatment with LA, once a day, also reduced mechanical allodynia for eight days of application. Muscarinic, adrenergic α2 and adenosinergic systems appear to be linked to the effect of stimulation of the ST36 acupoint in LA, since reducing the nociceptive behavior was reversed by antagonists used when checked in glutamate model. However, the analgesic effect of LA was not influenced by antagonist α1 adrenergic receptor. Conclusion: The results suggest an important antinociceptive and anti-inflammatory activity of LA in ST36 acupoint in experimental models of nociception and acute and chronic inflammation in mice by means of muscarinic systems, adrenergic α2 and adenosinergic.