Evaluation of anti-nociceptive and anti-inflammatory activity of low-level laser therapy on temporomandibular joint inflammation in rodents.

The aim of this study was to investigate the analgesic and anti-inflammatory activity of low-level laser therapy (LLLT) on the nociceptive behavioral as well as histomorphological aspects induced by injection of formalin and carrageenan into the rat temporomandibular joint. The 2.5% formalin injection (FRG group) induced behavioral responses characterized by rubbing the orofacial region and flinching the head quickly, which were quantified for 45 min. The pretreatment with systemic administration of diclofenac sodium-DFN group (10 mg/kg i.p.) as well as the irradiation with LLLT infrared (LST group, 780 nm, 70 mW, 30 s, 2.1 J, 52.5 J/cm(2), GaAlAs) significantly reduced the formalin-induced nociceptive responses. The 1% carrageenan injection (CRG group) induced inflammatory responses over the time-course of the study (24 h, and 3 and 7 days) characterized by the presence of intense inflammatory infiltrate rich in neutrophils, scanty areas of liquefactive necrosis and intense interstitial edema, extensive hemorrhagic areas, and enlargement of the joint space on the region. The DFN and LST groups showed an intensity of inflammatory response that was significantly lower than in CRG group over the time-course of the study, especially in the LST group, which showed exuberant granulation tissue with intense vascularization, and deposition of newly formed collagen fibers (3 and 7 days). It was concluded that the LLLT presented an anti-nociceptive and anti-inflammatory response on the inflammation induced in the temporomandibular joint of rodents.

Hyptis pectinata: redox protection and orofacial antinociception.

Hyptis pectinata L. Poit, known as 'sambacaitá', is used in Brazil to treat inflammatory and painful disorders. In this study, the antioxidant and orofacial antinociceptive properties of the aqueous extract of H. pectinata leaves (AEPH) were assessed using in vitro and in vivo models. Thus, AEPH reduced the 2,2-diphenyl-1-picrylhydrazyl radical up to 72.10% with an EC50 of 14.56 µg/ml. It also inhibited 40.80% of the lipoperoxidation induced by 2'-azobis (2-amidinopropane) dihydrochloride in the thiobarbituric acid-reactive substances assay. The orofacial antinociceptive activity was evaluated in mice pre-treated with AEPH (100, 200 and 400 mg/kg, p.o.) and morphine (5 mg/kg, i.p.), which received afterwards formalin- (20 µl, 2% solution, s.c.), glutamate- (40 µl, 25 mM, s.c.) and capsaicin- (20 µl, 2.5 µg, s.c.) to induce orofacial nociception. AEPH at all doses reduced (p < 0.001) the nociceptive response in the first (43-62%) and second (47-80%) phases of the formalin test. Besides, the effect of AEPH (400 mg/kg) was not changed in the presence of naloxone (1.5 mg/kg, i.p.), an opioid antagonist. AEPH significantly inhibited mice face rubbing for capsaicin (23-69%, p < 0.05) and glutamate (48-77%, p < 0.001) at all doses. The findings suggested the AEPH has peripheral and central antinociceptive activities, which are not related to opioid receptors.

Sida cordifolia leaf extract reduces the orofacial nociceptive response in mice.

In this study, we describe the antinociceptive activity of the ethanol extract (EE), chloroform (CF) and methanol (MF) fractions obtained from Sida cordifolia, popularly known in Brazil as "malva branca" or "malva branca sedosa". Leaves of S. cordifolia were used to produce the crude ethanol extract and after CF and MF. Experiments were conducted on Swiss mice using the glutamate and formalin-induced orofacial nociception. In the formalin test, all doses of EE, CF and MF significantly reduced the orofacial nociception in the first (p < 0.001) and second phase (p < 0.001), which was also naloxone-sensitive. In the glutamate-induced nociception test, only CF and MF significantly reduced the orofacial nociceptive behavior with inhibition percentage values of 48.1% (100 mg/kg, CF), 56.1% (200 mg/kg, CF), 66.4% (400 mg/kg, CF), 48.2 (200 mg/kg, MF) and 60.1 (400 mg/kg, MF). Furthermore, treatment of the animals with EE, CF and MF was not able to promote motor activity changes. These data demonstrate that S. cordifolia has a pronounced antinociceptive activity on orofacial nociception. However, pharmacological and chemical studies are necessary in order to characterize the responsible mechanisms for this antinociceptive action and also to identify other bioactive compounds present in S. cordifolia.