Participation Of Opioid System Research Articles

Antinociceptive and anti-inflammatory activities of Philodendron bipinnatifidum Schott ex Endl (Araceae)

Ethnopharmacological relevancePopular medicine use stems of Philodendron bipinnatifidum (Araceae) in inflammation cases, such as in erysipelas, as well as orchitis and rheumatism treatment. The present study, conducted for the first time in literature, investigate the antinociceptive and anti-inflammatory activities of P. bipinnatifidum stems ethyl acetate extract (EPB). Materials and methodsGC/MS and HPLC analysis were performed for EPB extract. We used EPB at 250, 375 and 500 mg/kg (oral route, p.o.) in male Swiss mice. The antinociceptive activity of the plant extract assessed by acetic acid induced writhing and formalin tests. To investigate the possible participation of opioid system in EPB-mediated effects, we previously administered naloxone to the mice. Anti-inflammatory activity was evaluated using carrageenan-induced paw oedema. The open-field test aimed to investigate the possible EPB effects on the locomotor and exploratory activities. To assess the protective role of EPB on carrageenan-induced oxidative stress, the levels of NPSH, TBARS, as well as SOD and CAT activities were evaluated in blood and paw tissue. The acute toxicity of the EPB was investigated using OECD 423 guideline. ResultsThe EPB chemical analysis by GC/MS and HPLC revealed the presence of flavonoids (luteolin and quercetin) and phytosterols (β-sitosterol and stigmasterol). The oral treatment with the EPB inhibited mice abdominal writhings (P < 0.01) at 375 and 500 mg/kg, and reduced the formalin effect at the first-phase (500 mg/kg, P < 0.05) and also at the second-phase (500 mg/kg, P < 0.001) of the test. EPB (375 and 500 mg/kg) did not alter spontaneous locomotion in open field test, however the number of fecal bolus was significantly lower for the EPB group at 500 mg/kg when compared to the vehicle group (P < 0.05). The pretreatment with naloxone caused significant inhibition of antinociceptive activity induced by EPB in the formalin test, revealing the possible involvement of opioid receptors. EPB extract administered at 500 mg/kg (p.o.) prevented carrageenan-induced paw oedema (P < 0.05 and 0.01) until 6 h after carragenan injection. Evaluation of TBARS and NPSH levels, SOD and CAT activities in the blood and paw tissue of animals submitted to the carrageenan assay suggested that the anti-inflammatory effect of EPB may be linked to oxidative stress inhibition. The acute administration of the EPB (2000 mg/kg, p.o.) caused no mortality, demonstrating low toxicity. ConclusionsThe extract of P. bipinnatifidum displays antinociceptive and anti-inflammatory activities, causing no toxicological effects. The pharmacological activity of this vegetal species may be related to the presence of flavonoids and phytosterols. Our results support the ethnomedical use of this vegetal species as analgesic and anti-inflammatory agent.

The leguminous lectin of Lonchocarpus araripensis promotes antinociception via mechanisms that include neuronal inhibition of Na(+) currents.

Sodium channels are highly expressed in nociceptive sensory neurons during hypernociceptive conditions. Based on the presence of a glycosidic portion in the sodium channel β subunit associated to the antinociceptive effect of leguminous lectins via lectin domain, this study investigated the antinociceptive activity of the lectin isolated fromLonchocarpus araripensisseeds (LAL) in micebehavioralmodels andin NaV current in the nociceptor of rat dorsal root ganglion (DRG). LAL antinociceptive activity and the participation of opioid system, lectin domain and sodium channels were evaluated in Swiss mice models of nociception (formalin, capsaicin, hot plate, tail flick, von Frey) and in primary cultures of Wistar rats neurons of DRG (patch clamp). LAL presented inhibitory effects in the nociception induced by chemical and mechanical, but not by thermal stimuli and reduced total Na(+) current. LAL activity was inhibited by the lectin association with its binding sugar N-acethyl-glucosamine. LAL inhibits peripheral hypernociception by mechanisms that involve the lectin domain, inflammatory mediators and Na(+) channels. The innovative inhibitory action of leguminous lectins on NaV current brings new insights for the investigation of sodium channels role in nociception.

Evaluation of antinociceptive activity of ethanol extract of bark of Polyalthia longifolia

Ethnopharmacological relevancePolyalthia longifolia var. pendula is a very popular herb in Bangladesh due to its traditional uses in treatment of rheumatism, bone fracture and gastric ulcer. The present study was conducted to investigate the antinociceptive activity of ethanol extract of P. longifolia (EEPL) bark. Materials and methodsHot plate and tail immersion tests, acetic acid-induced writhing test, glutamate and formalin-induced paw licking tests in mice were employed in this study. In all the experiments EEPL was administered orally at the doses of 50, 100 and 200mg/kg body weight. To investigate the possible participation of opioid system in EEPL-mediated effects, naloxone was used to antagonize the action. ResultsEEPL showed a significant antinociceptive activity against both heat and chemical-induced nociception. The effects were dose-dependent and significant at the doses of 100 and 200mg/kg of EEPL. Besides, pretreatment with naloxone caused significant inhibition of the antinociceptive activity induced by EEPL, revealing the possible involvement of the opioid receptors. ConclusionThese results indicate the antinociceptive activity of the bark of P. longifolia and support the ethnomedical use of this plant in treatment of different painful conditions.

Participation of the opioid system in cannabinoid-induced antinociception and emotional-like responses

Several anatomical, biochemical and pharmacological evidence support the existence of bidirectional interactions between cannabinoid and opioid systems. The present review is focused on the participation of the endogenous opioid system in the antinociceptive and emotional-like responses induced by cannabinoids, and the development of tolerance to cannabinoid pharmacological effects. Cannabinoid and opioid agonists produce antinociception by acting on similar structures within the central nervous system, and a peripheral mechanism has been also proposed for both compounds. Pharmacological studies have suggested that the endogenous opioid system could be involved in cannabinoid antinociception and the development of cannabinoid tolerance. Recent studies using knockout mice have also demonstrated the role of the opioid system in cannabinoid antinociception and tolerance, although some discrepancies with the previous pharmacological results have been reported when using knockout mice. On the other hand, cannabinoid administration can induce anxiolytic-like responses that are mediated at least in part by an endogenous opioid activity on μ- and δ-opioid receptors.