Avaliação das atividades antinociceptiva e anti-inflamatória do extrato hidroetanólico de partes aéreas de Portulaca pilosa L. (Portulacaceae)

Abstract

This study investigated the acute oral toxicity, the antinociceptive effect in chemical and thermal nociception models as such as the anti-inflammatory activity in carrageenan and croton oil models of the hydroethanolic extract from aerial parts of Portulaca pilosa (HEEPp). Also identified some possible mechanism involved in antinociception of the extract as such as the effects of HEEPp on central nervous system of rats. In the oral acute toxicity test, the treatment with HEEPp ( 2000 mg/kg) caused no deaths. In the acetic acid-induced writhing test, the HEEPp (100, 200, 400 and 600 mg/kg) administered by oral route (p.o.) significantly reduced the number of contortions acetic acid-induced in 18.18, 33.25, 47.27, 65.81 e 73.94%, respectively. In the hot plate test, the treatment with HEEPp (200, 400 e 600 mg/kg, p.o.) did not alter the latency to the thermal stimuli of 50 ± 0,5 ºC. In the formalin test, the treatment with HEEPp (200, 400 e 600 mg/kg, p.o.) significantly reduced the licking-time in neurogenic phase (first phase) in 38.79, 60.61 and 75.18 %, and inflammatory phase (second phase) in 49.23, 53.03 e 87.53 %, respectively. The previous naloxone administration, significantly reversed the effect of HEEPp (600 mg/kg, p.o.) in both phases of the formalin test. The pre-treatment with L-NAME and methylene blue significantly reversed the effect of HEEPp (600 mg/kg, p.o.) in both phases of the formalin test. The pre-treatment with glibenclamide also significantly reversed the effect of HEEPp (600 mg/kg, p.o.) in both phases of the formalin test. HEEPp (600 mg/kg, p.o.) did not affect the locomotor activity of rats in the open field test. In the carrageenan-induced paw edema and croton-induced ear edema, the HEEPp (400 and 600 mg/kg, p.o.) did not inhibit significantly the edema formation in both the tests. The results of this study showed that HEEPp, when administered by oral route, presented low toxicity and its antinociceptive actuation observed in neurogenic phase involves peripherals interaction with opioids receptors and activation of the in the NO/GCs/GMPc/ KATP pathway. Already the antinociceptive activity observed in the inflammatory phase does not seem to depend of the inhibition on via phospholipase A2/cyclooxygenases, but interaction with peripheral opioid receptors and the NO/sGC /cGMP/ KATP pathway.