Antinociceptive activity of Riparin II from Aniba riparia: Further elucidation of the possible mechanisms.

Riparin II (RipII) has an anti-inflammatory activity potentially due its ability to decrease TNF-α and IL-1ß production and its histamine antagonism. The objective of this study was to evaluate the role of RipII in the pain process and the possible antinociceptive mechanisms involved, using classic models of nociception. Male Swiss mice were used in the assays. Determinate the acute toxicity according to the OECD 425 test guideline. The models used were the acetic acid-, formalin-, hot plate and glutamate-induced nociception. For evaluation of antinociceptive effect, the involvement of TRPV1, TRPA1, TRPM8, ASICS, Bradykinin, PKC and PKA were performed using the paw licking using agonists. The acute toxicity study did not detect any clinical signs or changes in behavior or mortality. RipII, administered orally (25 and 50 mg/kg) caused a reduction of nociception induced by acetic acid, formalin (on the second phase) and glutamate. In the investigation of antinociceptive mechanism, we used capsaicin (2.2 µg/paw), cinnamaldehyde (10 nmol/paw), menthol (1.2 µmol/paw), ASICS (2% acetic acid, pH 1.98) and bradykinin (10 µg/paw). The results showed that TRPV1, TRPA1, TRPM8, ASICS and bradykinin play a role in the antinociceptive effect of RipII. The results also showed that PKA is involved too. These data demonstrate that RipII has a low or not toxicity and produced an important antinociceptive effect through mechanisms that probably involve an interaction, at least in part, TRPV1, TRPA1, TRPM8, ASICS, bradykinin and PKA participate in the RipII's antinociceptive effect.

Involvement of the nitric oxide/cyclic guanylate monophosphate pathway in the pilocarpine-induced seizure model in mice.

The present study was designed to investigate the involvement of the nitric oxide (NO)/cyclic guanylate monophosphate pathway in pilocarpine-induced seizures in mice. Male Swiss mice (26-32 g) were used as the in vivo model. The following pharmacological tools were utilized: the non-selective NO synthase (NOS) inhibitor L-NAME (10 mg/kg, i.p.), a preferential inducible NOS (iNOS) inhibitor aminoguanidine (25 mg/kg, i.p.), a highly specific iNOS inhibitor 1400W (2.5 mg/kg, i.p.), the NO donor L-arginine (150 mg/kg, i.p.), and the soluble guanylyl cyclase inhibitor ODQ (10 mg/kg, i.p.). The animals were divided into groups (n = 8) and pretreated for 30 min before receiving pilocarpine (400 mg/kg, i.p.), while the control group received only pilocarpine. They were observed for 60 min to measure initial seizure latency, latency till death, and mortality. An administration of L-NAME or ODQ delayed the onset of initial seizure, increased latency till death, and produced a 25% survival rate. Aminoguanidine increased the initial seizure and latency until death, and administration of 1400W did not have an effect. Incremental increases of NO by L-arginine were capable of decreasing the seizure and death latency. These results support the idea that the constitutive NOS, probably neuronal NOS, followed by soluble guanylyl cyclase activation is involved in the convulsive responses caused by pilocarpine administration.

Gastroprotection of (-)-alpha-bisabolol on acute gastric mucosal lesions in mice: the possible involved pharmacological mechanisms.

(-)-Alpha-Bisabolol is an unsaturated, optically active sesquiterpene alcohol obtained by the direct distillation essential oil from plants such as Vanillosmopsis erythropappa and Matricaria chamomilla. (-)-Alpha-Bisabolol has generated considerable economic interest, since it possesses a delicate floral odor and has been shown to have anti-septic and anti-inflammatory activity. The aim of this work was to evaluate the gastroprotective action of (-)-alpha-bisabolol on ethanol and indomethacin-induced ulcer models in mice, and further investigate the pharmacological mechanisms involved in this action. The oral administration of (-)-alpha-bisabolol 100 and 200 mg/kg was able to protect the gastric mucosa from ethanol (0.2 mL/animal p.o.) and indomethacin-induced ulcer (20 mg/kg p.o.). Administration of L-NAME (10 mg/kg i.p.), glibenclamide (10 mg/kg i.p.) or indomethacin (10 mg/kg p.o.) was not able to revert the gastroprotection promoted by (-)-alpha-bisabolol 200 mg/kg on the ethanol-induced ulcer. Dosage of gastric reduced glutathione (GSH) levels showed that ethanol and indomethacin reduced the content of non-protein sulfhydryl (NP-SH) groups, while (-)-alpha-bisabolol significantly decreased the reduction of these levels on ulcer-induced mice, but not in mice without ulcer. In conclusion, gastroprotective effect on ethanol and indomethacin-induced ulcer promoted by (-)-alpha-bisabolol may be associated with an increase of gastric sulfydryl groups bioavailability leading to a reduction of gastric oxidative injury induced by ethanol and indomethacin.