Nitric Oxide and Opioids Involvement in Isobolographic Nsaids Antinociception.

Different NSAIDs are used as antinociceptive in various analgesic assays, among which should be mentioned: ibuprofen, ketorolac , ketoprofen, meloxicam , paracetamol and others. It has been shown that NSAIDs possess antinociceptive activity by blocking cyclooxygenase enzymes (COXs). The present study was designed to evaluate the possible involvement of the nitridergic pathway due to L-NAME and the opioidergic route by NTX in the antinoception induced by NSAIDs using a murine pain model the tail flick test in an automatic tail flick algesiometer. The antinociception was evaluated by means of isobolographic analysis. The interaction between the combination of NSAIDs, via i.p., on basis of their ED25, demonstrated that the coadministration of the drugs were synergistic with the exception of the lack of effect in combination of meloxicam with ibuprofen and with ketorolac, since the result was additive. These data validate that the NSAIDs administered alone or in combinations produce antinociception in which other mechanisms of action must be added to the simple inhibition of COXs. In addition, the pretreatment of the mice with L-NAME and NTX does not change previous isobolographic parameters of the mixture of NSAIDs.

Non-steroidal Anti-inflammatory Drugs in Tonic, Phasic and Inflammatory Mouse Models.

The principal mechanism of action of non-steroidal anti-inflammatory drugs (NSAIDs) is the inhibition of ciclooxigenases. In this study was evaluated if NSAIDs could induce antinociceptive differences according to the type of murine pain model. Male mice were injected intraperitoneally with meloxicam, diclofenac, piroxicam, metamizol, ibuprofen, naproxen and paracetamol in the writhing, tail flick and formalin orofacial tests and dose-response were analyzed to obtain the ED50 of each drugs. Administration of NSAIDs produced in a dose-dependent antinociception with different potency in the tests. The relative potency of NSAIDs among the tests shows a value of 5.53 in the orofacial formalin test in phase I and 6.34 in phase II between meloxicam and paracetamol; of 7.60 in the writhing test between meloxicam and paracetamol and of 8.46 in the tail flick test between ibuprofen and paracetamol. If the comparison is made for each NSAID in the different tests, the minimum value was 0.01 for between writhing and phase II of the orofacial formalin. Meanwhile, the highest power ratio was 11.71 for diclofenac between writhing and tail flick tests. In conclusion, the results suggests that intraperitoneal NSAIDs administration induce antinociceptive activity depending on the type of pain. The results support that NSAIDs administration, induce a wide variety of antinociceptive effect, depending on the type of pain. This suggest the participation of different mechanisms of action that can be added to the simple inhibition of COXs controlled by NSAIDs.

Synergism between gabapentin-tramadol in experimental diabetic neuropathic pain.

Neuropathic pain is associated with several conditions such as surgery, cancer, and diabetes and can be induced experimentally. Among the drugs used as monotherapy are gabapentin and tramadol. The purpose of this study was to evaluate the coadministration of gabapentin and tramadol, by isobolographic analysis, in three different algesiometric assays in experimental diabetic neuropathic pain induced by streptozocin in mice. In all the behavioral tests, gabapentin or tramadol produced a dose-dependent antinociception and their coadministration resulted in a positive interaction. This effect can be explained by principles of multimodal analgesia, whereby the different mechanisms of action of each drug contribute to the combined effect in a supra-additive manner. The findings of the present study suggest that the combination of gabapentin and tramadol could be a useful strategy for the treatment of pain induced by diabetic neuropathy.

Antinociception induced by rosuvastatin in murine neuropathic pain.

BACKGROUND: Neuropathic pain, and subsequent hypernociception, can be induced in mice by paclitaxel (PTX) administration and partial sciatic nerve ligation (PSNL). Its pharmacotherapy has been a clinical challenge, due to a lack of effective treatment. In two models of mouse neuropathic pain (PTX and PSNL) the antinociception induced by rosuvastatin and the participation of proinflammatory biomarkers, interleukin (IL)- 1ß, TBARS and glutathione were evaluated. METHODS: A dose-response curve for rosuvastatin ip was obtained on cold plate, hot plate and Von Frey assays. Changes on spinal cord levels of IL-1ß, glutathione and lipid peroxidation were measured at 7 and 14days in PTX and PSNL murine models. RESULTS: PTX or PSNL were able to induce in mice peripheral neuropathy with hypernociception, either to 7 and 14days. Rosuvastatin induced a dose dependent antinociception in hot plate, cold plate and Von Frey assays. The increased levels of IL-1ß or TBARS induced by pretreatment with PTX or PSNL were reduced by rosuvastatin. The reduction of spinal cord glutathione, by PTX or PSNL, expressed as the ratio GSH/GSSG, were increased significantly in animals pretreated with rosuvastatin. The anti-inflammatory properties of statins could underlie their beneficial effects on neuropathic pain by reduction of proinflammatory biomarkers and activation of glia. CONCLUSION: The findings of this study suggest a potential usefulness of rosuvastatin in the treatment of neuropathic pain.