The role of adenosine A1 receptor in the peripheral tramadol's effect in the temporomandibular joint of rats

Immunomodulation by tramadol combined with acetaminophen or dexketoprofen: In vivo animal study

Among other functions, macrophages remove foreign particles, including medications, from the circulation, making them an important target for immunomodulatory molecules. Currently, growing evidence suggests that analgesics affect the activity of immune cells not directly related to pain, and thus may induce unwanted immunosuppression in patients at risk. However, the immunomodulatory effects resulting from macrophage targeting by these drugs are understudied. Therefore, the current study investigated the immune effects induced in healthy mice by repeated administration of tramadol alone or in combination with acetaminophen or dexketoprofen. We observed that drug administration decreased the percentage of infiltrating macrophages in favor of resident macrophages in peritoneal exudates. While all drugs reduced the number of infiltrating macrophages that phagocytosed sheep red blood cells (SRBC), their administration increased the effectiveness of phagocytosis, and treatment with acetaminophen with or without tramadol elevated the expression of MHC class II by Mac3+ macrophages. Interestingly, SRBC-pulsed macrophages from mice treated with tramadol combined with acetaminophen potently activated SRBC-specific B cells in humoral response, and administration of these drugs to recipients of contact hypersensitivity effector cells augmented the resulting cellular immune response. In addition, tramadol administered alone or with dexketoprofen enhanced the spontaneous release of pro-inflammatory cytokines by macrophages. Our current research findings demonstrate that tramadol therapy in combination with acetaminophen or dexketoprofen has a relatively low risk of causing immunosuppressive side effect because the drugs slightly reduce the inflammatory reaction of macrophages but do not impair their ability to activate the adaptive immune responses.

Effect of nitric oxide-cyclic GMP-K+ channel pathway blockers, naloxone and metformin, on the antinociception induced by the diuretic pamabrom

Pamabrom is a diuretic that is effective in treating premenstrual syndrome and primary dysmenorrhea. The aim of this study was to examine the effect of metformin and modulators of the opioid receptor-nitric oxide (NO)-cyclic guanosine monophosphate (cGMP)-K⁺ channel pathway on the local antinociception induced by pamabrom. The rat paw 1% formalin test was used to assess the effects. Rats were treated with local administration of pamabrom (200-800 µg/paw) or indomethacin (200-800 µg/paw). The antinociception of pamabrom or indomethacin was evaluated with and without the local pretreatment of the blockers. Local administration of pamabrom and indomethacin produced dose-dependent antinociception during the second phase of the test. Local pretreatment of the paws with naloxone (50 µg/paw), l-nitro-arginine methyl ester (10-100 µg/paw), or 1H-(1,2,4)-oxadiazolo[4,2-a]quinoxalin-1-one (10-100 µg/paw) reverted the antinociception induced by local pamabrom, but not of indomethacin. Similarly, the K⁺ channel blockers glibenclamide, glipizide, 4-aminopyridine, tetraethylammonium, charybdotoxin, or apamin reverted the pamabrom-induced antinociception, but not of indomethacin. Metformin significantly blocked the antinociception of pamabrom and indomethacin. Our data suggest that pamabrom could activate the opioid receptor-NO-cGMP-K⁺ channel pathway to produce its peripheral antinociception in the formalin test. Likewise, a biguanide-dependent mechanism could be activated by pamabrom and indomethacin to generate antinociception.