OBJECTIVE: In pain management, alternative medications are necessary due to the development of tolerance to traditional opioid analgesics. Literature data suggest that N-methyl-D-aspartate (NMDA) receptor antagonizing drugs can induce antinociception, and can reduce the opioid requirement. Ketamine is a non-competitive NMDA receptor antagonist drug and has well-known antinociceptive properties. The drug acts not only on NMDA receptors but also has effects on the monoaminergic system and non-NMDA glutamatergic receptors which have vital roles in the regulation of pain. This study was conducted to investigate the serotonergic and glutamatergic involvement in low-dose ketamine (20 mg/kg) analgesia in mice. METHOD: The effects of serotonin were suppressed with two different ways; either the serotonin was depleted with p-chlorophenylalanine (pCPA, 150 mg/kg/d; 4 days) or the serotonin receptors were blocked with methiothepin (0.1 mg/kg), and α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptors were antagonized with GYKI-52466 (20 mg/kg). Fluoxetine (20 mg/kg; 7 days) was used to increase the serotoninergic activity. We used a hotplate (HP) test to measure pain reaction latencies. Furthermore, we tested sustained analgesic effects of ketamine for six consecutive times (1-hour break between each test). RESULTS: In our experiment, ketamine treatment increased pain reaction latencies, yet it failed to increase the latencies when combined with antiserotonergic drugs, e.g. pCPA and methiothepin. The latencies were increased with AMPA receptor blockade, yet ketamine did not increase the analgesic effect of the AMPA receptor antagonist, i.e. GYKI-52466. In consecutive tests, ketamine was effective for 5 h, and the peak effect was seen at the 3rd-hour test. CONCLUSION: Our data suggest that the activity of the serotonergic system and AMPA receptors are necessary for ketamine to produce antinociceptive effects. In pain management, ketamine can offer an alternative option to traditional analgesics and may be useful to reduce opioid tolerance.

Background: Colistin is increasingly being used as a last-line treatment option for multidrug-resistant Gram-negative infections; however, its clinical use remains limited due to its nephrotoxic side effects. This study investigated the potential nephroprotective effects of ethyl pyruvate (EP) and rutin hydrate (RH), alone and in combination, against colistin-induced renal damage. Methods: Forty-nine adult male Wistar albino rats were allocated into seven groups, and all agents were administered intraperitoneally once daily for seven days. On the eighth day, one kidney of each animal was perfused using a Langendorff system to measure perfusion pressure, while samples from the contralateral kidney and blood were used for biochemical, molecular, and histopathological analyses. Results: In the colistin group, urea, creatinine, total oxidant status, and perfusion pressure were significantly higher than in the control, EP, and RH groups (p < 0.05). Oxidative stress index, tissue MDA, KIM-1, caspase-3, and PUMA levels were also markedly increased. All of these parameters decreased in the treatment groups, with the lowest values for most parameters in the group receiving both EP and RH, which also showed the best-preserved renal architecture. Conclusions: These findings suggest that EP and RH may be promising adjuvant agents against colistin-induced nephrotoxicity. Combined EP and RH co-treatment showed numerically greater protection across most assessed parameters, although an overall advantage over single-agent co-treatment was not statistically established.

This study investigated the effects of different doses of ranolazine in a middle cerebral artery occlusion/reperfusion (MCAO-I/R) model by evaluating histopathological changes and serum Sirtuin 1 (SIRT1), Apela peptide (APELA), and Apelin-13 (APL13) levels. A total of 47 male Sprague Dawley rats (250 ± 20 g) were randomly assigned to five groups: Sham (n = 7), MCAO (n = 10), MCAO+RAN10 (n = 10), MCAO+RAN30 (n = 10), and MCAO+RAN50 (n = 10). MCAO-I/R was induced by transient filament occlusion of the right middle cerebral artery for 90 min followed by reperfusion. Ranolazine was administered intraperitoneally once daily for 21 days in the treatment groups. Serum SIRT1, APELA, and APL13 levels were measured using enzyme-linked immunosorbent assay (ELISA), and brain tissues were evaluated histopathologically for neuronal degeneration and apoptotic cell counts. Histopathological analysis revealed significant neuronal degeneration and increased apoptosis in the MCAO group compared with the Sham group. Ranolazine treatment did not demonstrate significant histopathological improvement compared with the untreated MCAO group. Among the treatment groups, the MCAO+RAN50 group showed higher apoptotic cell counts and lower serum biomarker levels than the other ranolazine-treated groups. Serum SIRT1, APELA, and APL13 levels were lowest in the MCAO+RAN50 group, with selected pairwise differences reaching statistical significance. Under the present experimental conditions, clear evidence of neuroprotection could not be demonstrated. None of the ranolazine-treated groups showed significant histopathological improvement compared with the untreated MCAO group. These findings indicate that higher-dose ranolazine was not associated with neuroprotection under the conditions of this study. However, given the limited sample size, absence of infarct volume analysis, lack of neurological functional assessment, and absence of tissue-level molecular validation, further studies are required to clarify the biological significance and potential clinical relevance of the observed biomarker changes.