Potent Ameliorative Effects of Rosmarinic Acid on Tramadol-Induced Neurotoxicity in the Brain and Hippocampus; by Suppressing Oxidative stress, Apoptosis, ER stress, and Regulating Cognitive Functions

Tramadol (TRM) is a synthetic opioid analgesic that acts on the central nervous system and is used to treat moderate or severe pain. However, the incidence of its abuse is increasing. Rosmarinic acid (RA) is a natural flavonoid known for its antioxidant, anti-inflammatory, and neuroprotective properties. In this study, we determined the ameliorative effects of RA against TRM-induced neurotoxicity. Thirty five rats were divided into 5 groups; control, RA, TRM, TRM + RA25 and TRM + RA50. TRM 50 mg/kg was administered intraperitoneally, and RA 25 and 50 mg/kg doses were administered by oral gavage for 14 days. Water Maze Test (WMT) was performed to assess cognitive function. Oxidative stress, inflammation, endoplasmic reticulum (ER) stress, apoptosis damage pathways, glial fibrillary acidic protein (GFAP), and brain-derived neurotrophic factor (BDNF) activities were determined in brain and hippocampus tissues. The structural and functional integrity of the tissues were also analyzed. RA decreased TRM-induced increased oxidative stress, inflammation, ER stress, and apoptotic damage levels. In addition, it improved neuronal survival and activity by bringing BDNF and GFAP activities closer to normal in brain tissue. RA restored the structural properties of brain and hippocampus tissues disrupted by tramadol. These findings were also demonstrated using WMT, which improved the arrival time to the quadrant in which the platform was located and the time spent in the quadrant. RA reduces TRM-induced neurotoxicity by reducing inflammation, oxidative stress, ER stress, and apoptotic damage and increases neuronal survival and activity.