Supplementation of Carvacrol Attenuates Hippocampal Tumor Necrosis Factor-Alpha Level, Oxidative Stress, and Learning and Memory Dysfunction in Lipopolysaccharide-Exposed Rats

Abstract

Background: Carvacrol is a natural phenolic monoterpene with anti-inflammatory and antioxidant bioactivities. Neuroinflammatory and oxidative stress responses play a crucial role in the pathogenesis of Alzheimer's disease. The present study examined the effect of carvacrol on brain tumor necrosis factor-alpha (TNF-alpha) level and oxidative stress as well as spatial learning and memory performances in lipopolysaccharide (LPS)-exposed rats. Materials and Methods: The rats were treated with either carvacrol (25 and 50 mg/kg) or Tween 80 for 2 weeks. Thereafter, LPS (1 mg/kg) or saline was intraperitoneally administered on days 15-19, 2 h before Morris water maze task, and treatments with carvacrol or Tween 80 were performed 30 min prior to behavioral testing. The level of TNF-alpha, lipid peroxidation, and total thiol concentration were measured in the hippocampus and cerebral cortex at the end of the experiment. Results: It was found that LPS-exposed rats exhibited spatial learning and memory dysfunction, which was accompanied by increased TNF-alpha level and lipid peroxidation, and decreased total thiol concentration in the hippocampus and/or cortex. Moreover, treatment with carvacrol at a dose of 25 mg/kg attenuated learning and memory impairments, decreased TNF-alpha and lipid peroxidation level in the hippocampus and cortex, and increased total thiol concentration in the cortex. Conclusion: Carvacrol exerts neuroprotective effects against LPS-induced spatial memory deficits through attenuating hippocampal TNF-alpha level and oxidative stress in rats.