Tramadol induces alterations in the cognitive function and histoarchitectural features of the hippocampal formation in adult Wistar rats.

Abstract

BACKGROUND AND AIM: Tramadol abuse has a substantial risk of altering the histoarchitecture and causing cognitive decline. Therefore, this study investigated the effects of tramadol on cognitive function and histopathological changes in the structures of the hippocampal formation. METHODOLOGY: Twelve apparently healthy Wistar rats (120-150g) were used for this study. They were divided into two groups with six (n=6) rats in each group. The control group was given 2ml/kg of distilled water while 50 mg/kg of tramadol was given to group 2 orally for 21 days. The Morris Water Maze (MWM) was utilized to assess spatial learning and memory over the last six days of the experiment. The rats were euthanized and brains harvested, fixed in 10% formol saline, and processed routinely using haematoxylin & eosin (H&E) for general histoarchitecture.   RESULTS: The result of MWM showed a prolonged time taken and longer distance covered to locate the escape platform in the acquisition phase while the probe test showed less time spent in the target quadrant in which the platform was previously located in the tramadol-treated group. Histologically, there were several neuronal degenerative changes presenting as pyknotic nuclei, dark neurons, vacuolations, congested blood vessels, karyorrhexis, necrotic cells, and infiltration of cells in the various layers of the structures of the hippocampal formation. CONCLUSION: Findings from this study revealed changes in spatial learning and memory, and hippocampal formation histopathology.