Background: The aim of the present study was to investigate the protective properties of melatonin (MT)
against oxidative stress, mitochondrial dysfunction, and apoptosis induced by tramadol-reproductive toxicity
in male rats.
Methods: The rats were divided into the 7 groups of control, melatonin (1.5 mg/kg), tramadol (50 mg/kg), and
melatonin (1, 1.5 and 2.5 mg/kg) administered 30 minutes before tramadol and vitamin C group (100 mg/kg).
All injections were performed intraperitoneally. After administration for 3 consecutive weeks, the animals were
killed and testis tissues were used for assessment of oxidative stress markers including lipid peroxidation
(LPO), glutathione (GSH) content and protein carbonyl (PrC), and sperm analysis. Mitochondria were isolated
from rat’s testis using differential centrifugation technique and were studied in terms of mitochondrial
viability, mitochondrial membrane potential (MMP), and mitochondrial swelling. The other part of the tissue
sample was placed in RNA protector solution for assessment of Bax and Bcl-2 gene expression through realtime polymerase chain reaction (real-time PCR) assay.
Findings: Tramadol caused a significant decline in epidermal sperm count, motility, and morphology, as well
as a significant decrease in GSH level and mitochondrial function, and a significant evaluation of LPO, PrC,
MMP, and mitochondrial swelling. In addition, tramadol induced a significant decrease in Bcl-2 gene
expression, and increase in Bax gene expression. However, pretreatment of rats with MT improved sperm
analysis, and testicular antioxidative status, and mitochondrial function. Furthermore, MT pretreatment
regulated testicular Bcl-2 and Bax expressions.
Conclusion: Considering the protective effects of MT against reproductive toxicity induced by tramadol, this
compound can be used as a possible agent for the prevention and treatment of tramadol-induced reproductive