Influence Of Gender And Obesity On Analgesic Modulation Of Tramadol In Rats

Objective: The objective of this study was to investigate the influence of gender and obesity on analgesic modulation of tramadol in Wistar rats.Methods: This study was carried out in two sets of experiments. In Set I experiment - 48 rats (body weight ≤150 g), 24 each male and female rats were randomly divided into two groups (n=6/group) (Group I - Control; 0.9% NaCl; 1 ml/kg/day i.p. and Group II - Tramadol 10 mg/kg/day i.p.) for each nociception model - plantar test and acetic acid-induced writhing test. The treatment duration was of 5 days. On the last day of treatment (i.e., on the 5th day), paw withdrawal latency (PWL) was assessed using plantar test, and writhing movements were observed following administration of 0.8% acetic acid; 10 ml/kg i.p. Set II experiment was repeated like Set I experiment among rest 48 high-fat diet-fed rats (body weight ≥300 g).Results: For both males and females, PWL was significantly decreased (p<0.05) in obese control groups compared to lean control groups. A number of writhing movements were significantly increased (p<0.01 for males and p<0.001 for females) in obese control groups compared to lean control groups. In tramadol-treated obese rats, PWL was significantly decreased (p<0.01 for males and p<0.05 for females), and number of writhing movements were significantly increased (p<0.01 for both males and females) in comparison with the tramadol-treated lean rats.Conclusion: The present study revealed that obese female rats experience more pain sensation to noxious stimuli compared to lean male rats and also the analgesic effect of tramadol is more pronounced in lean male rats compared to obese female rats.