Obesity attenuates formalin-induced tonic pain in British Angora rabbits

Obesity is known to alter various physiological parameters including the pain sensitivity. There are conflicting reports on the pain sensitivity in obesity. In this context, the present study was aimed to investigate the tonic pain response in obese rabbit model. To achieve this aim, two groups of adult male British Angora rabbits were used. One of the groups was fed with standard rabbit chow and served as control. The other group was fed high fat diet (HFD) for 10 weeks to produce obesity. The standard formalin test was performed at the start and after 10 weeks of dietary regimen in both the groups. Timed behavioral responses (limping, elevation of paw, licking, biting, grooming etc.) were categorized and quantified with the help of standard pain rating scale. The total average pain rating score decreased significantly from 2.01 +/- 0.02 to 1.47 +/- 0.08 (P < 0.05) in HFD group after 10 weeks of dietary regimen, whereas there was no change in the control group. A significant negative correlation was observed between body weight and pain rating score in HFD group of rabbits (P < 0.05, r = -0.62). Results suggest that obesity attenuates the tonic pain responses induced by formalin in British Angora rabbits.