Comprehensive Evaluation of Malnutrition Effect on Pain Threshold in Albino Rats

This present study was aimed at exploring the effect of protein malnutrition and micronutrient deficiencies on pain threshold in the rat. Thirty adult male rats used were divided into five groups of six rats each, (1) normal diet ND, (2) low-protein diet LP, (3) low protein minerals and vitamin diet LPMV, (4) low protein and vitamin diet LPV and (5) low protein and mineral diet LPM. The normal diet fed rats served as the control group. Both the control and the experimental groups were fed accordingly for a total period of six weeks. Hot plate and tail-flick (thermal) and formalin (chemical) tests were applied to assess the possible effect of protein and micronutrient deficiencies on the sensitivity of the rats to the stimuli at the end of the second, fourth and sixth week. Pain threshold was markedly reduced in the malnourished rats when compared to the control group fed with the standard diet. Latencies significantly decreased in the groups LP, LPMV, LPV and LPM over the 0-90 min observation period in hot plate test and 48-55°C for tail immersion test; p<0.001. Also, significant decrease in latencies was observed in LPMV, LPV and LPM when compared with the LP group; p<0.05. In Formalin test, LP, LPMV, LPV and LPM groups in both early and late phases showed a more prolonged time with paw licking when compared to the control group; p<0.001. Similarly, when LPV and LPM were compared with the LP group, a significant increase in the licking time was observed; p<0.05, with significant level of LPMV being the highest; p<0.001. These results demonstrate that both protein malnutrition and micronutrients (vitamins and minerals) deficiencies are capable of overt hypersensitivity to acute and chronic pain.