PHYSIOLOGICAL RESPONSES OF WISTAR RATS TO EXPERIMENTALLY-INDUCED PAIN DURING THE HARMATTAN SEASON AND THE MODULATORY ROLE OF RESVERATROL

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Department of Medicine

ABSTRACT
This study investigated the influence of harmattan season (November-February) in naïve animals subjected to mechanical, chemical and thermal noxious stimulation and the modulating effect of resveratrol. Animals were grouped into two major groups of 50 males and females respectively. These major groups were subdivided into control, carboxymethyl cellulose (CMC), resveratrol (RSV) groups with 5 animals each. Different sets of animals were subjected separately to mechanical, chemical and thermal noxious stimulation. Dry bulb temperature readings were taken at 06:00 h, 13:00 h and 18:00 h during the course of the study. After determination of pain thresholds for the three different noxious stimuli, animals were sacrificed and serum was collected for biochemical analyses of sodium, potassium and chloride concentration. Determination of malondialdehyde, superoxide dismutase concentration and erythrocyte osmotic fragility were also carried out. The results obtained revealed that responses to mechanical, chemical and thermal noxious stimuli did not show significantly variation between male and female animals even though females had higher pain sensitivity. Mechanical pain threshold was higher in the morning (06:00 h) and lowest in the evening (18:00 h). Thermal pain threshold was positively correlated (p < 0.05) with time. Resveratrol showed no significant analgesic activity in all the experimentally induced pain paradigms, but CMC groups had significantly lower thresholds when compared to other groups. Sodium ion concentration was highest in animals exposed to mechanical noxious stimulation and lowest in animals exposed to thermal noxious stimulation. Sodium and potassium ion concentrations was significantly higher in male than female animals. Percentage haemolysis of erythrocyte was significantly higher (p < 0.05) in animals subjected to mechanical and chemical noxious stimulation when compared to animals subjected to thermal noxious stimulation. This results were further corroborated by increased viii malondialdehyde concentration and superoxide dismutase activity in animals subjected to mechanical and chemical noxious stimulation. The finding of this study suggests that diurnal variation in pain responses to various noxious stimuli during the harmattan is similar in male and female rats. Also resveratrol did not possess any analgesic properties during the harmattan season. Lastly, mechanical noxious stimulus produced the highest oxidative damage than the chemical and thermal noxious stimulation.