Concentration dependent effect of morphine, aspirin, capsaicin and chili pepper hydro alcoholic extract on thermal and chemical pain model in fruit fly (Drosophila melanogaster)

Pain research using animal models is related to ethical concerns, so invertebrates and insects have been recommended by researchers. In the present study, the nociceptive and antinociceptive effects of capsaicin, aspirin, morphine and chili extract were examined using fruit fly (Drosophila melanogaster) as an alternative for rodent pain model. Stage 3 of larvae and adult state of Drosophila were used. Threshold and maximum reactions were recorded in thermal nociception (using Hot plate) and chemical nociception (Writhing test) at various concentration of acetic acid, capsaicin and chili hydro alcoholic extract. Rolling movement responses were recorded in separate groups (n=7). In adult Drosophila, latency for heat tolerance on hot plate was recorded (n=10), and the effect of morphine and aspirin at different concentrations on pain were examined. Increasing the temperature, acetic acid, capsaicin and chili extract concentration, attenuated the rolling movement in larvae. In adult drosophila, increasing the temperature, diminished tolerance latency on hot plate. In this animal model, increasing the morphine and aspirin concentration diminished responses to pain stimulus. According to our results, it can be suggested that Drosophila melanogaster can be used as a model for investigation on pain physiology and antinoiciception. Painless channel (closest vertebrate homolog of TRAP1 channel) maybe required for thermal and chemical nociception in drosophila. Similar to mammals, treatment with morphine and aspirin may exert these effects through Gi and cox2 respectively.