Methods: We divided the animal (3 weeks male Wistar rats) into three experimental groups; 1) hard food (HF) group (12 weeks), 2) soft food (SF) group (12 weeks), 3) mix food (MF) group (soft food for 10 weeks, and then hard food for 2 weeks). We assessed oxidative stress in the brain using the in vivo L-band electron spin resonance (ESR) technique and dopamine (DA) release in the hippocampus using a microdialysis. We measured the scavenge activity of hydroxyl radical (HO.) by DA using in vitro X-band ESR technique. All groups were measured the weight after end of experimental period. Statistical analyses were performed Student's t-test and post hoc test.
Results: There were no significant differences in weight between each group. The significant increase of oxidative stress in the brain (P<0.05) was observed in SF and MF group. SF group had the significant decrease in DA release in the hippocampus. In addition, DA significantly deceased on HO. generation in vitro.
Conclusions: We demonstrated that the treatment with SF induced oxidative stress in the brain, and that they reduced DA release in hippocampus. Further, DA had a scavenge activity on HO. generation system, directly. These results suggested that HO. generated by change of mastication with the differences of food textures was reduced DA in hippocampus, and it was likely that they may be induced the adverse effects of brain function.