4. Discussion
This study demonstrates the cognitive-enhancing effect of LA and its positive modulation effect on oxidative stress and cholinergic function. In this study, a blue or violet laser beam at a wavelength of 405 nm was applied at the HT7 acupoint. Because the laser beam used in this study was a low-energy beam, this treatment is also referred to as low-level laser therapy(LLLT). LLLT is believed to produce photochemical, rather than thermal, effects because low irradiation levels are used and because no appreciable temperature rise takes place [11]. LLLT may decrease the oxidative stress in oxidatively stressed neurons [12]. However, rats that had undergone LA at sham acupoints, both in the ACSF and the AF64A-treated groups, showed no changes in MDA levels in
their hippocampus. A possible explanation for the discrepancy between our study and the aforementioned study
might be the differences in the selected brain areas and the types of exposure. This study was an in vivo study, whereas the previous study was an in vitro study.LA at HT7 significantly enhanced the CAT and the SOD
activities without significantly changing the MDA level in the hippocampus. These data suggest that the restoration of oxidative stress balance might not play an important role in the cognitive-enhancing effect of LA. In contrast to the MDA change, rats subjected to LA showed suppressed elevations of AChE activity, which in turn indirectly reflected the elevation of ACh in the hippocampus. Because Ach plays an important role in learning and memory and because the AChE inhibitor can also reduce memory impairment in Alzheimer’s disease, we suggest that LA at HT7 may improve cholinergic function in the hippocampus,which in turn gives rise to enhanced spatial memory capacity in an animal model of Alzheimer’s disease, as observed in this study.
In conclusion, this study is the first study to demonstrate the positive modulation effect of LA at HT7 on the cholinergic function, which in turn leads to reduced cognitive impairment in an animal model of Alzheimer’s disease.