LOW LEVEL LASER THERAPY IMPROVES LEARNING AND MEMORY FUNCTIONS IN NEONATAL RATS FOLLOWING HYPOXIC ISCHEMIC BRAIN INJURY

摘要

Purpose/Hypothesis : It has been reported that low level laser therapy (LLLT) can reduce pain andinflammation. It can also improve local microcirculation in all species. The main purpose of this study wasto determine whether LLLT reduces brain injury, facilitates learning and memory improvement in neonatalrats following hypoxic ischemic brain injury. Subjects: Eighteen seven-day-old rat pups were used in thisstudy. The pups were randomly divided into three groups: control (C, n=3), ischemic control (IC, n=7) andLLLT treatment group (LLLT, n=8). Methods: After anesthesia, all pups had right carotid arteries ligatedfollowed by 140 minutes of hypoxia (8% oxygen). The pups in the control group had no injury and receivedno treatment. The pups in the ischemic control group had hypoxic exposure, but received no treatment. Thepups in the treatment group received LLLT after hypoxic exposure. LLLT treatment was achieved by placingthe laser probe on the top of the each pup head for 2 treatment cycles (33 seconds/per treatment cycle), twicedaily for two weeks. Brain damage was evaluated by weight deficits of the right hemisphere at the end of 22days post treatment. Behavioral functions including learning and memory were evaluated at 22-23 daysfollowing hypoxia using a passive avoidance test. Learning index was obtained by recording the number ofelectric shocks to retain rats in the safety board. Memory index was obtained by recording the length of timefor rats to stay in the safety board 24 hours after the learning index was recorded. Extremity strength wasexpressed with latency to fall from spinning rail.Results: data obtained from this study revealed that LLLT reduced brain weight loss and brain damage inthe right hemisphere from -26.3±7.45% and 57.13±9.8 in the IC group to -15.94±6.1% and 37.5±9.0 inLLLT group, respectively, however, it was determined to statistically insignificant (P=0.26). Learning andmemory indexes were improved from 41.3±11.0 and 59.0±21.2 in the IC to 12.1±0.9 (p<0.05) and 95.5±7.3(p=0.1) in the LLLTP, respectively. The latency to fall in the IC and LLLT group were 119.5±37.0 and118.0±36.0, respectively. Conclusions: The results indicated that LLLT has neuroprotective effects inreducing brain damage and improving learning and memory in neonatal rats following hypoxic ischemicinjury. Clinical Relevance: LLLT is an effective intervention to reduce brain deficits in the rat model. LLLTmay be considered as an ideal modality to improve functional outcomes in clinical setting that expressneurologic disturbances.