Effect of Laser Irradiation on Non-spatial Memory of Mice

Objective To investigate and analyze the effect of laser irradiation on the non-spatial memory of mice,the hippocampus of mice is exposed by means of the different radiation exposure,wavelength and emission mode of laser irradiation in vitro and followed on test in the non-spatial maze. Methods Laser exposure device used in the experiment of laser irradiation on mice,including Nd ∶YAG pulsed laser and semiconductor laser,measuring instruments and software of computer detection and control has been specially designed and built up.Laser wavelengths of the pulse laser in the system were 1 064 nm and 532 nm,and wavelength of semiconductor continuous wave(cw) laser were 659 nm and 532 nm.The beam diameter was 5 mm.The maximum output of laser was 180 mJ.Eighty of Kunming(KM) mice were divided into 11 groups to perform the experiments of laser irradiation on the mice hippocampus as well as the test of non-spatial maze.The time that mice got out of the maze pre-and post-irradiation was compared. Results(1) The pulsed laser groups: for laser wavelength of 532 nm and 1 064 nm,the time that mice got out of the maze was not significantly different by contrast of the pre-irradiation when the irradiance of cerebral cortex was respectively 2.79×1010 W/m2 and 6.90×1010 W/m2,but the time was distinctly prolonged when the irradiance of cerebral cortex was respectively 8.50×1010-4.60×1011 W/m2 and 2.40×1011-1.61×1012 W/m2.(2) The continuous laser groups: for laser wavelength of 532 nm and 659 nm,the time that mice got out of the maze was significantly prolonged when the radiation exposure of cerebral cortex was respectively 8.90×103-2.64×104 J/m2 and 1.75×104-5.30×104 J/m2 and that the exposure time was 15 min/d.In the continuous irradiation for three days,the time of the mice got out of the maze had no statistical significance when the second day compared with the first day,but the time was significantly prolonged when the third day compared with the first day. Conclusions Both the pulsed laser and CW laser can reduce the memory ability of the mice.The biological effect of laser is relative to the radiation exposure,wavelength and emission mode of laser,and that laser irradiation exists certain cumulative effect in biology.