Application of dynamic pupillometer in the evaluation of pupillary light reflex in C57BL/6 mouse

Background Pupillary light reflex has been widely used in the diagnosis and evaluation of visual system and nervous system diseases.However,in animal experiments,functional evaluation of the visual system and nervous system needs more advanced technology and are affected by many factors.Objective This study was to explore the use of the dynamic pupillometer in evaluating pupillary light reflex and to discuss the influence of brightness of stimulate on relevant curve parameters in C57BL/6 mouse.Methods Ten healthy SPF male C57BL/6 mice were collected in this experiment.White light of five luminance levels (2,8,32,128,256 cd/m2) was used to stimulate the mice following a 2-hour dark adaptation.The stimulation was given at the 60-second intervals,for a duration of 100 ms at every stimulation.An infrared camera and video capture card were used to capture digital images during the measuring process in a scotopic environment,at a speed of 60 frames per second.Measuring outcome was saved in the *.AVI format.A software that was developed by our group was used to determine pupil diameter and output pupillary light reflex curve offline.Pupil initial diameter (R1),constriction amplitude (CA),constriction velocity (CV),latency (T1),time for maximum velocity (T2),time for maximum constriction (T3),time for maximun con-striction to 10.1％ R1 re-dilation (RT)and re-dilation velocity (RV)were assessed,and the correlations between luminosity and measuring parameters were analyzed using the Spearman rank correlation.The use of animals followed the Regulations for thd Administration of Affairs Concerning Experimental Animals by State Science and Technology Commission.Results R1 values showed no statistically significant difference among the 5 different luminosity groups(F=1.117,P=0.361).A positive linear correlation was found between stimulating luminosity and CA(r=0.508,P＜ 0.01),but negative correlations were seen between stimulating luminosity and CV or RV (r=-0.625,-0.609,P＜0.01).T1 and T2 values in the 5 different luminosity groups were not statistically significant (F =0.202,P =0.936 ; F =1.584,P =0.195).The different levels of stimulating luminosity showed positive linear correlations with T3 and RT values (r =0.791,0.609,P＜ 0.01).Conclusions The dynamic pupillometer can quantitatively measure the pupillary light reflex of C57BL/6 mice.The pupillary light reflex dynamic curve parameters of mouse were affected by stimulus luminosity levels.These outcomes offer a basis for the application of the dynamic pupillometer system for measuring pupillary light reflex in animal models. Key words: Pupil light reflex;  Psychophysics measurement;  C57BL/6 mouse;  light luminosity;  Neural system;  Visual system