Objective: Study the effect of Vaccinium uliginosum (VU) on the electroretinogram (ERG) and histology of rabbits' retina before and after light-induced damage.
Methods: It was an experimental study in contrast. Thirty-five Chinchilla Rabbits were divided into five groups according to the randomization tables. All rabbits ate and drank freely except those in group A and D who were fed with VU homogenate. Four weeks later we observed the tissue & structure of the rabbits in group D and E under the light microscope and measured the thickness of their out nuclear layers (ONL) and apoptosis index (AI). At the same time, we recorded maximal combined reaction ERG and oscillatory potentials (oscillatory potentials, OPs) of the left rabbits according to the standards set by the International Society for Clinical Electrophysiology of Vision (ISCEV). Then group A, B and C were exposed to strong light. Also we stopped feeding group A with VU and start to feed group C with it. We recorded ERG of them all after 1 day, 1 week and 2 weeks respectively. Then we observed the tissues & structures of them. SPSS 12.0 software package was used for one-way or double ways ANOVA and LSD test.
Results: (1) Maximal combined reaction ERG: after four weeks feeding implicit time of group A: a wave (14.079+/-0.841) ms, b wave (35.629+/-6.865) ms; amplitude: a wave (83.936+/-10.807) microV, b wave (280.931+/-27.807) microV. Two weeks after injury implicit time of group A: a wave (15.571+/-1.087) ms, b wave (38.915+/-7.683) ms, amplitude:a wave (66.478+/-9.709) microV, b wave (245.887+/-11.797) microV. After four weeks feeding implicit time of group B: a wave (15.635+/-1.661) ms, b wave (42.985+/-3.164) ms; amplitude: a wave (69.331+/-12.355) microV, b wave (197.331+/-16.157) microV. Two weeks after injury implicit time of group B: a wave (18.783+/-1.966) ms, b wave (52.322+/-4.784) ms, amplitude:a wave (57.562+/-8.217) microV, b wave (159.569+/-17.859) microV. After four weeks feeding implicit time of group C: a wave (15.115+/-0.940) ms, b wave (43.242+/-4.662) ms, amplitude: a wave (72.812+/-4.403) microV, b wave (207.815+/-14.373) microV. Two weeks after injury implicit time of group C: a wave (15.957+/-2.154) ms, b wave (44.081+/-9.506) ms, amplitude: a wave (66.804+/-8.755) microV, b wave (186.271+/-29.349) microV. These three groups had statistical significance in maximal combined reaction ERG (implicit time of a wave: fed 4 weeks F=6.057, P<0.05; two weeks after injury F=13.296, P<0.05. Implicit time of b wave: fed 4 weeks F=9.949, P<0.05; two weeks after injury F=11.145, P<0.05. Amplitude of a wave: fed 4 weeks F=8.468, P<0.05; two weeks after injury F=4.844, P<0.05. Amplitude of b wave: fed 4 weeks F=70.194, P<0.05; two weeks after injury F=62.161, P<0.05). The total amplitudes of OPs (OPs=OPs1+OPs2+OPs3) of them had statistical significance (fed 4 weeks F=17.482, P<0.05; two weeks after injury F=11.748, P<0.05). By LSD test we found that before injury the amplitude of a wave and b wave in group B and C in maximal combined reaction ERG were significantly lower than those of group A which was fed by VU for 4 weeks (the a wave and b wave of group B compared to A: P=0.003, 0.000; the a wave and b wave of group C compared to A: P=0.001, 0.000). After light-induced injury, the implicit time of all the groups was increased and amplitude was decreased. But after the injury time of 1 day, 1 week and 2 weeks, the amplitude of b wave of group A was respectively (229.743+/-11.978) microV, (212.785+/-21.021) microV, (245.887+/-11.797) microV, which was significantly higher than group B in the same period (P=0.000). With the accumulation of VU the ERG of group C was improving. Two weeks after injury the implicit time of b wave in group C was (44.081+/-9.506) ms and the amplitude was (186.271+/-29.349) microV. Compared with group B the former was decreased and the latter was increased significantly (implicit time: P=0.008; amplitude: P=0.007). (2) Group D and E were normal in histology and layers were in order. While group B got disordered. Group A and C were injured slightly. The thickness of ONL among all groups had statistical significance (F=330.506, P<0.05). (3) There was statistical significance among all groups in AI (F=230.126, P<0.05). AI of group B was (10.960+/-1.534)% and was higher than others' (P=0.000). AI of group D was (1.817+/-0.203)% and lower than group E (P=0.000).
Conclusions: Vaccinium uliginosum can decrease retinal cell apoptosis and reduce photochemical damage to retinal tissue. In addition VU is able to promote retinal repairing after light damage.