RESUMO
OBJECTIVE: To investigate the electrophysiological and morphological changes of retinae after intravitreal injection of cyclosporin A (CsA) in experimental diabetic rats. METHODS: Experimental study. SD diabetic mellitus (DM) rat models were induced with intraperitoneal injection of streptozotocin. The rats were divided into four groups, with 9 rats in each group:the normal control (group CON), the diabetic rats with or without CsA intravitreal injection respectively (group DM + CsA and group DM), and the diabetic rats with dimethyl sulfoxide (DMSO) intravitreal injection (group DM + DMSO). The intravitreal injection of CsA or contrast solution was performed 4 weeks after the modeling. The retinal function of rats was examined by electroretinogram (ERG) 48 hours after the intravitreal injection. All rats were sacrificed and the structural changes of retina were observed by optical and transmission electron microscope. The datas of ERG including amplitudes and latencies of a-wave and b-wave were analyzed by One-way ANOVA and Bonferroni post hoc test. RESULTS: There was difference in ERG b-wave among the 4 groups under different stimuli light intensity (F = 14.760 - 28.890, all P value < 0.01). And there was difference in ERG a-wave among the 4 groups when the stimuli light intensity ≥ -0.35 log cd×s×m(-2) (F = 12.510, 15.500, both P value < 0.01). Comparing to the group CON (ERG a-wave: 82.43 ± 26.68, ERG b-wave: 208.40 ± 51.20), the ERG a-wave and b-wave amplitudes of group DM (ERG a-wave: 39.71 ± 7.61, ERG b-wave: 92.20 ± 24.42) and group DM + DMSO (ERG a-wave: 37.63 ± 17.25, ERG b-wave: 93.11 ± 22.50)(t = 5.448 - 7.872, all P value < 0.05), and the ERG b-wave of group DM + CsA (160.10 ± 43.39) (t = 3.299, P < 0.05) were declined in dark adaptation, while the ERG a-wave (63.91 ± 20.32) of group DM ± CsA had no difference (P > 0.05). The a-wave and b-wave amplitudes of group DM + CsA were significantly increased compared to the other two groups in dark adaptation (t = 3.203 - 4.759, both P < 0.05). Under optical microscope, group DM, DM + DMSO and DM + CsA had outer nuclear layer (ONL) disorder. Under transmission electron microscope, there were ultrastructure changes of the three groups. Furthermore, the ONL disorder and ultrastructure changes of group DM + CsA were less severe than the other two groups. CONCLUSIONS: Functional and morphological changes are evident in the early stages in DM rats. Intravitreal injection with CsA shows protective effects on the nerve function in DM retina.
