| [Background and Objective]Diabetic retinopathy (DR) is one of the serious complications of diabetes mellitus (DM) and is also the most important cause of blindness. But until now, there is no understanding of its occurrence mechanism and no effective drug or treatment to control the development of the disease. This study is trying to find the forming mechanism of experimental DR from the aspect of retinal vassles and neurosensory retina, and further to find out the theraputic effects of some drug such as nerve growth factor (NGF) and aminoguanidine (AG).[Methods]Diabetes was induced in ninety-six adult male Wistar rats with a single dose of 45 mg/kg of streptozotocin (STZ) administered intravenously. Rats were divided into the following groups: normal control group(CON), diabetes control group(DM), NGF-treated group(D+N) and AG-treated group(D+A). The visual evoked potential (VHP) was measured every 3 months, 6months, 9months and 12months separately. Ultrathic sections were taken from the rat eyes and optic nerve and observed under light microscope and transmission electron microscope.[Results]1. The diabetic animal models which was induced by STZ in Wistar rats have a relatively high rate of success and steady process. The DM group shows a significant increase in blood glucose (P<0.01) and a significant decline in body weight (P<0.Ol).The D+N group has no significant changes in blood glucose or body weight. The D+A group has a significant decline in blood glucose (P<0.01) and an increase in body weight (P<0.01) compared with the DM group.2. At every experimental time point, there was significant difference between DM group and CON group (P<0.01), as shown on the elongated latency and declined amplitude of DM rats. At 6th and 9th month, the latencies of group D+N and group D+A significantly decreased (P<0.05) and the amplitude resurged only at 6th month. At 12th month, no significant changes were observed in latency or amplitude other than that the amplitus of AG treatment group has a little increase compared with DM group.3. From the 3th month on, we observed that the nuclears of endothelial and pericytes cells in retina vessles were distorted, condrocyte swelled, basement membrane increased, retinal ganglion cell swelled, the condrocyte degenerated, membrane disk spaces of photoreceptors (rods and cone) were enlarged. The optic nerve fibers were degenerated, myelinolysis were dropouted in different extent, glial cells were proliferated. All these pathological changes were getting worse gradually with the progression of DR.4. With the treatment of NGF and AG, all the abnormalities were improved, such as the membrane disk spaces shrinked, neural cells processes were little swelled.[Conclusions]1. The diabetic animal model which was induced by STZ in adult male Wistar rats was a successful and steady diabetic model. The DM group has a significant increase in blood glucose and decline in body weight.2. The VHP impairment which is characterized by significant elongated latency and declined amplitude has been detected in diabetic rats. There were also in some extent pathomorphology changes in the retinal vessles, photoreceptors, ganglion cells and optic nerves.3. NGF has no significant effects on the general diabetic index such as blood glucose and body weight, but it could prevent the abnormal changes of VHP by decreasing the elongated latency and rising the descented amplitude. With the treatment of NGF, the pathomorphology changes showed the theraputic effects of NGF on ganglion cells and neural cells.4. The treatment of AG showed a wide theraputic effects on the general index, latency of VHP and the pathomorphology changes of retina and optic nerve.5. We did not find the obvious causal relationships among the impairment of retinal vassles, neurosensory retina and optic nerve. So the conclusion could be drawn that all the changes existed simultaneously and they might affect each other and jointly lead to DR as well as the impariment of visual function.
|
PDF Full Text Request