神經保護藥物在大鼠視網膜缺血模式中的保護效力

Abstract

本實驗的目的為評估兩種具有神經保護功能的藥物: Brimonidine及 Phenylbutyrate (PBA)對於大鼠視網膜缺血傷害(retinal ischemic injury)是否有保護能力及其保護效力。在成年Sprague-Dawley大鼠，先利用螢光追蹤器Fluorogold(FG)放置在四疊體上丘上方以達成回溯性標定視網膜神經節細胞(RGCs)。七天之後，以高眼壓方式製造大鼠視網膜缺血。藥物治療分為三組，視網膜缺血一小時前點眼投與0.2% Brimonidine於大鼠左眼；視網膜缺血前30分鐘，以腹腔注射100 mg/kg或400 mg/kg PBA；視網膜缺血後一個小時，以腹腔注射400 mg/kg PBA。在視網膜缺血後七天，將大鼠犧牲，取下視網膜後，在標準的16個區域計算FG-labeled RGCs數量，評估存活的RGCs數目。另一方面，也是在視網膜缺血後七天，將眼球取下固定製作組織病理切片。120 mmHg，45分鐘的視網膜缺血會造成FG-labeled RGCs 18.7%的喪失。但是缺血前給予0.2% Brimonidine點眼的視網膜只有喪失6.74%的FG-labeled RGCs。在缺血前給予高劑量或低劑量的PBA可以幾乎100%的保護RGCs但是缺血後給予PBA對於RGCs卻沒有保護效果。缺血前給予Brimonidine點眼治療及缺血前給予PBA都可以有意義的減少視網膜、內層視網膜、內叢狀層厚度的消失及減少神經節細胞層及內核層細胞的喪失。這些結果都可以揭示Brimonidine與PBA對視網膜缺血是有保護能力。

The purpose of this study was to investigate the effects of two neuroprotective agents: Brimonidine and Phenylbutyrate (PBA), in retinal ischemic injury of rats. In adult Sprague-Dawley rats, RGCs were retrograde labeled with fluorescent tracers Fluorogold (FG) applied to both superior collicoli. Seven days later, the high intraocular pressure was induced. Medications were divided into three groups: one hour prior to retinal ischemia, 0.2% Brimonidine was instilled on the left eye; 30 minutes prior to retinal ischemia, 100 mg/kg or 400 mg/kg PBA were injected intraperitoneally; one hour after retinal ischemia, 400 mg/kg PBA was injected intraperitoneally. Rats were processed 7 days later and densities of surviving RGCs were estimated by counting FG-labeled RGCs in 16 standard regions of each retina. On the other hand, histological outcomes were also determined at 7 days after retinal ischemia. 120 mm Hg for 45 minutes ischemic injury caused 18.7% loss of FG-labeled RGCs and after the treatment of Brimonidine only 6.74% of FG-labeled RGCs were lost. Almost 100% RGCs could survive by pre-ischemic treatments of PBA but post-ischemic treatment of PBA cannot rescue RGCs from IR injury. Pre-ischemic treatment with Brimonidine and pre-ischemic treatment of PBA significantly reduced loss of thickness of retina, inner retina, and inner plexiform layer and reduced loss of cells in the ganglion cell layer and inner nuclear layer. Although post-ischemic treatment of PBA cannot rescue cells in ganglion cell layer but can reduce loss of thickness of retina, inner retina, and inner plexiform layer and reduced loss of cells in the inner nuclear layer. These results indicate that both Brimonidine and PBA have neuroprotective effects on retinal ischemia.