6-Formylpterin protects retinal neurons from transient ischemia-reperfusion injury in rats: A morphological and immunohistochemical study

Neuroprotective effects of 6‐formylpterin (6FP) on transient retinal ischemia–reperfusion injury were evaluated in rats by means of counting the number of retinal ganglion cells, measuring the thicknesses of the inner plexiform and inner nuclear layers, and by immunohistochemical detection of apoptotic cells in the retina. Sixty‐one Sprague–Dawley rats (12 weeks, male, 295–330 g) were subjected to transient retinal ischemia–reperfusion by elevated intra‐ocular pressure (80 mmHg for 60 min). Intraperitoneal injection of 6FP (3.8 mg/kg) was performed before or after ischemia. The retina was histologically better preserved in rats with 6FP treatment than without 6FP treatment. 6FP showed more strong neuroprotective effects when it was administered before ischemia. The number of single‐stranded DNA‐positive cells in the retina also decreased remarkably in rats with 6FP treatment, especially when administered before ischemia. These results suggest that 6FP protects retinal neurons from transient ischemia–reperfusion injury, at least in part by inhibiting apoptotic cell death.