Role of nitric oxide during the initial phase of reperfusion after retinalischemia in the rat

The onset of reperfusion and the recovery of the ERG b-wave following retin al ischemia was examined among three groups of rats: group 1 (n = 12) and g roup 2 (n = 6) received pretreatment with N-G-nitro-L-arginine (20 mg/kg, i .p., 2 h before ischemia) followed by intravenous injection of saline (grou p 1) or of 200 mg/kg L-arginine (group 2) 5 min before the end of ischemia; group 3 (n = 7) received saline pretreatment followed by intravenous injec tion of saline as a control. Group 1 showed delayed onset of reperfusion co mpared to the other two groups and a reduction in the rate of the b-wave re covery compared to the control on the 1st day after reperfusion (group 1 vs . group 3; p = 0.0357). The L-arginine posttreatment significantly increase d the b-wave recovery (group 2 vs. group 1; p = 0.0005 on day 1 and p < 0.0 006 on day 3). The rate of the b-wave recovery in group 1 was inversely pro portional to the time to establish complete reperfusion. Inhibition of nitr ic oxide synthase during the initial phase of reperfusion may worsen the re covery of the b-wave following retinal ischemia, at least in part, by inhib iting establishment of reperfusion.