Responses of retinal arterioles to vasoactive substances. (A) The thromboxane mimetic, U46619, elicited concentration-dependent vasoconstriction in retinal arterioles that was similar in all groups. (B) Likewise, responses to the endothelium-independent vasodilator, sodium nitroprusside (SNP), did not differ between the four groups. (C) In contrast, retinal arterioles from mice subjected to I/R displayed blunted endothelium-dependent vasodilator responses to acetylcholine, which were partially improved by treatment with BA. Values are expressed as the mean ± SE (* p < 0.05, I/R + vehicle versus vehicle; # p < 0.05, I/R + vehicle versus BA; + p < 0.05, I/R + vehicle versus I/R + BA; $ p < 0.05, I/R + BA versus vehicle; & p < 0.05, I/R + BA versus BA; n = 8 per group).