Effect of P2X7 receptor activation on the retinal blood velocity of diabetic rabbits.

OBJECTIVE To test the effect of activation of P2X7 receptors on retinal blood velocity in diabetic rabbits. METHODS Immunohistochemical analysis was performed on healthy and diabetic rabbit eyes using P2X7 receptor antibodies. Diabetes was induced using alloxan. Retinal blood velocity was measured with the laser speckle circulation analyzer. Visual function was assessed using electroretinography. RESULTS Cells in inner retinal layers were positive for anti-P2X7 receptor antibodies in healthy rabbits. The distribution of positive cells extended to outer layers and some small vessels stained in diabetic rabbits. When assayed 24 hours after an intravitreal injection of 150 nmol of benzoylbenzoyl adenosine triphosphate (BzATP), a P2X7 agonist, the retinal blood velocity in healthy rabbits was reduced by approximately 30%; this reduction continued for at least 4 weeks. Only in diabetic rabbits did an injection of 50 nmol of BzATP reduce retinal blood velocity by approximately 30% and the amplitudes of electroretinography a waves, b waves, and oscillatory potentials for at least 4 weeks. CONCLUSIONS Soon after the onset of alloxan-induced diabetes, retinal blood velocity and function become more vulnerable to reduction initiated through P2X7 receptors. CLINICAL RELEVANCE Our findings support the hypothesis that the retinal circulation disorder accelerated by activation of P2X7 receptors may be involved in the early changes of diabetic retinopathy.