Liposomal Prostaglandin E 1 Enhances Optic Nerve Head Blood Flow in Cats

We investigated the effects of intravenous administration of prostaglandin E₁ (PGE₁) and lipo-prostaglandin E₁ (lipo-PGE₁), on optic nerve head blood flow (ONHBF) using ten anesthetized cats. Changes in relative ONHBF were noninvasively and continuously measured with fundus camera-based laser Doppler flowmetry. The blood pressure (BP) decreased significantly by 6 ± 5 (mean ± SD)% and 8 ± 4%, respectively, after PGE₁ (30, 100 ng/kg/min) administration, but at either of these concentrations there were no significant changes in ONHBF. On the other hand, with lipo-PGE₁ (10 ng/kg/min), the BP remained unchanged, but ONHBF increased significantly by 61 ± 49%. A larger dose of lipo-PGE₁ (30 ng/kg/min) had opposite effects because the BP decreased significantly by 14 ± 4% after administration, and the ONHBF remained unchanged (i.e., 67 ± 102%). In all cases, there were no changes in IOP. With 10 ng lipo-PGE₁, the large increase in ONHBF can be accounted for by vasodilation since perfusion pressure was unchanged. The inability of 30 ng lipo-PGE₁ to affect ONHBF could be ascribed to the decrease in BP resulting in decreased ocular circulation. These results suggest that, in humans, lipo-PGE₁ may also increase ONHBF provided that it is used at doses that do not produce large decreases in BP.