Figure 2.
NO modulates light-evoked vasomotor responses. A, Light-evoked vasodilation is transformed into a vasoconstriction by addition of the NO donor SNAP (100 μm). The vessel dilates in the presence of SNAP and responds to a decrease in pH of the superfusate with an additional dilation. B, Light-evoked vasoconstriction is transformed into a vasodilation by addition of the NO scavenger PTIO (100 μm). The vessel dilates in the presence of PTIO. C, PTIO increases the duration of a light-evoked vasodilation. D, Raising NO levels increases the percentage of vessels that constrict to light stimulation. At <70 nm NO, light stimulation evoked vasodilation in all vessels (n = 12). As NO was raised, a greater percentage of vessels constricted. E, Schematic of arachidonic acid metabolism, showing synthesis of vasoactive EETs, prostaglandins, and 20-HETE. Synthetic enzymes are italicized and enzyme inhibition is indicated by an X.