CycLuc1 enhances in vivo bioluminescence imaging of gene expression in the PVN. A: schematic of the PVN. 3V, third ventricle. B: representative immunohistochemistry demonstrating robust firefly luciferase expression in the PVN following targeted AdCMV-luc administration. Scale bar = 50 μm. C: original bioluminescent images of photon emission from the PVN at 6, 10, 60, and 120 min after substrate injection of d-luciferin (150 mg/kg) or CycLuc1 (5, 7.5, and 15 mg/kg). All images are from the same animal and plotted on the same scale. The areas of high photon emission are displayed in red, and the areas of low photon emission are displayed in blue. D: temporal measurements of PVN bioluminescent emission from 2 to 120 min following substrate administration; n = 8.