CycLuc1 allows for millisecond acquisition of in vivo bioluminescence images from the PVN. A: original bioluminescent images, using a standard exposure of 60 s or a rapid exposure of 1,500 ms, of photon emission from the PVN after d-luciferin or CycLuc1 substrate administration. All images are plotted on the same scale. B: the average radiance during continuous capture of 1,500 millisecond images (75 frames) following d-luciferin or CycLuc1 administration (n = 3/group). C: fold enhancement of CycLuc1 (CycLuc1/ d-luciferin) bioluminescent emission from the PVN with a 60 s or 1,500 millisecond exposure (n = 3/group). *P < 0.05 when comparing the area under the curve (see text for additional details).