Figure 5: Blood melatonin levels in intact (solid line; n= 8), P-X (dashed line; n= 6), and P-X/melatonin infused (dotted line; n= 4) pigeons sampled in DD via an indwelling venous cannula at two hour intervals for 24 hours. P-X infused pigeons whose blood melatonin levels are shown here received 0.70 ug melatonin/hr for 10 hours on the day of sampling. The first data points (0400) have been replotted at 2800. Top panel - Individual pigeon (#680) Bottom panel - Summary graph of the average values (+ SEM); intacts, n=8; P-X, n=6; P-X/melatonin infused, n=4.