Figure 3

Circadian profiles of pineal 5-HT and melatonin secretion from multiple inbred PVG and LEW rats. A. Entrained profiles of 5-HT (upper panel) and melatonin (lower panel) secretion from 4 PVG rats. All data points were normalized to the nocturnal peak values of each circadian cycle. Each rat is represented by a different color. 5-HT and melatonin secretion from the same rat is shown in the same color. B. Secretory activities of 5-HT (upper panel) and melatonin (lower panel) from 4 LEW rats. C. Comparison of 5-HT (upper panel) and melatonin (lower panel) secretion profiles from PVG (yellow) and LEW (blue) rats. D. Comparison of 5-HT (upper panel) and melatonin (lower panel) secretion profiles from all 4 strains of rats: SD (red), Wistar (green), PVG (yellow), and LEW (blue) rats. E. Phase angle difference in MT-on between PVG and LEW rats is independent of pineal mechanisms. Norepinephrine (NE, 20 uM) was infused directly into the pineal gland of 2 PVG (ID2294 and ID2297) and 2 LEW (ID2287 and ID2291) rats for 4 hrs (11:00 h-15:00 h; blue shaded area). Data for melatonin secretion at night were normalized to the nocturnal maximum, whereas data between 9:00 h and 15:00 h were normalized to the maximum levels stimulated by the norepinephrine (13:00 h-14:00 h). Compared to PVG rats, appearance of melatonin following norepinephrine stimulation was slightly delayed (10–20 min). This difference was due to the time needed to change drug-filled syringes.