Figure 4. Circadian profile of melatonin release

For melatonin estimation, on day 8 starting at zeitgeber times (ZT) 0, media (1 ml) was collected and replaced simultaneously at the times indicated in the figure. Analysis of variance indicated significant differences between the day and night values of melatonin content (p<0.001) in light-dark (n=5-6) and dark-dark (n=4-6) with concentrations high at night and low during the day.