Sustained response of pineal melatonin synthesis to a single one-minute light pulse during night in Djungarian hamsters (Phodopus sungorus).

Previous experiments have demonstrated that short light pulses during the night suppress pineal melatonin formation almost completely for the remainder of the night. Here, the effects of a single 1 min light pulse during the night on melatonin synthesis during the following night was investigated in Djungarian hamsters (Phodopus sungorus). It is shown that the melatonin pattern during the consecutive night is suppressed to a greater extent than that caused by acute light exposure, indicating a very effective light memory of the melatonin-generating neuronal network, possibly a key to understanding the reliability of the photoperiod-measuring system.