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 th e remainder of the night. Here, the effects of a single 1 min light pu lse during the night on melatonin synthesis during the following night was investigated in Djungarian hamsters (Phodopus sungorus). It is sh own that the melatonin pattern during the consecutive night is suppres sed to a greater extent than that caused by acute light exposure, indi cating a very effective light memory of the melatonin-generating neuro nal network, possibly a key to understanding the reliability of the ph otoperiod-measuring system.