MELATONIN ACCELERATES REENTRAINMENT OF CIRCADIAN LOCOMOTOR-ACTIVITY RHYTHMS TO NEW LIGHT-DARK CYCLES IN THE RAT

We examined whether continuous melatonin administration through subcut aneously implanted silastic tubing accelerates reentrainment of circad ian rhythms of locomotor activity to shifted illumination cycles. We f ound that rats required less time to reentrain to an advanced or delay ed phase shift of a light-dark cycle while carrying a silastic implant filled with melatonin than while carrying an empty implant. These res ults suggest that continuous administration of melatonin accelerates t he reentrainment of the circadian locomotor activity rhythm to a new l ight-dark cycle.