Timely administration of melatonin accelerates reentrainment to phase-shifted light-dark cycles in the field mouse Mus booduga

The effect of melatonin on the rate of reentrainment after a 6h phase delay and a 6h phase advance in the light-dark (LD) cycle was assayed in the noc turnal field mouse Mus booduga. After a phase delay of 6h in the LD cycle, a single dose of melatonin (1 mg/kg) was administered for three consecutive days at about CT4 (circadian time 4). After a phase advance of 6h in the L D cycle, melatonin was administered for three consecutive days at about CT2 2. Melatonin was found to accelerate reentrainment in both cases. Melatonin -treated animals took significantly fewer cycles to reentrain compared to v ehicle-treated (50% dimethylsulfoxide [DMSO]) and nontreated control animal s.