Abstract
Common marmosets (Callithrix jacchus), day-active primates, were raised artificially from birth under one of 3 lighting conditions: a 12h light and 12h dark cycle (LD12:12, n=3), constant light (LL, n=4), or constant complete darkness (DD, n=1). Under each condition, spontaneous locomotor activity was detected about 10 days after birth. Marmosets in LD12:12 showed entrained circadian activity rhythms with activity periods corresponded to the light period. In LL, marmosets showed free-running circadian rhythms with periods longer than 24h ( mean 24.71h) during first 2 months. Periods of free-running rhythms begun to decrease around postnatal day 100, and finally they became shorter than 24h until postnatal day 130. In DD, a marmoset showed less activity than animals in LD12:12 and LL. The animal showed a split circadian activity rhythm free-running with a period shorter than 24h (23.5h). On postnatal day 121, the animal was transferred into LD12:12. Behavioral tests suggested that the animal had a severe damage in visual function, however its circadian rhythms quickly entrained to the LD cycle. [J Physiol Sci. 2008;58 Suppl:S94]
