Human morning/evening preferences has recently been reported to be associat
ed with polymorphism of the 3' flanking region of the Clock gene, which was
the first identified mammalian circadian clock gene. We recorded body temp
erature, spontaneous activity, electroencephalogram and electromyogram for
48 h in mice with Jcl:ICR genetic background and homozygous for the Clock m
utation (Cl/Cl on Jcl:ICR). In both wild-type and Cl/Cl on Jcl:ICR, body te
mperature, activity, wake and sleep were completely entrained to LD cycle.
However, phases of the rhythm for body temperature, activity and wake durat
ion in the Cl/Cl on Jcl:ICR were about 2 h delayed in comparison with the w
ild-type. This study has provided further evidence on the close relationshi
p between human morning/evening preference and the molecular basis of circa
dian clock system, and has suggested that Cl/Cl on Jcl:ICR is useful for an
animal model for human morning/evening preference. NeuroReport 12:1461-146
4 (C) 2001 Lippincott Williams & Wilkins.