Mouse model for morningness/leveningness

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.