Changes in body clock gene activity during growth in Syrian hamsters

Bmal1 showed a significant decrease after birth in the Syrian hamster's suprachiasmatic nucleus (SCN).

• Developmental expressions of three clock genes (Bmal1, Cry1, and Per1) were examined in the SCN over the first 4 days post-neurogenesis.
• Transcripts of all three clock genes had higher abundance just after birth, with Bmal1 prominently expressed in the fetal SCN.
• While Per1 continued to be expressed at greater levels than prenatal levels, Bmal1 and Per1 showed no circadian variation.
• Significant variation in Cry1 expression was detected across circadian times, but not for Per1 and Bmal1.
• Molecular oscillations seen in adults were absent in the fetal SCN, suggesting a different developmental pattern.
• The lack of robust oscillations during early SCN development may contribute to strong phase-setting effects from pharmacological agents.

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