Clock protein's role in developing brain signals that regulate daily rhythms

The number of vasopressin (AVP) neurons is significantly reduced in Clock mutant mice compared to wild type.

• Clock homozygous mice do not exhibit the increase in VIP-immunoreactive neurons from postnatal day 6 to P30 seen in wild type mice.
• AVP-immunoreactive neurons remain relatively constant in the postnatal suprachiasmatic nucleus (SCN) but are significantly lower in Clock mutant mice.
• The impact of the Clock mutation on AVP and VIP expression varies by position within the SCN.
• Densitometry analysis shows that Clock mutation specifically reduces AVP expression in the SCN, with no effects observed in other brain regions.
• The neonatal mouse SCN contains its full complement of cells, although some are not fully mature regarding neuropeptide content.
• The findings suggest heterogeneity among AVP and VIP cell classes within the SCN.

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