Hormone system changes linked to the duper mutation in Syrian hamsters involving Cryptochrome 1

The phase of the LH surge is altered in duper mutant Syrian hamsters compared to wild types.

• The stability of the LH surge changes with shifts in the light: dark cycle in duper mutants.
• Immunoreactive PER1 levels in GnRH cells peak earlier in the day in duper hamsters compared to wild types.
• GnRH fibers in the suprachiasmatic nucleus contact cells that produce vasopressin and VIP, indicating a potential site for circadian influence on LH surge timing.
• Duper hamsters retain gonadal function in constant darkness for 8 weeks, unlike wild type hamsters, despite melatonin secretion during the subjective night.
• The findings suggest that the duper allele, a stop codon in a core circadian clock gene, may have significant neuroendocrine roles.

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