Changes in a key light-sensitive gene in the eye and pineal gland of rats under different day lengths

The time span between the onset of darkness and the nocturnal rise in AA-NAT mRNA expression was 3 hours under LD 20:4, 6 hours under LD 12:12, and 15 hours under LD 4:20.

• Arylalkylamine N-acetyltransferase (aa-nat) gene expression was examined in the retina and pineal gland of adult Sprague-Dawley rats.
• Both the retina and pineal gland showed identical temporal patterns of AA-NAT mRNA expression under different light-dark cycles.
• The study indicates that photoperiodic responses are reflected in multiple circadian oscillators.
• The results may highlight the significance of seasonal changes in regulating biological rhythms.

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