Daily and light-based control of melatonin-making enzyme gene in chicken's pineal gland and eye

AA-NAT mRNA exhibits a circadian rhythm in the chicken pineal gland and retina, with peak levels at night.

• AA-NAT mRNA is detectable specifically in follicular pineal cells and retinal photoreceptors.
• The rhythm of AA-NAT mRNA levels persists under constant darkness and constant lighting conditions.
• Light influences the timing of AA-NAT mRNA peaks, delaying them by approximately 6 hours in constant lighting and advancing them by more than 4 hours with a late-night light pulse.
• Nocturnal AA-NAT mRNA levels remain unchanged during a brief 20-minute light exposure.
• The decrease in AA-NAT activity following light exposure does not correlate with changes in mRNA content.

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