AI Article Synopsis
- The study investigated how the activity of the enzyme AA-NAT, crucial for melatonin production, changes in the retinas and pineal glands of turkeys under constant light and dark conditions.
- After 7 days in constant darkness, the retina's AA-NAT rhythm diminished after 5 days, while the pineal gland maintained a consistent rhythm, suggesting a difference in how these tissues respond to environmental changes.
- In both tissues, reintroducing light-dark cycles helped restore the AA-NAT rhythm, indicating that the turkey retina is more sensitive to light changes than the pineal gland, which seems to retain some rhythmic melatonin production even when exposed to light, unlike in mammals.
Article Abstract
Dynamics of rhythmic oscillations in the activity of arylalkylamine N-acetyltransferase (AA-NAT, the penultimate and key regulatory enzyme in melatonin biosynthesis) were examined in the retina and pineal gland of turkeys maintained for 7 days in the environment without daily light-dark (LD) changes, namely constant darkness (DD) or continuous light (LL). The two tissues differentially responded to constant environment. In the retina, a circadian AA-NAT activity rhythm disappeared after 5 days of DD, while in the pineal gland it persisted for the whole experiment. No circadian rhythm was observed in the retinas of turkeys exposed to LL, although rhythmic oscillations in both AA-NAT and melatonin content were found in the pineal glands. Both tissues required one or two cycles of the re-installed LD for the full recovery of the high-amplitude AA-NAT rhythm suppressed under constant conditions. It is suggested that the retina of turkey is less able to maintain rhythmicity in constant environment and is more sensitive to changes in the environmental lighting conditions than the pineal gland. Our results indicate that, in contrast to mammals, pineal glands of light-exposed galliformes maintain the limited capacity to rhythmically produce melatonin.
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| http://dx.doi.org/10.1007/s00359-008-0363-x | DOI Listing |
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