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Optic nerve transection decreases 2-[125I]iodomelatonin binding in the chick optic tectum
D N Krause1, J A Siuciak, M L Dubocovich
1Department of Pharmacology, College of Medicine, University of California, Irvine 92717.
Brain Research
|September 11, 1992
Summary
This study found presynaptic melatonin receptors on chick optic nerve axon terminals. Melatonin receptor binding decreased in the optic tectum after optic nerve transection, indicating their location on these fibers.
Area of Science:
- Neuroscience
- Neuroanatomy
- Receptor Pharmacology
Background:
- Melatonin is a hormone involved in circadian rhythms.
- The optic tectum processes visual information.
- The role of melatonin receptors in the optic tectum is not fully understood.
Purpose of the Study:
- To investigate the distribution of melatonin binding sites in the chick optic tectum.
- To determine if melatonin receptors are located on retinotectal projections.
Main Methods:
- Quantitative receptor autoradiography was used to analyze melatonin binding sites.
- Unilateral optic nerve transection was performed in chicks.
- Melatonin receptor binding was assessed at 1, 7, and 14 days post-transection.
Main Results:
- Specific 2-[125I]iodomelatonin binding sites were identified in the chick optic tectum.
- Following optic nerve transection, a significant decrease in binding was observed in the optic fiber layer and superficial retinorecipient layers of the contralateral tectum at 7 and 14 days.
- No significant change in binding was noted at 1 day post-transection.
Conclusions:
- The findings suggest the presence of presynaptic melatonin receptors on the axon terminals of retinotectal fibers.
- Melatonin may play a role in modulating visual information processing within the optic tectum via these presynaptic receptors.