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Correlation of nitric oxide synthase expression with changing patterns of axonal projections in the developing visual
C V Williams1, D Nordquist, S C McLoon
1Department of Cell Biology and Neuroanatomy, University of Minnesota, Minneapolis 55455.
Summary
Nitric oxide synthase (NOS) is present in the developing chick optic tectum, coinciding with retinal axon innervation. This suggests nitric oxide plays a role in forming precise visual system connections.
Area of Science:
- Neuroscience
- Developmental Biology
- Neurochemistry
Background:
- Precise neural connections in the visual system form during development.
- Activity-dependent mechanisms and NMDA receptors are crucial for this process.
- Nitric oxide (NO) is a newly described neurotransmitter potentially involved in neural development.
Purpose of the Study:
- To investigate the presence and role of nitric oxide synthase (NOS) in the developing chick retinotectal system.
- To determine if NO acts as a retrograde messenger in pattern formation.
Main Methods:
- Diaphorase histochemical technique to detect NOS.
- Wheat germ agglutinin/horseradish peroxidase (WGA/HRP) labeling to trace retinal axons.
- Northern blot analysis to verify NOS expression.
Main Results:
- NOS is present in the developing chick optic tectum.
- NOS expression temporally coincides with retinal axon innervation and connection refinement.
- NOS-positive cells' processes extend into areas innervated by retinal axons.
- NOS expression is dependent on retinal axons, indicating retinal input onto NOS-expressing cells.
Conclusions:
- Nitric oxide synthase is present in the developing chick retinotectal system.
- Nitric oxide likely plays a role in guiding the formation of precise neural connections in the visual system.
- Retinal axons may synapse onto NOS-expressing cells, suggesting a role for NO in retrograde signaling during development.