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Involvement of nitric oxide in the elimination of a transient retinotectal projection in development
H H Wu1, C V Williams, S C McLoon
1Department of Cell Biology and Neuroanatomy, University of Minnesota, Minneapolis 55455.
Abstract:
The adult pattern of axonal connections from the eye to the brain arises during development through the refinement of a roughly ordered set of connections. In the chick visual system, refinement normally results in the loss of the ipsilateral retinotectal connections. Inhibition of nitric oxide synthesis reduced the loss of these transient connections. Because nitric oxide is expressed by tectal cells with which retinal axons connect and because reduction of nitric oxide synthesis by tectal cells resulted in a change in the connections of retinal axons, nitric oxide probably serves as a messenger from tectal cells back to retinal axons during development.
Insights
Nitric oxide plays a key role in the developing chick visual system. Inhibiting nitric oxide synthesis prevents the loss of transient connections between the eye and brain.
Area of Science:
- Neuroscience
- Developmental Biology
- Visual System Development
Background:
- The adult visual system forms through refinement of initial axonal connections.
- In chicks, this involves the loss of transient ipsilateral retinotectal connections.
Purpose of the Study:
- To investigate the role of nitric oxide in the refinement of retinotectal connections.
- To determine if nitric oxide acts as a developmental signal in the visual system.
Main Methods:
- Inhibition of nitric oxide synthesis in the chick visual system.
- Observation of retinotectal connection patterns.
- Analysis of nitric oxide expression in tectal cells.
Main Results:
- Inhibition of nitric oxide synthesis reduced the loss of transient ipsilateral retinotectal connections.
- Nitric oxide is expressed by target tectal cells.
- Reduced nitric oxide synthesis by tectal cells altered retinal axon connections.
Conclusions:
- Nitric oxide likely functions as a retrograde messenger from tectal cells to retinal axons during visual system development.
- This signaling pathway is crucial for the precise wiring of the visual system.