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Altered distribution of synaptic densities at aberrant synapses in the chick cochlear nucleus
1Department of Anatomy, University of Utah School of Medicine, Salt Lake City 84132.
Abstract:
The role of axon-target cell interactions in shaping the prevalence and distribution of synaptic densities was studied in an experimentally-induced aberrant functional projection from the chick cochlear nucleus (nuc. magnocellularis, NM) to the contralateral NM. Contact with an abnormal target appears to induce in the aberrant axons a pattern of presynaptic densities resembling that in normal cochlear nerve endings in NM. NM axon terminals induced similar numbers of postsynaptic densities (PSDs) per unit length of membrane apposition in both their normal and abnormal targets but the longer membrane apposition in the highly invaginated aberrant terminal in NM results in a significantly greater amount of postsynaptic density per ending. These auditory neurons thus appear able to adjust a variety of features to permit assembly and maintenance of a novel functional synapse.
Insights
Auditory neurons can form new functional synapses by adjusting their structure when connecting to abnormal targets. This study shows how axon-target interactions shape synaptic development in the chick cochlear nucleus.
Area of Science:
- Neuroscience
- Developmental Biology
- Synaptic Plasticity
Background:
- Axon-target cell interactions are crucial for establishing functional neural circuits.
- The formation and distribution of synaptic densities are key aspects of synapse development.
- Understanding how neurons adapt to novel connections is vital for neuroscience research.
Purpose of the Study:
- To investigate the role of axon-target cell interactions in shaping synaptic density.
- To analyze how aberrant projections influence synapse formation and maintenance.
- To examine the plasticity of auditory neurons in forming novel functional synapses.
Main Methods:
- Experimentally induced aberrant functional projection from chick cochlear nucleus (NM) to contralateral NM.
- Microscopic analysis of presynaptic and postsynaptic densities at normal and aberrant axon terminals.
- Quantification of membrane apposition and postsynaptic densities (PSDs) per unit length.
Main Results:
- Aberrant axons contacting abnormal targets developed presynaptic density patterns similar to normal cochlear nerve endings.
- Similar numbers of postsynaptic densities (PSDs) per membrane length were induced in both normal and abnormal targets.
- Increased membrane apposition in invaginated aberrant terminals led to a greater amount of postsynaptic density per ending.
Conclusions:
- Auditory neurons demonstrate remarkable adaptability in forming and maintaining novel functional synapses.
- Axon-target interactions play a significant role in regulating synaptic structure and function.
- Synaptic plasticity allows neurons to adjust various features for successful synapse assembly in new contexts.