Synaptic remodelling during development and maturation: junction differentiation and splitting as a mechanism for...

Area of Science:

• Neuroscience
• Developmental Biology
• Cell Biology

Background:

• Synaptic active zones are critical for neuronal communication.
• Understanding their maturation is key to comprehending brain development and function.
• Previous research has focused on early development, leaving later maturation less explored.

Purpose of the Study:

• To investigate the morphological changes of synaptic active zones during later development and maturation in the rat occipital cortex.
• To correlate structural specialization with junction length and identify potential mechanisms of active zone remodeling.
• To explore the role of synaptic structures in response to environmental stimuli.

Main Methods:

• Analysis of E-PTA stained and osmicated rat occipital cortex tissue from 15-224 days.
• Quantification of synaptic active zone morphology, including specialized regions, curvature, and perforation.
• Microscopic examination of presynaptic terminals with multiple active zones and associated spine apparatus.

Main Results:

• Synaptic active zone specialization increases with junction length during maturation.
• Perforated junctions suggest ongoing addition and differentiation of active zone material.
• The number of multiple active zones increases with maturation, paralleling simple perforated junctions.
• Spine apparatus is frequently observed in perforated terminals, indicating a role in reorganization.
• Junction curvature is predominantly negative, indenting the postsynaptic process.
• Perforated terminals exhibit twice the postsynaptic thickening length of non-perforated terminals, suggesting active zone duplication.
• Evidence suggests terminal splitting as a mechanism for increasing synaptic connections.

Conclusions:

• Synaptic active zone remodeling is an active and ongoing process throughout later development and maturation.
• Active zone duplication and subsequent splitting may be a mechanism for increasing synaptic connections in response to neuronal activity or enriched environments.
• These findings provide insights into the plasticity of neuronal connections and their adaptation to experience.