Eye Opening Primes Synaptic Maturation by Enhancing AMPA Receptor-Mediated Transmission and Spinogenesis in the...

Eye opening represents a critical milestone in postnatal visual development, triggering experience-dependent plasticity that refines neural circuits across visual pathways. While synaptic maturation in the thalamocortical system has been extensively studied, how eye opening shapes synaptic development in the superior colliculus (SC) - a major subcortical hub mediating rapid orienting and motion detection - remains poorly understood. Here, we combine electrophysiological, biochemical, and ultrastructural approaches to investigate experience-promoted synaptic development in the mouse SC following eye opening. We show that eye opening enhances spontaneous AMPAR-mediated synaptic transmission, increasing both the frequency and amplitude of currents. This functional potentiation is accompanied by elevated expression of GluR1, GluR2, and the postsynaptic density protein 95. Structural analyses further reveal enlargement of postsynaptic densities, increased presynaptic vesicle number, and elevated dendritic spine density without altering spine subtype distribution. Our findings demonstrate that eye opening primes robust functional and structural maturation of SC synapses through AMPAR-mediated mechanisms, highlighting the SC as a key site of experience-dependent plasticity with distinct developmental mechanisms in the subcortical visual pathway.