Abstract
It has been of interest whether and when the rearrangement of neuronal circuits can be induced after projection patterns are formed during development. Earlier studies using cats reported that the rearrangement of retinogeniculate projections could be induced even after eye-specific segregation has occurred, but detailed and quantitative characterization of this rearrangement has been lacking. Here we delineate the structural changes of retinogeniculate projections in the C57BL/6 mouse in response to monocular enucleation (ME) after eye-specific segregation. When ME was performed after eye-specific segregation, rearrangement of retinogeniculate axons in the dorsal lateral geniculate nucleus (dLGN) was observed within 5 days. Although this rearrangement was observed both along the dorsomedial-ventrolateral and outer-inner axes in the dLGN, it occurred more rapidly along the outer-inner axis. We also examined the critical period for this rearrangement and found that the rearrangement became almost absent by the beginning of the critical period for ocular dominance plasticity in the primary visual cortex. Taken together, our findings serve as a framework for the assessment of phenotypes of genetically altered mouse strains as well as provide insights into the mechanisms underlying the rearrangement of retinogeniculate projections.
Highlights
Retinogeniculate projections have been widely used for investigating the mechanisms underlying the initial formation and refinement of neuronal circuits during development [1,2,3,4,5,6,7]
Because previous studies showed that axonal rearrangement is more robust in younger animals than in older animals in other sensory systems [24,25], we performed monocular enucleation (ME) on mouse pups at postnatal day 10 (P10), when the eyespecific projection patterns of retinal ganglion cell (RGC) axons are mostly formed in the dorsal lateral geniculate nucleus (dLGN) [10,12]
We have shown that ME after eye-specific segregation induces the rearrangement of retinogeniculate projections in the mouse dLGN
Summary
Retinogeniculate projections have been widely used for investigating the mechanisms underlying the initial formation and refinement of neuronal circuits during development [1,2,3,4,5,6,7]. Once eye-specific patterns of RGC axons are formed, they are relatively stable thereafter [8,9,10,12] It has been of great interest whether and when the rearrangement of neuronal circuits can be induced after the initial formation and refinement of neuronal circuits occur during development [13,14,15]. Because genetically altered mice are commonly used for investigating molecular mechanisms, detailed and quantitative information about ME-induced rearrangement in mice would be extremely valuable. These points prompted us to examine ME-induced anatomical rearrangement in mice quantitatively. In contrast to earlier studies using cats, previous reports using rats showed that ME after eye-specific segregation did not alter the distribution patterns of RGC axons in the dLGN [19,20]
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