Kevin C. Chan1,2, Joe S. Cheng2,3, Ed X. Wu1,2
1Laboratory of Biomedical Imaging & Signal Processing, the University of Hong Kong, Pokfulam, Hong Kong, China, People's Republic of; 2Department of Electrical & Electronic Engineering, the University of Hong Kong, Pokfulam, Hong Kong, China, People's Republic of; 3Laboratory of Biomedical Imaging & Signal Processing, the University of Hong Kong,, Pokfulam, Hong Kong, China, People's Republic of
This study explores the capability of high-resolution Mn-enhanced MRI (MEMRI) for in vivo assessment of the retinal projections in the superior colliculus (SC) and lateral geniculate nucleus (LGN) of early postnatal rat brains before eyelid opening. Eight hours (Hr8) after intravitreal Mn2+ injection into the right eye, significant increases in T1-weighted signal intensities (T1WSI) were observed in the left SC and LGN of the neonatal rats at postnatal days (P) 1, 5, and 10, and the adult rats and mice at P60. While the T1WSI of left SC and LGN continued to increase in the P60 rats, or remained the same in the P60 mice, the T1WSI of left SC and LGN dropped significantly in the neonatal rats at 1 day after Mn2+ administration (D1). A small but significant increase in T1WSI could also be observed in the right SC of neonatal brains at Hr8, as well as the adult mice at D1. These results suggested the high sensitivity of MEMRI for measuring retinotopic changes along both ipsilateral and contralateral visual pathways in normal development, disease, plasticity and therapy longitudinally in the neonatal brains in future studies.