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Updated: Mar 15, 2026
In vivo Imaging of Optic Nerve Fiber Integrity by Contrast-Enhanced MRI in Mice
Published on: July 22, 2014
Dose response and time course of manganese-enhanced magnetic resonance imaging for visual pathway tracing in vivo
Wei-Ling Wang1, Hui Xu2, Ying Li3
1Department of Ophthalmology, Beijing Tsinghua Changgung Hospital, Tsinghua University Medical Center, Beijing, China; Department of Ophthalmology, General Hospital of Ningxia Medical University, Yinchuan, Ningxia Hui Autonomous Region, China.
Abstract:
Axonal tracing is useful for detecting optic nerve injury and regeneration, but many commonly used methods cannot be used to observe axoplasmic flow and synaptic transmission in vivo. Manganese (Mn(2+))-enhanced magnetic resonance imaging (MEMRI) can be used for in vivo longitudinal tracing of the visual pathway. Here, we explored the dose response and time course of an intravitreal injection of MnCl2 for tracing the visual pathway in rabbits in vivo using MEMRI. We found that 2 mM MnCl2 enhanced images of the optic nerve but not the lateral geniculate body or superior colliculus, whereas at all other doses tested (5-40 mM), images of the visual pathway from the retina to the contralateral superior colliculus were significantly enhanced. The images were brightest at 24 hours, and then decreased in brightness until the end of the experiment (7 days). No signal enhancement was observed in the visual cortex at any concentration of MnCl2. These results suggest that MEMRI is a viable method for temporospatial tracing of the visual pathway in vivo. Signal enhancement in MEMRI depends on the dose of MnCl2, and the strongest signals appear 24 hours after intravitreal injection.
Insights
Manganese-enhanced MRI (MEMRI) effectively traces the visual pathway in rabbits after intravitreal injection. Optimal signal enhancement for optic nerve imaging occurs 24 hours post-injection.
Area of Science:
- Neuroscience
- Medical Imaging
Background:
- Axonal tracing is crucial for understanding optic nerve function and repair.
- Conventional methods often fail to visualize dynamic processes like axoplasmic flow and synaptic transmission in vivo.
Purpose of the Study:
- To investigate the efficacy of Manganese-enhanced MRI (MEMRI) for in vivo visual pathway tracing.
- To determine the optimal dose and time course for intravitreal Manganese chloride (MnCl2) injection in rabbits.
Main Methods:
- Rabbits received intravitreal injections of varying MnCl2 concentrations (2-40 mM).
- Manganese-enhanced MRI (MEMRI) was used to image the visual pathway longitudinally.
- Image signal intensity was analyzed over a 7-day period.
Main Results:
- Doses from 5-40 mM MnCl2 significantly enhanced images of the visual pathway from retina to superior colliculus.
- 2 mM MnCl2 only enhanced the optic nerve, not downstream structures.
- Maximum signal enhancement was observed at 24 hours post-injection, diminishing by day 7.
- No signal enhancement was detected in the visual cortex.
Conclusions:
- MEMRI is a viable technique for temporospatial tracing of the visual pathway in vivo.
- The dose of MnCl2 and the time elapsed since injection are critical factors for signal enhancement in MEMRI.
