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Updated: May 27, 2026
Functional Neuroimaging Using Ultrasonic Blood-brain Barrier Disruption and Manganese-enhanced MRI
Published on: July 12, 2012
Effects of manganese injected into rat nostrils: implications for in vivo functional study of olfaction using MEMRI
Benoist Lehallier1, Gérard Coureaud, Yves Maurin
1UR370 QuaPA, INRA, F-63122 Saint-Genès-Champanelle, France.
Abstract:
Manganese-enhanced magnetic resonance imaging (MEMRI) is a powerful tool for visualizing neuronal pathways and mapping brain activity modulation. A potential drawback of MEMRI lies in the toxic effects of manganese (Mn), which also depend on its administration route. The aim of this study was to analyze the effects of Mn doses injected into the nostrils of rats on both olfactory perception and MRI contrast enhancement. For this purpose, doses in the range 0-8 μmol MnCl(2) were tested. Behavioral items were quantified with and without odor stimulation during the first 2 h following Mn injection. The MRI study was performed after 16 h of intermittent olfactory stimulations. Behavioral results showed that, during the early period following Mn administration, spontaneous motor activity was not affected, while odor-related behaviors were dose-dependently reduced. MRI results showed that, in the primary olfactory cortex, contrast was rapidly enhanced for Mn doses up to 0.3 μmol and very slowly above. This dose of 0.3 μmol Mn can thus be taken as the optimal dose for injection into rat nostrils to ensure a reproducible contrast in MRI studies while sparing olfactory perception.
Insights
This study found the optimal manganese dose for rat nasal injections in MRI studies. A 0.3 μmol dose enhances MRI contrast without impairing olfactory perception.
Area of Science:
- Neuroscience
- Biomedical Imaging
- Toxicology
Background:
- Manganese-enhanced magnetic resonance imaging (MEMRI) visualizes neural pathways but carries risks of manganese (Mn) toxicity.
- Mn toxicity is influenced by its administration route, necessitating careful dose optimization.
Purpose of the Study:
- To determine the effects of intranasal manganese chloride (MnCl2) doses on olfactory perception and MRI contrast enhancement in rats.
- To identify an optimal Mn dose for reproducible MRI studies while minimizing toxicity.
Main Methods:
- Rats received intranasal MnCl2 doses ranging from 0-8 μmol.
- Behavioral tests quantified olfactory perception and motor activity within 2 hours post-injection.
- MRI scans were performed after 16 hours of olfactory stimulation to assess contrast enhancement.
Main Results:
- Intranasal Mn administration did not affect spontaneous motor activity.
- Odor-related behaviors were dose-dependently reduced following Mn injection.
- Optimal MRI contrast enhancement in the primary olfactory cortex was achieved with 0.3 μmol MnCl2, with minimal impact on olfactory perception.
Conclusions:
- An intranasal dose of 0.3 μmol MnCl2 is optimal for MEMRI in rats.
- This dose provides reproducible MRI contrast enhancement while preserving olfactory perception.
- Careful dose selection is crucial for balancing MEMRI efficacy and minimizing Mn toxicity.
