Effects of manganese injected into rat nostrils: implications for in vivo functional study of olfaction using MEMRI

• Published in: Magnetic resonance imaging Vol. 30; no. 1; pp. 62 - 69
• Main Authors: Lehallier, Benoist, Coureaud, Gérard, Maurin, Yves, Bonny, Jean-Marie
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier Inc 2012; Elsevier
• Subjects: Administration, Intranasal; Animals; Behavior; Behavior, Animal; Behavior, Animal - drug effects; Contrast Media; Contrast Media - toxicity; Dose; Food and Nutrition; Image Enhancement; Image Enhancement - methods; Life Sciences; Magnetic Resonance Imaging; Magnetic Resonance Imaging - methods; Male; Manganese; Manganese - toxicity; MEMRI; Olfaction; Olfactory Bulb; Olfactory Bulb - anatomy & histology; Olfactory Bulb - physiology; Radiology; Rat; Rats; Rats, Wistar; Smell; Smell - physiology; Toxicity; MEMRI; Rat; Toxicity; Olfaction; Behavior; Dose; Manganese; MEMRI Manganese
• ISSN: 0730-725X; 1873-5894
• DOI: 10.1016/j.mri.2011.08.009

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 MnCl2 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.