title: Brain processing of biologically relevant odors in the awake rat, as revealed by manganese-enhanced MRI.
abstract: BACKGROUND
  So far, an overall view of olfactory structures activated by natural biologically relevant odors in the awake rat is not available. Manganese-enhanced MRI (MEMRI) is appropriate for this purpose. While MEMRI has been used for anatomical labeling of olfactory pathways, functional imaging analyses have not yet been performed beyond the olfactory bulb. Here, we have used MEMRI for functional imaging of rat central olfactory structures and for comparing activation maps obtained with odors conveying different biological messages.
  
  
  RESULTS
  Odors of male fox feces and of chocolate flavored cereals were used to stimulate conscious rats previously treated by intranasal instillation of manganese (Mn). MEMRI activation maps showed Mn enhancement all along the primary olfactory cortex. Mn enhancement elicited by male fox feces odor and to a lesser extent that elicited by chocolate odor, differed from that elicited by deodorized air. This result was partly confirmed by c-Fos immunohistochemistry in the piriform cortex.
  
  
  CONCLUSIONS
  By providing an overall image of brain structures activated in awake rats by odorous stimulation, and by showing that Mn enhancement is differently sensitive to different stimulating odors, the present results demonstrate the interest of MEMRI for functional studies of olfaction in the primary olfactory cortex of laboratory small animals, under conditions close to natural perception. Finally, the factors that may cause the variability of the MEMRI signal in response to different odor are discussed.
authors.affiliation: UR QuaPA, INRA, Saint-Genès-Champanelle, France.
authors.forename: Benoist
authors.initials: B
authors.lastname: Lehallier
authors.forename: Olivier
authors.initials: O
authors.lastname: Rampin
authors.forename: Audrey
authors.initials: A
authors.lastname: Saint-Albin
authors.forename: Nathalie
authors.initials: N
authors.lastname: Jérôme
authors.forename: Christian
authors.initials: C
authors.lastname: Ouali
authors.forename: Yves
authors.initials: Y
authors.lastname: Maurin
authors.forename: Jean-Marie
authors.initials: JM
authors.lastname: Bonny
mesh_terms: D000818:Animals; D001921:Brain / Q000502:physiology*; D007089:Image Enhancement; D008279:Magnetic Resonance Imaging; D008297:Male; D008345:Manganese; D009812:Odorants; D009833:Olfactory Pathways / Q000000981:diagnostic imaging / Q000502:physiology; D055696:Olfactory Perception / Q000502:physiology*; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D011877:Radionuclide Imaging; D051381:Rats
chemical_list: D016760:Proto-Oncogene Proteins c-fos; D008345:Manganese