title: Activity-induced manganese-dependent MRI (AIM-MRI) and functional MRI in awake rabbits during somatosensory stimulation.
abstract: Activity-induced manganese-dependent MRI (AIM-MRI) is a powerful tool to track system-wide neural activity using high resolution, quantitative T1-weighted MRI in animal models and has significant advantages for investigating neural activity over other modalities including BOLD fMRI. With AIM-MRI, Mn(2+) ions enter neurons via voltage-gated calcium channels preferentially active during the time of experimental exposure. A broad range of AIM-MRI studies using different species studying different phenomena have been performed, but few of these studies provide a systematic evaluation of the factors influencing the detection of Mn(2+) such as dosage and the temporal characteristics of Mn(2+) uptake. We identified an optimal dose of Mn(2+) (25 mg/kg, s.c.) in order to characterize the time-course of Mn(2+) accumulation in active neural regions in the rabbit. T1-weighted MRI and functional MRI were collected 0-3, 6-9, and 24-27 h post-Mn(2+) injection while the vibrissae on the right side were vibrated. Significant BOLD activation in the left somatosensory (SS) cortex and left ventral posteromedial (VPM) thalamic nucleus was detected during whisker vibration. T1-weighted signal intensities were extracted from these regions, their corresponding contralateral regions and the visual cortex (to serve as controls). A significant elevation in T1-weighted signal intensity in the left SS cortex (relative to right) was evident 6-9 and 24-27 h post-Mn(2+) injection while the left VPM thalamus showed a significant enhancement (relative to the right) only during the 24-27 h session. Visual cortex showed no hemispheric difference at any timepoint. Our results suggest that studies employing AIM-MRI would benefit by conducting experimental manipulations 6-24 h after subcutaneous MnCl2 injections to optimize the concentration of contrast agent in the regions active during the exposure.
authors.affiliation: Department of Physiology, Feinberg School of Medicine, Northwestern University, 303 E. Chicago Avenue, Ward Building 7-140, Chicago, IL 60611, USA. Electronic address: mp.schroeder@u.northwestern.edu.
authors.forename: Matthew P
authors.initials: MP
authors.lastname: Schroeder
authors.affiliation: Department of Physiology, Feinberg School of Medicine, Northwestern University, 303 E. Chicago Avenue, Ward Building 7-140, Chicago, IL 60611, USA. Electronic address: cweiss@northwestern.edu.
authors.forename: Craig
authors.initials: C
authors.lastname: Weiss
authors.affiliation: Department of Radiology, Feinberg School of Medicine, Northwestern University, 737 North Michigan Avenue, Suite 1600, Chicago, IL 60611, USA. Electronic address: d-procissi@northwestern.edu.
authors.forename: Daniel
authors.initials: D
authors.lastname: Procissi
authors.affiliation: Department of Radiology, Feinberg School of Medicine, Northwestern University, 737 North Michigan Avenue, Suite 1600, Chicago, IL 60611, USA; Department of Psychiatry and Behavioral Sciences, Feinberg School of Medicine, Northwestern University, 710 N. Lake Shore Drive, Abbott Hall 1322, Chicago, IL 60611, USA. Electronic address: leiwang1@northwestern.edu.
authors.forename: Lei
authors.initials: L
authors.lastname: Wang
authors.affiliation: Department of Physiology, Feinberg School of Medicine, Northwestern University, 303 E. Chicago Avenue, Ward Building 7-140, Chicago, IL 60611, USA. Electronic address: jdisterhoft@northwestern.edu.
authors.forename: John F
authors.initials: JF
authors.lastname: Disterhoft
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000502:physiology; D002712:Chlorides / Q000008:administration & dosage / Q000378:metabolism*; D005260:Female; D007089:Image Enhancement / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D017895:Manganese Compounds / Q000008:administration & dosage / Q000378:metabolism*; D009043:Motor Activity / Q000502:physiology*; D011817:Rabbits; D013003:Somatosensory Cortex / Q000378:metabolism*; D020651:Ventral Thalamic Nuclei / Q000378:metabolism*; D014738:Vibrissae / Q000502:physiology*
chemical_list: D002712:Chlorides; D017895:Manganese Compounds; C025340:manganese chloride
keywords: Activity-induced; Awake animal MRI; Functional magnetic resonance imaging; Manganese-enhanced MRI; Rabbit; Somatosensory