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Keywords:

  • contrast agent;
  • MEMRI;
  • manganese;
  • brain development;
  • blood–brain barrier;
  • T1 relaxation time

Abstract

Purpose

To measure regional T1 changes in the postnatal rat brain following systemic administration of the contrast agent manganese chloride (MnCl2).

Materials and Methods

MnCl2 (120 mM) was administered intravenously (i.v.) at 1.25 mL/hour to a dose of 175 mg/kg body weight. MRI experiments were performed on anaesthetized animals (32 male Wistar rats, postnatal days (PDs) 11, 16, 21, and 31) at 2.0 T. Regions of interest (ROIs) were drawn in sagittal slices and placed over five brain regions: olfactory bulb, cerebellum, cortex, thalamus, and hypothalamus. The signal intensities of each ROI were measured and fitted to a three-parameter function to estimate T1 values.

Results

In the brains of animals who did not receive the contrast agent (control group), we observed a consistent age-dependent decrease in T1 values. In the brains of manganese-infused animals (manganese group), however, T1 values were significantly lower than in the control group, indicating the uptake of manganese, but no dependence of T1 on age was found.

Conclusion

Our T1 measurements indicate that the relative Mn2+ concentrations are higher in neonates and decrease with brain development. An estimate of the relative cortical concentration of manganese shows a two-fold drop from PD 11 to PD 31. J. Magn. Reson. Imaging 2007. © 2006 Wiley-Liss, Inc.