Volumetric MRI measurements of the tree shrew hippocampus

Protocols suitable for repeated magnetic resonance imaging (MRI) studies of the tree shrew's brain were established. This included the development of (i) a technique for prolonged inhalation anesthesia by endotracheal intubat ion; (ii) a reproducible fixation of the animal's head in a stereotaxic fra me and finally (iii) the set-up of the hardware (rf coil) and software (MRI sequences) of the MRI system. The endotracheal intubation as well as the r epeated and prolonged anesthesia showed no complications. The in vivo measu rements of the tree shrew's hippocampal formation revealed a high reproduci bility. Right and left hippocampal volume was determined as 85.2 mm(3) +/- 8% and 87.4 mm(3) +/- 10%, respectively. The utility of MRI in delineating alterations in brain anatomy was demonstrated in three animals receiving co rtisol via the drinking water (5 mg/animal/day). After a 4-week treatment, in two of the three tree shrews a reduction in hippocampal volume was obser ved. Thus, the MRI protocols used here allow for repeated and non-invasive measurements of changes in hippocampal anatomy within the same animal and t o monitor the temporal dynamics of structural alterations within this brain structure. (C) 1999 Elsevier Science B.V. All rights reserved.