In vivo imaging of neuronal activation and plasticity in the rat brain by high resolution positron emission tomography (microPET)

Abstract

The study of neural repair and neuroplasticity in rodents would be enhanced by the ability to assess neuronal function in vivo. Positron emission tomography (PET) is used to study brain plasticity in humans, but the limited resolution and sensitivity of conventional scanners have generally precluded the use of PET to study neuroplasticity in rodents. We now demonstrate that microPET, a PET scanner developed for use with small animals, can be used to assess metabolic activity in different regions of the conscious rodent brain using [18F]fluorodeoxyglucose (FDG) as the tracer, and to monitor changes in neuronal activity. Limbic seizures result in dramatically elevated metabolic activity in the hippocampus, whereas vibrissal stimulation results in more modest increases in FDG uptake in the contralateral neocortex. We also show that microPET can be used to study lesion-induced plasticity of the brain. Cerebral hemidecortication resulted in diminished relative glucose metabolism in the neostriatum and thalamus ipsilateral to the lesion, with subsequent, significant recovery of metabolic function. These studies demonstrate that microPET can be used for serial assessment of metabolic function of individual, awake rats with a minimal degree of invasiveness, and therefore, has the potential for use in the study of brain disorders and repair.

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“…5A), the latter having a magnitude of activation consistent with that reported for the rat using a similar imaging method (Kornblum et al, 2000). Pioglitazone significantly improved the CGU response in treated APP mice (activation ratio, 1.07 Ϯ 0.01), rendering it comparable with that of wild-type controls (Fig.…”

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“…The image data acquired from microPET were displayed and analyzed by IDL version 5.5 (Research Systems) and ASIPro version 3.2 (Concorde Microsystems) software. FDG-PET images were reconstructed using a posterior-based 3D iterative algorithm (78) and overlaid on MR templates to confirm anatomical location (79). Coronal sections for striatal and cortical measurements represented brain areas between 0 and +1 mm from the bregma, while thalamic measurements were between -2 and -3 mm from the bregma, as estimated by visual inspection of the contralateral side.…”

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“…27 Final images represent the standard uptake value obtained by correcting individually for animal body weight and injected radioactivity dose.…”