An animal model of central auditory pathway imaging in the rat brain by high resolution small animal positron emission tomography

Abstract

Conclusions. Our study demonstrated that high resolution animal positron emission tomography (PET) can non-invasively assess the change in glucose metabolism of the central auditory pathway including the inferior colliculus and auditory cortex in the rat. Objectives. The traditional in vitro approach with immunohistochemical staining or autoradiography to assess chronological changes or topographic arrangement of central auditory pathway required sacrificing a large number of animals. Inter-individual difference is also a major concern. Therefore, development of an in vivo animal model using PET imaging would be a rational method to overcome these shortcomings. Materials and methods. Small animal PET scan using 18F-fluorodeoxyglucose (FDG) as a functional marker was performed in rats. Each animal was serially scanned before and after unilateral cochlear ablation, with and without acoustic stimulation. The images were analyzed by the region of interest (ROI) method. Ratios of radioactivity at the inferior colliculus and auditory cortex and a referenced cerebral cortex between bilateral hemispheres were measured. Results. These scans demonstrated several brain structures including the inferior colliculus (IC) and cortex (B). Moreover, unilateral cochlear ablation decreased the radioactivity at contralateral IC and auditory cortex (C) areas. Differences may reach 33% in IC and 27% in C, and average radioactivity ratios were 1.24±0.08 and 1.18±0.07 in selected adjacent sections, respectively.