Epilepsy Research 67 (2005) 133–141 Small animal positron emission tomography during vagus nerve stimulation in rats: A pilot study Stefanie Dedeurwaerdere a,∗ , Bart Cornelissen b,c , Koen Van Laere d , Kristl Vonck a , Eric Achten e , Guido Slegers b , Paul Boon a a Laboratory for Clinical and Experimental Neurophysiology, Department of Neurology, Ghent University Hospital, Ghent, Belgium b Laboratory of Radiopharmacy, Ghent University, Ghent, Belgium c Laboratory for Molecular Imaging and Targeted Radiotherapy, University of Toronto, Toronto, Ont., Canada d Division of Nuclear Medicine, UZ Gasthuisberg, KU Leuven, Leuven, Belgium e Department of Radiology, Ghent University Hospital, Ghent, Belgium Received 22 August 2005; received in revised form 23 September 2005; accepted 24 September 2005 Abstract Vagus nerve stimulation (VNS) is an effective neurophysiological treatment for patients with refractory epilepsy, however, the mechanism of action remains unclear. Small animal positron emission tomography (PET) permits the monitoring of biochemical processes during multiple scans in the same animal. The aim of this pilot study was to explore the potential of 2-[ 18 F]-fluoro-2- deoxy-d-glucose (FDG)-PET to investigate the effect of acute and chronic VNS on glucose metabolism in the rat brain. One week after EEG and VNS electrode implantation, a baseline FDG-PET scan was acquired during which animals were not stimulated. Secondly, scans were taken after first activation of the VNS electrode (acute VNS) and after one week of continuous VNS (chronic VNS). On the same time points, images were obtained in a control group. After acquisition, PET images were manually fused with MRI data. Normalized brain activities and left/right activity ratios of different brain structures were compared between control measurements and VNS group. During acute VNS, glucose metabolism was significantly decreased in the left hippocampus (P < 0.05). Significant increases were found in both olfactory bulbs (P < 0.05). During chronic VNS, a significant decrease in left/right ratio in the striatum (P < 0.05) was found. Acute and chronic VNS induced changes in glucose metabolism in regions important for seizure control (hippocampus and striatum). Our results promote further brain research on VNS using small animal PET in rats. © 2005 Elsevier B.V. All rights reserved. Keywords: Small animal positron emission tomography (PET); Vagus nerve stimulation (VNS); Micro-PET; Mechanism of action; Rat; Epilepsy ∗ Corresponding author. Tel.: +32 9 2403355; fax: +32 9 2403360. E-mail address: Stefanie.Dedeurwaerdere@hotmail.com (S. Dedeurwaerdere). 0920-1211/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.eplepsyres.2005.09.008