(18F)FDG-PET brain imaging during the micturition cycle in rats detects regions involved in bladder afferent signalling

BACKGROUND: This feasibility study established an experimental protocol to evaluate brain activation patterns using fluorodeoxyglucose positron emission tomography ((18F)FDG-PET) during volume-induced voiding and isovolumetric bladder contractions in rats. METHODS: Female Sprague-Dawley rats were anaesthetized with urethane and underwent either volume-induced voiding cystometry or isovolumetric cystometry and simultaneous functional PET brain imaging after injection of (18F)FDG in the tail vein. Brain glucose metabolism in both groups was compared to their respective control conditions (empty bladder). Relative glucose metabolism images were anatomically standardized to Paxinos space and analysed voxel-wise using Statistical Parametric Mapping 12 (SPM12). RESULTS: During volume-induced voiding, glucose hypermetabolism was observed in the insular cortex while uptake was decreased in a cerebellar cluster and the dorsal midbrain. Relative glucose metabolism during isovolumetric bladder contractions increased in the insular and cingulate cortices and decreased in the cerebellum. CONCLUSIONS: Our findings demonstrate that volume-induced voiding as well as isovolumetric bladder contractions in rats provokes changes in brain metabolism, including activation of the insular and cingulate cortices, which is consistent with their role in the mapping of bladder afferent activity. These findings are in line with human studies. Our results provide a basis for further research into the brain control of the lower urinary tract in small laboratory animals.