Effect of Animal Condition and Fluvoxamine on the Result of [ 18F]N-3-Fluoropropyl-2β-carbomethoxy-3β-(4-iodophenyl) Nortropane ([ 18F]FP-CIT) PET Study in Mice

Abstract

PET (positron emission tomography) is a noninvasive imaging technique, visualizing biological aspects in vivo. In animal models, the result of PET study can be affected more prominently than in humans by the animal conditions or drug pretreatment. We assessed the effects of anesthesia, body temperature, and pretreatment with selective serotonin reuptake inhibitor on the results of [ 18F]N-3-fluoropropyl-2β-carbomethoxy-3β-(4-iodophenyl) nortropane ([ 18F]FP-CIT) PET in mice. Methods: [ 18F]FP-CIT PET of C57BL/6 mice was performed in three different conditions: (1) anesthesia (isoflurane) with active warming (38°C) as a reference; (2) no anesthesia or warming; (3) anesthesia without warming at room temperature. Additional groups of mice pretreated with escalating doses of fluvoxamine (5, 20, 40, 80 mg/kg) were imaged in condition (1). The time activity curve and standardized uptake value of the striatum, cerebral cortex, and bone were compared among these conditions. Results: In all conditions, radioactivities of the striatum and cortex tended to form a plateau after rapid uptake and washout, but that of bone tended to increase gradually. When anesthetized without any warming, all the mice developed hypothermia and showed reduced bone uptake with slightly increased striatal and cortical uptakes compared to the reference condition. In conditions without anesthesia, striatal and cortical uptakes were reduced, whereas the bone uptake showed no change. Pretreatment with fluvoxamine increased the striatal uptake and striatal specific to cortical non-specific uptake ratio, whereas the bone uptake was reduced. Conclusion: Anesthesia, body temperature, and fluvoxamine affect the result of [ 18F]FP-CIT PET in mice by altering striatal and bone uptakes.