Metabolic Differences in Neuroimaging with [¹⁸F]FDG in Rats Under Isoflurane and Hypnorm-Dormicum

Area of Science:

• Neuroscience
• Radiochemistry
• Pharmacology

Background:

• Anesthesia profoundly influences brain activity and metabolism.
• Accurate interpretation of preclinical positron emission tomography (PET) neuroimaging relies on understanding anesthetic effects.
• Common rodent anesthetics, isoflurane and Hypnorm-Dormicum, may differentially affect neuroimaging outcomes.

Purpose of the Study:

• To investigate the impact of isoflurane versus Hypnorm-Dormicum anesthesia on [18F]fluorodeoxyglucose ([18F]FDG) uptake in the rat brain.
• To compare whole-brain standard uptake values (SUV) and regional brain metabolism under different anesthetic conditions.
• To assess the implications of anesthetic choice for preclinical PET neuroimaging interpretation.

Main Methods:

• Adult female Sprague Dawley rats were randomized into isoflurane or Hypnorm-Dormicum anesthesia groups.
• Dynamic [18F]FDG PET scans were performed on all subjects.
• Whole-brain SUV and voxel-based analysis were conducted to quantify [18F]FDG uptake.

Main Results:

• Rats under isoflurane anesthesia exhibited a 38% lower brain [18F]FDG SUV compared to the Hypnorm-Dormicum group after 40 minutes (p = 0.0008).
• Voxel-based analysis confirmed reduced [18F]FDG uptake in isoflurane-anesthetized rats, predominantly in cortical areas.
• Minor increases in [18F]FDG uptake were observed in the midbrain and cerebellum in the isoflurane group.

Conclusions:

• Anesthetic choice significantly alters brain [18F]FDG uptake, likely due to variations in metabolic activity.
• Isoflurane anesthesia leads to decreased glucose analog uptake in key brain regions compared to Hypnorm-Dormicum.
• These findings highlight the critical need to consider anesthetic agents when designing and interpreting preclinical rodent PET neuroimaging studies.