Physiological characterization of a robust survival rodent fMRI method

Area of Science:

• Neuroscience
• Physiology
• Medical Imaging

Background:

• Anesthesia choice is critical for preclinical functional MRI (fMRI) to ensure normal autonomic function.
• Previous studies suggest low-dose dexmedetomidine and isoflurane offer stable fMRI measurements, but potential confounding physiological effects of dexmedetomidine require investigation.

Purpose of the Study:

• To systematically characterize physiological conditions during fMRI under a low-dose dexmedetomidine and isoflurane regimen.
• To evaluate the integrity of neurovascular coupling and brain network function over time with this anesthetic protocol.

Main Methods:

• Rats were administered a continuous low dose of dexmedetomidine with spontaneously-inhaled low-dose isoflurane.
• Task-evoked (somatosensory stimulation) and resting-state fMRI were acquired across three time windows (0-30min, 30-90min, 90-150min).
• Autonomic physiological parameters were monitored throughout the fMRI sessions.

Main Results:

• Both evoked BOLD responses and resting-state fMRI signals remained stable between 90-150 minutes post-anesthetic initiation.
• Autonomic physiological parameters were maintained within near-normal ranges during the 90-150min time window.
• The anesthetic regimen minimally disturbed brain network functions, allowing identification of the rat default mode network.

Conclusions:

• A combination of low-dose, continuously infused dexmedetomidine and spontaneously-inhaled low-dose isoflurane is a viable anesthetic option for longitudinal rodent fMRI studies.
• This protocol supports stable neuroimaging and physiological conditions, crucial for reliable repeated measurements in preclinical research.
• The findings provide a foundation for optimizing anesthetic strategies in long-term fMRI investigations.