Pharmacokinetically optimized anesthesia enables long-term functional ultrasound imaging in the cat visual cortex

Functional ultrasound imaging (fUSI) gauges cerebral blood-volume changes, thus anesthesia protocols developed for blood-oxygen-level-dependent functional magnetic resonance imaging (BOLD fMRI) may not sustain its signal. Researchers evaluated three fMRI-derived anesthesia regimens for visually evoked fUSI in the cat visual cortex.

Isoflurane-ketamine-medetomidine generated the most robust and consistent responses, however, the customary intramuscular medetomidine bolus inhibited the signal in a single sensitive cat. By applying pharmacokinetic modeling, the bolus was replaced with controlled intravenous dosing, thereby restoring the visual response while preserving physiological stability.

This weight-based regimen yielded strong responses across other animals as well. In a session-by-session comparison, response intensity remained constant even after more than three hours. Over 464 recordings from 51 sessions conducted in three cats spanning up to 23 months, fUSI exhibited no temporal drift. Although visually evoked activation remained distinct from a small awake dataset, equivalence was not confirmed.

Consequently, PK-guided regulation of medetomidine exposure allows for consistent, repeated fUSI of the cat visual cortex over extended periods.