title: Sedation agents differentially modulate cortical and subcortical blood oxygenation: evidence from ultra-high field MRI at 17.2 T.
abstract: BACKGROUND
  Sedation agents affect brain hemodynamic and metabolism leading to specific modifications of the cerebral blood oxygenation level. We previously demonstrated that ultra-high field (UHF) MRI detects changes in cortical blood oxygenation following the administration of sedation drugs commonly used in animal research. Here we applied the UHF-MRI method to study clinically relevant sedation drugs for their effects on cortical and subcortical (thalamus, striatum) oxygenation levels.
  
  
  METHODS
  We acquired T2*-weighted images of Sprague-Dawley rat brains at 17.2T in vivo. During each MRI session, rats were first anesthetized with isoflurane, then with a second sedative agent (sevoflurane, propofol, midazolam, medetomidine or ketamine-xylazine) after stopping isoflurane. We computed a T2*-oxygenation-ratio that aimed at estimating cerebral blood oxygenation level for each sedative agent in each region of interest: cortex, hippocampus, thalamus and striatum.
  
  
  RESULTS
  The T2*-oxygenation-ratio was consistent across scan sessions. This ratio was higher with inhalational agents than with intravenous agents. Under sevoflurane and medetomidine, T2*-oxygenation-ratio was homogenous across the brain regions. Intravenous agents (except medetomidine) induced a T2*-oxygenation-ratio imbalance between cortex and subcortical regions: T2*-oxygenation-ratio was higher in the cortex than the subcortical areas under ketamine-xylazine; T2*-oxygenation-ratio was higher in subcortical regions than in the cortex under propofol or midazolam.
  
  
  CONCLUSIONS
  Preclinical UHF MRI is a powerful method to monitor the changes in cerebral blood oxygenation level induced by sedative agents across brain structures. This approach also allows for a classification of sedative agents based on their differential effects on cerebral blood oxygenation level.
authors: NeuroSpin, Commissariat à l'Energie Atomique et aux Energies Alternatives, CEA Saclay, Gif-sur-Yvette, France; Equipe Avenir INSERM Bettencourt Schueller, NeuroSpin, Unité de Recherche en NeuroImagerie Applicative Clinique et Translationnelle (UNIACT), Gif-sur-Yvette, France.
authors: Lynn
authors: L
authors: Uhrig
authors: NeuroSpin, Commissariat à l'Energie Atomique et aux Energies Alternatives, CEA Saclay, Gif-sur-Yvette, France.
authors: Luisa
authors: L
authors: Ciobanu
authors: NeuroSpin, Commissariat à l'Energie Atomique et aux Energies Alternatives, CEA Saclay, Gif-sur-Yvette, France.
authors: Boucif
authors: B
authors: Djemai
authors: NeuroSpin, Commissariat à l'Energie Atomique et aux Energies Alternatives, CEA Saclay, Gif-sur-Yvette, France.
authors: Denis
authors: D
authors: Le Bihan
authors: NeuroSpin, Commissariat à l'Energie Atomique et aux Energies Alternatives, CEA Saclay, Gif-sur-Yvette, France; Equipe Avenir INSERM Bettencourt Schueller, NeuroSpin, Unité de Recherche en NeuroImagerie Applicative Clinique et Translationnelle (UNIACT), Gif-sur-Yvette, France; Department of Neurosurgery, Neuromodulation Unit, Foch Hospital, University of Versailles Saint-Quentin, Suresnes, France.
authors: Béchir
authors: B
authors: Jarraya
mesh_terms: D000818:Animals; D002540:Cerebral Cortex / Q000098:blood supply / Q000187:drug effects*; D006993:Hypnotics and Sedatives / Q000494:pharmacology*; D007649:Ketamine / Q000494:pharmacology; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D020926:Medetomidine / Q000494:pharmacology; D008738:Methyl Ethers / Q000494:pharmacology; D008874:Midazolam / Q000494:pharmacology; D010100:Oxygen / Q000097:blood*; D015742:Propofol / Q000494:pharmacology; D017207:Rats, Sprague-Dawley; D000077149:Sevoflurane; D014991:Xylazine / Q000494:pharmacology
chemical_list: D006993:Hypnotics and Sedatives; D008738:Methyl Ethers; D014991:Xylazine; D000077149:Sevoflurane; D007649:Ketamine; D020926:Medetomidine; D008874:Midazolam; D010100:Oxygen; D015742:Propofol