Comparison of α-chloralose, medetomidine and isoflurane anesthesia for functional connectivity mapping in the rat

Williams, Kathleen A.; Magnuson, Matthew; Majeed, Waqas; LaConte, Stephen M.; Peltier, Scott J.; Hu, Xiaoping; Keilholz, Shella D.

doi:10.1016/j.mri.2010.03.007

« Previous Next »Magnetic Resonance Imaging
Volume 28, Issue 7 , Pages 995-1003, September 2010

Comparison of α-chloralose, medetomidine and isoflurane anesthesia for functional connectivity mapping in the rat

Kathleen A. Williams
- Department of Radiology, Center for Biomedical Imaging, New York University School of Medicine, New York, NY 10012, USA
Matthew Magnuson
- Wallace H. Coulter Department of Biomedical Engineering, Emory University/Georgia Institute of Technology, Atlanta, GA 30322, USA
Waqas Majeed
- Wallace H. Coulter Department of Biomedical Engineering, Emory University/Georgia Institute of Technology, Atlanta, GA 30322, USA
Stephen M. LaConte
- Department of Neuroscience, Baylor College of Medicine, Houston, TX 76798, USA
Scott J. Peltier
- Functional MRI Laboratory, University of Michigan, Ann Arbor, MI 48109, USA
Xiaoping Hu
- Wallace H. Coulter Department of Biomedical Engineering, Emory University/Georgia Institute of Technology, Atlanta, GA 30322, USA
Shella D. Keilholz
- Wallace H. Coulter Department of Biomedical Engineering, Emory University/Georgia Institute of Technology, Atlanta, GA 30322, USA
- Corresponding author. Tel.: +1 404 727 2433; fax: +1 404 727 9873.

Received 17 July 2009; received in revised form 18 January 2010; accepted 11 March 2010. published online 26 April 2010.

Abstract

Functional connectivity measures based upon low-frequency blood-oxygenation-level-dependent functional magnetic resonance imaging (BOLD fMRI) signal fluctuations have become a widely used tool for investigating spontaneous brain activity in humans. Still unknown, however, is the precise relationship between neural activity, the hemodynamic response and fluctuations in the MRI signal. Recent work from several groups had shown that correlated low-frequency fluctuations in the BOLD signal can be detected in the anesthetized rat — a first step toward elucidating this relationship. Building on this preliminary work, through this study, we demonstrate that functional connectivity observed in the rat depends strongly on the type of anesthesia used. Power spectra of spontaneous fluctuations and the cross-correlation-based connectivity maps from rats anesthetized with α-chloralose, medetomidine or isoflurane are presented using a high-temporal-resolution imaging sequence that ensures minimal contamination from physiological noise. The results show less localized correlation in rats anesthetized with isoflurane as compared with rats anesthetized with α-chloralose or medetomidine. These experiments highlight the utility of using different types of anesthesia to explore the fundamental physiological relationships of the BOLD signal and suggest that the mechanisms contributing to functional connectivity involve a complicated relationship between changes in neural activity, neurovascular coupling and vascular reactivity.

Keywords: α-Chloralose, Medetomidine, Isoflurane, BOLD signal, fMRI