Effects of Common Anesthetics on Eye Movement and Electroretinogram

• Type of Material: Article
• Authors: Govind Nair, Emory University; Moon Kim, Atlanta Veterans Affairs Medical Center; Tsukasa Nagaoka, Emory University; Darin Olson, Emory University; Peter Martin Thule, Emory University; Machelle T. Pardue, Emory University; Timothy Q. Duong, University of Texas Health Science Center
• Language: English
• Date: 2011-06
• Publisher: Springer Verlag (Germany)
• Publication Version: Author Accepted Manuscript (After Peer Review)
• Copyright Statement: © Springer-Verlag 2011
• Final Published Version (URL): http://www.springerlink.com/content/6ln41146n3774464/
• Title of Journal or Parent Work: Documenta Ophthalmologica
• ISSN: 0012-4486
• Volume: 122
• Issue: 3
• Start Page: 163
• End Page: 176
• Keywords: magnetic resonance imaging; fMRI; ERG; Anesthesia; eye movement

Abstract

High-resolution magnetic resonance imaging (MRI) provides non-invasive images of retinal anatomy, physiology and function with depth-resolved laminar resolution. Eye movement and drift, however, could limit high spatial resolution imaging, and anesthetics that minimize eye movement could significantly attenuate retinal function. The aim of this study was to determine the optimal anesthetic preparations to minimize eye movement and maximize visual-evoked retinal response in rats. Eye movements were examined by imaging of the cornea with a charge-coupled device (CCD) camera under isoflurane, urethane, ketamine/xylazine, and propofol anesthesia at typical dosages in rats. Combination of the paralytic pancuronium bromide with isoflurane or ketamine/xylazine anesthesia was also examined for the eye movement studies. Visual-evoked retinal responses were evaluated using full-field electroretinography (ERG) under isoflurane, ketamine/xylazine, urethane, and ketamine/xylazine + pancuronium anesthesia in rats. The degree of eye movement was ranked as follows (from large to small displacement per unit time): i) 1% isoflurane, ii) 2% isoflurane, iii) propofol, iv) ketamine/xylazine, v) urethane, vi) ketamine/xylazine + pancuronium and vii)1% isoflurane + pancuronium. The ketamine/xylazine groups showed larger dark-adapted ERG a- and b-waves than other anesthetics tested. The isoflurane group showed the shortest b-wave implicit times. Photopic ERGs in the ketamine/xylazine groups showed the largest b-waves with the isoflurane group showing slightly shorter implicit times at the higher flash intensities. Oscillatory potentials revealed an early peak in the isoflurane group compared to ketamine/xylazine and urethane groups. Pancuronium did not affect the a- and b-wave, but did increase oscillatory potential amplitudes. Compared to the other anesthetics tested here, ketamine/xylazine + pancuronium was the best combination to minimize eye movement and maximize retinal function. These findings should set the stage for further development and application of high-resolution functional imaging techniques, such as MRI, to study retinal anatomy, physiology and function in anesthetized rats.