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Vet Ophthalmol. 2018 May;21(3):290-297. doi: 10.1111/vop.12507. Epub 2017 Nov 17.

Long-term anesthetic protocol in rats: feasibility in electrophysiology studies in visual prosthesis.

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Graduate School of Biomedical Engineering, UNSW, Sydney, NSW, 2052, Australia.
Division of Neuroscience, University Pablo de Olavide, Sevilla, 41013, Spain.
Sydney Imaging Core Research Facility, The University of Sydney, NSW, 2006, Australia.
School of Medicine, The University of Western Sydney, Sydney, NSW, Australia.
School of Medical Science, UNSW, Sydney, NSW, 2052, Australia.
Sydney Medical School, The University of Sydney, NSW, 2006, Australia.
Faculty of Engineering and Information Technologies, The University of Sydney, NSW, 2006, Australia.


Electrical stimulation of excitable cells provides therapeutic benefits for a variety of medical conditions, including restoration of partial vision to those blinded via some types of retinal degeneration. To improve visual percepts elicited by the current technology, researchers are conducting acute electrophysiology experiments, mainly in cats. However, the rat can provide a model of a range of retinal diseases and possesses a sufficiently large eye to be used in this field. This article presents a long-term anesthetic protocol to enable electrophysiology experiments to further the development of visual prostheses. Six Long-Evans rats (aged between 14 and 16 weeks) were included in this study. Surgical anesthesia was maintained for more than 15 h by combining constant intravenous infusion of ketamine (24.0-34.5 mg/kg/h), xylazine (0.9-1.2 mg/kg/h), and inhaled isoflurane in oxygen (<0.5%). Overall heart rate, respiratory rate, and body temperature remained between 187-233 beats/min, 45-58 breaths/min, and 36-38 °C, respectively. Neural responses to 200-ms light pulses were recorded from the superior colliculus using a 32-channel neural probe at the beginning and before termination of the experiment. Robust responses were recorded from distinct functional types of retinal pathways. In addition, a platinum electrode was implanted in the retrobulbar space. The retina was electrically stimulated, and the activation threshold was determined to be 5.24 ± 0.24 μC/cm2 . This protocol may be used not only in the field of visual prosthesis research, but in other research areas requiring longer term acute experiments.


anaesthesia; bionic vision; electrical stimulation; retinal prosthesis; visual neuroscience; vitals monitoring

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