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J. M. Harrison; Electroretinogram (ERG) in Mice Anesthetized With Ketamine-Xylazine or Avertin. Invest. Ophthalmol. Vis. Sci. 2008;49(13):2009.
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Ketamine-xylazine (K-X) is the most common anesthetic used in ERG studies of mice. Avertin (Av; tribromoethanol) has a much lower mortality rate than K-X and has been used for decades in transgenics research. The purpose of the study was to compare ERGs of mice anesthetized with K-X or Av and tested under the same conditions.
C57Bl/6 mice were dark adapted for 4 hr, anesthetized with K-X (n=10; 80 and 10 mg/kg) or Av (n=5; 0.3 mg/g), and prepared for testing under dim red illumination. Full-field ERGs were produced in the darkby 7 cd sc s m-2 (St Fl) and 0.023 cd sc s m-2 (St Fl -2.5) flashes. Wide band-pass ERGs (1-1000 Hz) were recorded from the left eye with silver-bonded nylon fibers referred to a subdermal electrode in the lower jaw. ERGs were processed by a finite impulse response filter to yield low (1-55 Hz) and high (55-200 Hz) band-pass filtered ERG. The a- and b-wave amplitudes and b-wave implicit times (IT) were derived from the low band-pass filtered ERGs. The high-band-pass ERGs were rectified and integrated from 0-0.1 s after the flash. The maximum of the integral times 10 yielded the integrated oscillatory potential (OP) amplitudes in microvolt s. The data were compared by a two-tailed Mann-Whitney test .
The means and (sems) are in the table below. The IT of the ERG produced by the St Fl in the Av groupwas significantly shorter and the OP amplitude of the ERG produced by the St Fl in the Av group was significantly greater than the corresponding values in the K-X group.
The a- and b-wave amplitudes of the ERGs produced by moderate and high intensity flashes in dark adapted Av and K-X were not different. The only differences in the two groups were those that suggest a more robust ERG in the Av group. K-X is known to cause bradycardia and reduced mean arterial pressure and cardiac output. The hemodynamic effects of Av are less severe. Given the milder systemic effects, the reduced mortality rate, and the minimal effects of Av on the ERG demonstrated to date, Av can be considered a preferrable alternative to K-X for ERG studies in mice.
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