Abstract
Purpose: :
To compare pentobarbital sodium (PB) and propofol (PF) anesthetics for multifocal electroretinograms (mfERGs) in rhesus macaques.
Methods: :
mfERGs were collected from 4 adult female rhesus macaques anesthetized with either PB or PF in a counterbalanced repeated measures design. All animals were pre-anesthetized with ketamine (10-15 mg/kg IM). PB induction/maintenance levels were 15 mg/kg IV/2-10 mg/kg IV, and for PF, 2-5 mg/kg IV/12-24 mg/kg/h IV, respectively. ERG-jet electrodes were referenced to subdermal electrodes inserted at the ipsilateral outer canthi. Eyes were refracted for the 20-cm viewing distance. A reversing ophthalmoscope was used to align the center of the 241-element unstretched stimulus array and the fovea. Mean luminance was 100 cd/m2. 215-1 m-sequence, 13.3-ms base period, and 1200-Hz signal sampling rate of VERIS Science 4 were used in mfERG response collection. Effects of anesthesia, tested eye and retinal location (ring and quadrant) on the four primary waves for K1 response density amplitude (RDA) and implicit time (IT), and root mean square signal-to-noise ratios (RMS SNR) of the K1 and K2.1 low-frequency and K1 high-frequency components were evaluated by separate analyses of variance.
Results: :
K1 RMS SNR in ring and quadrant analyses was significantly larger (p<0.0005) for PF than PB. For K1 ring and quadrant analyses, PF RDA was significantly larger (30%-50%) than PB RDA for N1, P1 and P2 waves (ring), and for the N2 wave (quadrant). PF IT was significantly prolonged (<1 ms) than PB IT for N1, P1 (ring) and N1 (quadrant) waves while PB IT was significantly prolonged (0.8 ms-4.0 ms) than PF IT for N2 and P2 (ring) and N2 and P2 (quadrant) waves.
Conclusions: :
PF and PB both resulted in robust and replicable mfERGs in rhesus macaques. RDA was generally larger under PF than PB, and N1 and P1 IT were prolonged subtly for PF than PB, but for N2 and P2 IT, PB was more prolonged than PF responses. These response differences likely arise from variable relative effects of the anesthetics on retinal GABAA receptors. Given the advantages of rapid recovery and stable anesthetic plane with continuous IV infusion, PF is an attractive alternative for mfERG testing in rhesus macaques.
Keywords: electroretinography: non-clinical