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Nitin Chitranshi, Yuyi You, Vivek Kumar Gupta, Alexander Klistorner, Stuart L Graham, ; Effects of isoflurane on the visual evoked potentials in rats. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):468.
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Isofluorane has been widely used for recovery experiments, including visual electrophysiological studies, in rodents. However, it can potentially affect visual evoked potential (VEP) recordings due to GABAergic activity associated with it and subsequent burst suppression on the electroencephalogram response. This study aims to investigate the effects of isoflurane on VEP amplitude and latency in rats.
VEPs of Sprague-Dawley (SD) rats (n=9) were recorded via implanted skull screw electrode on one randomly selected eye under different levels of isoflurane-induced anaesthesia. Recordings were repeated three times to evaluate the intersession repeatability. . The latencies of P1, N1 and the amplitude of each component were measured and analysed. The light pulse was generated using mini-Ganzfeld stimulator (3 cd.s/m2).
An increase in isoflurane concentration causes significant (p<0.005) prolongation in N1 and P1latencies as well as reduction in the VEP amplitudes (Figure 1). The latencies (ms) recorded at 1.5%, 2.0%, 2.5% and 3.0% of isoflurane concentrations were 31.4 + 0.76, 33.2 + 1.2, 34.5 + 1.4, and 35.1 + 1.2 for N1 and 40.9 + 1.1, 43.9 + 1.2, 45.7 + 1.2, and 47.4 + 1.3 for P1 respectively. The N1-P1 amplitude (µV) recorded at 1.5%, 2.0%, 2.5% and 3.0% isofluorane anaesthesia was 29.7 + 3.9, 25.3 + 4.1, 19.6 + 2.4 and 14.2 + 3.2 respectively.
These studies suggest that the use isofluorane as an anaesthetic agent can significantly prolong VEP latency and reduce its amplitude in a dose-dependent manner. The effects on latency and amplitude measurement need to be carefully evaluated when VEPs are recorded under isofluorane anaesthesia. It is recommended that alternative methods of anaesthesia such as use of ketamine should be considered in cortical evoked potential studies.
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