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. 2022 Feb;10(3):141.
doi: 10.21037/atm-21-6723.

Assessing the impact of monocular deprivation on visual evoked potentials, behavior, and visual plasticity in juvenile mice

Suzhen Ding  1 , Chunxian Yang  2 , Hefei Zhu  1 , Shaomin Li  3 , Lan Li  1
Affiliations

Assessing the impact of monocular deprivation on visual evoked potentials, behavior, and visual plasticity in juvenile mice

Suzhen Ding et al. Ann Transl Med. 2022 Feb.

Abstract

Background: The physiological mechanisms which underlie amblyopia are predicted using animal models which assess the impact of amblyogenic factors on visual function. This study used monocular-deprived mice as an amblyopic model to assess visual function by flash visual evoked potentials (fVEP), behavioral assessment, and visual plasticity.

Methods: A total of 294 C57BL/6J mice (both genders) were used in this study. The mice were divided into the normal control (NC) group and monocular deprivation (MD) group. After mice were anesthetized with pentobarbital, fVEP was recorded. Long-term potentiation (LTP) was recorded from primary visual cortex slices. Behavioral assessment of visual function was performed using a visual water trapezoidal-shaped pool with a release chute, a hidden platform, and a middle divider.

Results: All fVEP results showed that N1 waves and P2 waves were repeatable and N1-P2 amplitude was the most stable indicator. The amplitude of N1-P2 of MD eyes was significantly lower than that of non-deprived eyes or NC eyes. LTP failed to be induced in the visual cortex V1 area corresponding to deprived eyes in the MD group but could be induced successfully in the visual cortex V1 area corresponding to non-deprived eyes in the MD group. Behavioral vision testing also showed a longer time to reach the platform in MD mice compared to NC mice. The correlation coefficient suggested that LTP is the better indicator for visual impairment.

Conclusions: The fVEP can be utilized as an index of amblyopic changes in mice, which correlates well with behavioral results.

Keywords: Visual evoked potential (VEP); long-term potentiation (LTP); mice; monocular deprivation (MD); visual water maze.

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Conflict of interest statement

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://atm.amegroups.com/article/view/10.21037/atm-21-6723/coif). The authors have no conflicts of interest to declare.

Figures

Figure 1
Figure 1
Schematic diagrams of the methods used in this study. (A) Flash VEP recording. (B) LTP recording in visual cortex slices with a stimulation electrode (S) placed in layer IV of the visual cortex (V1) area and a recording electrode (R) placed in layer II/III of the visual cortex to record the fEPSP. (C) Visual behavioral test box. a, visible sign (grating); b: hidden platform; c: divider; d: release chute. VEP, visual evoked potential; LTP, long-term potentiation; fEPSP, field excitatory postsynaptic potential.
Figure 2
Figure 2
Flash VEP response from NC mice. (A) Representative fVEP response recorded from a normal mouse. (B) Summary of the latency of the N1 wave from a total of 540 eyes (orange) and each eye (right in black, left in red). (C) Summary of the latency of the P2 wave from a total of 540 eyes (orange) and each eye (right in black, left in red). (D) Summary of the peak-to-peak amplitudes of the N1–P2 wave from a total 540 eyes (orange) and each eye (right in black, left in red). VEP, visual evoked potential; NC, normal control; fVEP, flash visual evoked potentials.
Figure 3
Figure 3
Changes in fVEP after MD for 7 days. (A) The latency of the N1 wave before eyelid suture (day 1) compared to that after suture and reopening of the eye (day 8). (B) The latency of the P2 wave before eyelid suture (day 1) compared to that after suture and reopening of the eye (day 8). (C) The amplitudes of the N1–P2 wave before eyelid suture (day 1) compared to that after suture and reopening of the eye (day 8). The black bar represents non-deprived eyes and the red bar represents deprived eyes (*, P<0.05; **, P<0.01). fVEP, flash visual evoked potentials; MD, monocular deprivation.
Figure 4
Figure 4
MD impaired LTP in the primary visual cortex slices. (A) The input-output response was generated by stimulating layer IV and recording in layer II/III (n=5 in each group). (B) Summary of the paired-pulse ratio against different interstimulation intervals. (C) Time course of LTP induced by 2 trains of 100 Hz stimuli in the visual cortex slices from NC mice (n=7 slices), the corresponding cortex to the deprived eye (n=11 slices), and the corresponding cortex to the non-deprived eye (n=9 slices). (D) Quantitative analysis of fEPSP potentiation was determined at a mean of 40 minutes after HFS (**, P<0.01). MD, monocular deprivation; LTP, long-term potentiation; NC, normal control; fEPSP, field excitatory postsynaptic potential; HFS, high-frequency stimulation.
Figure 5
Figure 5
In the visual water tasks, the average times and success rates for 15 mice to reach the escape platform were tested over 7 days. (A) The time to reach the platform on each of the 7 days of testing in the visual behavioral task. (B) The time to reach the platform on day 10 with visible signs (red) and day 11 without visible signs in the visual behavioral task. (C) The success rates (direct from the release chute to the platform) on each of the 7 days of testing in the visual behavioral task. (D) The success rates on day 10 with visible signs (red) and on day 11 without visible signs in the visual behavioral task (*, P<0.05; **, P<0.01).
Figure 6
Figure 6
MD prolongs the time to arrive at the platform. (A) Representative swim paths on day 1 (left) and day 7 (right) from a NC mouse. (B) Representative swim paths on day 1 (left) and day 7 (right) from an MD mouse. (C) The time to reach the platform for NC mice (black, n=17) and MD mice (n=17, red) on each of the 7 days of testing in the visual behavioral task. (D) The time to reach the platform on day 10 with grating (left panel) and day 11 without grating (right panel) in both groups in the visual behavioral task. (E) The success rates on day 10 with grating (left panel) and on day 11 without grating (right panel) in the visual behavioral task. MD, monocular deprivation; NC, normal control.
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