Electrophysiological Study Of Visual Nerve In Retinal Degenerative Reep6 Knockout Mice

Retinal degenerative disease will affect the structure and function of the primary visual cortex（V1）,resulting in plastic changes.The degeneration of the structure and function of photoreceptor cells is one of the important reasons for retinal degeneration.A rod-specific receptor enhancer protein subtype（Reep6）has been found to be involved in the intracellular transport of receptors to the plasma membrane.In the mouse model of Reep6 gene deletion(Reep6^-/-),the number of rod cells in the retina decreased gradually,which led to retinal degeneration in the Reep6^-/-model.It is not clear that whether the gradual degeneration of the retina in this model may lead to the changes in tuning curves of V1 neurons respond to visual features.It will contribute the understanding of relationship of eye degeneration with brain degeneration if clarifying the questions.Therefore,we used Reep6^-/-mice and their control groups as animal models to study the changes of V1 neuron’s tuning curves to visual features,and to explore the possible functional remodeling during retinal degeneration period.The retinal degeneration of Reep6^-/-mice were evaluated by the thickness of retina,which was stained by hematoxylin and eosin（HE）and compared in different layers.The outer nuclear layer（ONL）,outer plexiform layer（OPL）,inner nuclear layer（INL）and inner plexiform layer（IPL）in the retina were measured and analyzed,respectively.The spontaneous activity and the tuning curves of single neuron respond to stimulus characteristics（orientation,spatio-temporal frequency,contrast,size）were quantified by extracellular electrophysiological recording.In addition,the gamma rhythm oscillations were quantified and compared between the two kinds of mice.Our studies discovered that:（1）the thickness of ONL and OPL of Reep6^-/-mice gradually decreases as the increasing of age,in contrast,the thickness of INL and IPL do not change;（2）compared with the control group,the V1 neurons of Reep6^-/-mice have much broad bandwidth in orientation tunings,prefer higher temporal frequencies and lower spatial frequency,and have much larger receptive fields（RF）.However,there were no significant differences in the spontaneous activity,contrast tunings and gamma rhythm oscillations between the two kinds of mice.Our results showed:（1）the retinal degeneration of Reep6^-/-mice began at one month of age,and gradually degenerated as the increasing of age;（2）the gradual degeneration of retina of Reep6^-/-mice led to the weakening of the stimulus selectivity of V1 neurons,and V1 nerve loop and function may have been remodeled,which need to be verified by further experiments.The above research has a certain scientific value and significance for the understanding of eye degeneration to the remodeling of brain function.