The Trend Of The Resting Membrane Potential Of Pyramidal Neurons Of The Rat Visual Cortex In Different Stages

ObjectiveTo investigate the trend of resting membrane potential of layer Ⅱ/Ⅲ pyramidal neurons in rat visual cortex in dark-rare rats and normal light conditions resting rats of different stages. To compare the differences between dark-rare rats and normal light conditions rearing rats in the trend of resting membrane potential of layer Ⅱ/Ⅲ pyramidal neurons.Methods㎞ormal light conditions rearing rats were divided into five groups:P10-P12d (no eyes group), P14-P16d(before the critical period of visual development group), P19-P21d(the critical period of visual development group), P35-P40d(after the critical period of visual development group), P>60d(adult group). Using the whole cell patch clamp recording technique, combining infrared differential interference contrast(IR-DIC) technique and CCD-Camera system, the resting membrane potential of layer Ⅱ/Ⅲ pyramidal neurons in slices of rat visual cortex were recorded.(2)Dark-rare rats, divided into three groups:P10-P12d (no eyes group) P14-P16d(before the critical period of visual development group), P19-P21d(the critical period of visual development group), the resting membrane potential of layer Ⅱ/Ⅲ pyramidal neurons in slices of rat visual cortex were recorded in the same way, and compared the differences between dark-rare rats and normal light conditions rearing rats in the trend of resting membrane potential of layer Ⅱ/Ⅲ pyramidal neurons.Results1. The Resting membrane potential of light conditions rearing rats were P10-P12d (-45.665±6.848)mv, P14-P16d (-67.174±6.909)mv, P19-P21d (-72.922±5.302)mv, P35～P40d (-77.294±4.361)mv, P>60d (-78.375±3.695)mv. During the visual development of rats, the resting membrane potential of layer Ⅱ/Ⅲ pyramidal neurons became lower and lower (ANOVA, P<0.05). After the critical period of visual development, it was shown a plat form of the resting membrane potential, there were no significant difference between P30-P34d(after the critical period of visual development group) and P>60d(adult group)(ANOVA, P>0.05).2. The Resting membrane potential of dark-rare rats were P10-P12d(-53.147±4.364)mv, P14-P16d (-60.008±8.082)mv, P19～P21d(-58.019±7.698)mv. The Resting membrane potential of P14-P16d was more lower than the P10-P12d’s (ANOVA, P=0.012, P<0.05). There was no no significant difference between p14-16d and p19-21d (ANOVA, P=0.454, P>0.05)3. Compared the resting membrane potential of layer II/III pyramidal neurons between dark-rare rats and normal light conditions rearing rats in P10-P12d, P14-P16d and P19-P21d, the changes in amplitude of normal light conditions rearing rats are larger than rearing rats’s.Conclusions1. Before the end of the critical period of the visual development of normal light conditions resting rats, the resting membrane potential of layer Ⅱ/Ⅲ pyramidal neurons become lower and lower with the increase of days. However,when the critical period of visual development was end, the resting membrane potential of layer Ⅱ/Ⅲ pyramidal neurons reached a level of maturity. The resting membrane potential of layer Ⅱ/Ⅲ pyramidal neurons of dark-rare rats also become lower with the increase of day, but the changes in amplitude was smaller, and in an immature level.2. Compared the resting membrane potential of layer II/III pyramidal neurons between dark-rare rats and normal light conditions rearing rats in P10-P12d, P14-P16d and P19-P21d, the changes in amplitude of normal light conditions rearing rats are larger than rearing rats’s, indicated that the visual development of rats depends on the visual experience.On the early stage of visual system development, in order to improve itself, visual system was sensitive about stimulus outside to form the effectively connections between pyramidal neurons, modify synaptics. When the critical period of visual development ended, the visual system became maturate, and less sensitive about stimulus outside. The resting membrane potential of layer Ⅱ/Ⅲ pyramidal neurons converged, showed a platform. The dark rearing interferenced the process above, layer Ⅱ/Ⅲ pyramidal neurons maintain the immature state.