| ObjectiveTo observe the characteristics of short and long-term synaptic plasticity during critical period of visual development of different rearing condition and age in rats, and analyze how the visual experience and the age affects the transmission characteristics of layer Ⅱ/Ⅲ pyramidal cells.MethodsWistar rats were used, and they were divided into four groups depending on age, P14-P16, P21-P23, P28-P30. Whole-cell voltage clamp recordings were used. The stimulating and recording electrodes were placed in the layer Ⅳ and Ⅱ/Ⅲ of the primary visual cortex respectively. The membrane potential was clamped on-70mV,0mV respectively to separate EPSCs and IPSCs. Paired-pulse ratio, IPSC/EPSC ratio, and long-term synaptic plasticity were seted as the observation indicators; the development features of short and long-term synaptic plasticity of different rearing condition and age groups of layer Ⅱ/Ⅲ pyramidal cells were compared and analyzed. The results were shown as means±SEM. After the homogeneity test for variance, the statistical significance was assessed using t tests or analysis of variance.ResultsIn the critical period of visual development, the differences of PPR of EPSCs in layer Ⅱ/Ⅲ pyramidal neurons of NR rats with different ages were not significant (F=0.972, P=0.423, one-way ANOVA), but that of IPSCs’ were significant (F=4.511, P=0.015), and the PPR of IPSCs declined mainly during P16and P21; The PPR of EPSCs and IPSCs between P14-16and P21-23age group in NR rats was significantly different (P=0.033;P=0.013); The IPSC/EPSC ratio of NR rats increased slightly after eye open, but there were no significant difference among age groups (F=0.363, P=0.781). The PPR of EPSCs and IPSCs, and the IPSC/EPSC ratio of DR rats did not change obviously with age increasing, Rearing conditions (F=0.043, P=0.837) and aging (F=0.940, P=0.427) did not affected the PPR of EPSCs obviously, while impacted that of IPSCs significantly (F=8.289, P=0.006; F=2.841, P=0.048, two-way ANOVA); When accepted normal rearing conditions, the short-term synaptic plasticity was no significant different between30DxN and P35-P37DR rats (PPR of EPSCs:P=0.183; PPR of IPSCs:P=0.342).The long-term synaptic plasticity in layer Ⅱ/Ⅲ pyramidal neurons of NR rats increased before P21-P23and then declined, there was a significant difference among various rearing conditions (F=4.978, P=0.008, one-way ANOVA), and that of DR rats did not change much with age increasing; the statistical results by two-way ANOVA showed that rearing conditions (F=21.065, P=3.108E-5) but not aging (F=1.590, P=0.208) affected the long-term synaptic plasticity in layer Ⅱ/Ⅲ pyramidal neurons; Compared with P35-P37DR rats, the long-term synaptic plasticity of30DxN rats increased slightly, but the difference was not significant (P=0.069).ConclusionsIn the critical period of visual development, the PPR of IPSCs in layer Ⅱ/Ⅲ pyramidal neurons of NR rats plays a more important role, which changes mainly during one week after eye open. The inhibitory components increase relatively during the critical period of visual development.The PPR of EPSCs and IPSCs, and the IPSC/EPSC ratio in layer Ⅱ/Ⅲ pyramidal neurons of DR changes little during the critical period of visual development, and statistical analysis showed that changes in the above indicators of NR rats is mainly caused by the visual experience; Dark rearing can postpone the critical period of visual development, but the short-term synaptic plasticity of the delayed critical period was slightly different to that of NR rats.The long-term synaptic plasticity of DR rats did not change obviously with age, keeping in a stable level, and that of DR rats increases mainly during one week after eye open, indicating that the changes of long-term synaptic plasticity of NR rats are impacted mainly by visual experiences; the long-term synaptic plasticity of layer Ⅱ/Ⅲ pyramidal neurons in the primary visual cortex of DR rats is postponed, the delayed synaptic plasticity is weaker than that of NR rats. |
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