CHOLINERGIC FUNCTIONS FOR BRAIN PLASTICITY DURING BIRD SONG LEARNING

一只年轻的雄性斑马雀在一个敏感的时期学习它的歌声。歌曲学习的感觉运动阶段与歌曲控制核团RA的发育密切相关，RA接受来自另外两个歌曲控制核团的输入。我们先前发现，在歌曲学习的敏感期，当RA的两个输入的突触具有高度可塑性时，RA中的乙酰胆碱(ACh)含量和胆碱乙酰转移酶(ChAT)的酶活性一过性增加。为此，我们研究了毒鼠碱激动剂卡巴胆碱是否会影响磷脂酰肌醇(PI)在RA中的代谢。分别使用孵化后30d、50d的雄性斑雀和成鸟。在锂存在的情况下，通过测量[~3H]-肌醇标记的RA突触神经体中[~3H]-肌醇磷酸的积聚来检测卡巴胆碱刺激的PI转换。氨甲酰胆碱显著提高了磷脂周转率。氨甲酰胆碱刺激的PI周转率在孵化后50d达到最大值，然后下降到成虫水平。这些结果提示，在鸣唱学习过程中，ACh影响斑雀RA的突触可塑性，这是因为PI翻转激活了蛋白激酶C，使一些在突触可塑性中起重要作用的磷酸蛋白磷酸化。

A young male zebra finch learns its song during a sensitive period. The sensory motor phase of song learning is closely correlated to development of a song control nucleus, RA,which receives inputs from two other song control nuclei. We previously found that acetylcholine (ACh) content and the enzyme activity of choline acetyltransferase (ChAT) increase transiently in the RA during a sensitive period of song learning, when RA synapses for two inputs are highly plastic. For this purpose, we have investigated whether muscarinic agonist carbachol would affect phosphoinositide (PI) metabolism in the RA.The male zebra finch at 30 days, 50 days after hatching and adults were used. Carbachol-stimulated PI turnover was examined by measuring the accumulation of [3H]-inositol phosphates from [3H]-inositol labeled synaptoneurosomes of RA,in the presence of lithium. Carbachol increased PI turnover significantly. Carbachol-stimulated PI turnover reached a maximum at 50 days after hatching, and decreased to adult level. These results suggest that ACh affects synaptic plasticity of zebra finch RA during song learning, because PI turnover activate protein kinase C responsible for the phosphorylation of some phosphoproteins, which play a important role in synaptic plasticity.