Wang S S, Khiroug L, Augustine G J
Department of Neurobiology, Duke University Medical Center, Box 3209, Durham, NC 27710, USA.
Proc Natl Acad Sci U S A. 2000 Jul 18;97(15):8635-40. doi: 10.1073/pnas.130414597.
Localized, chemical two-photon photolysis of caged glutamate was used to map the changes in alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid-type glutamate receptors caused by long-term synaptic depression (LTD) in cerebellar Purkinje cells. LTD produced by pairing parallel fiber activity with depolarization was accompanied by a decline in the response of Purkinje cells to uncaged glutamate that accounted for both the time course and magnitude of LTD. This depression of glutamate responses was observed not only at the site of parallel fiber stimulation but also at more distant sites. The amount of LTD decreased with distance and was half-maximal 50 microm away from the site of parallel fiber activity. Estimation of the number of parallel fibers active during LTD induction indicates that LTD modified glutamate receptors not only at active synapses but also at 600 times as many inactive synapses on a single Purkinje cell. Therefore, both active and inactive parallel fiber synapses can undergo changes at a postsynaptic locus as a result of associative pre- and postsynaptic activity.
利用笼锁型谷氨酸的局部化学双光子光解来绘制小脑浦肯野细胞中由长期突触抑制（LTD）引起的α-氨基-3-羟基-5-甲基-4-异恶唑丙酸型谷氨酸受体的变化。通过将平行纤维活动与去极化配对产生的LTD伴随着浦肯野细胞对未笼锁型谷氨酸反应的下降，这解释了LTD的时间进程和幅度。谷氨酸反应的这种抑制不仅在平行纤维刺激部位观察到，在更远的部位也观察到。LTD的量随距离而减少，在距平行纤维活动部位50微米处达到最大值的一半。对LTD诱导期间活跃的平行纤维数量的估计表明，LTD不仅修饰了活跃突触处的谷氨酸受体，还修饰了单个浦肯野细胞上多达600倍的非活跃突触处的谷氨酸受体。因此，由于联合的突触前和突触后活动，活跃和非活跃的平行纤维突触都可以在突触后位点发生变化。
