Analysis of Synaptic Transmission using Molecular Genetics

I)神经元突触缩短蛋白(n-syb)在突触传递中的作用。我们研究了缺乏n-syb的果蝇胚胎的突触传递。没有观察到神经诱发突触电流，但很容易检测到微小突触电流(MSCs)。骨髓间充质干细胞的频率依赖于钙离子。在无外源性钙离子的情况下，环磷酸腺苷不能增加间充质干细胞的频率。ii)由cAMP/PKA介导的两条独立通路促进果蝇神经肌肉接头自发释放递质。我们证明cAMP以n-syb依赖和非依赖的方式增强突触传递。iii)代谢性谷氨酸受体的激活增强了果蝇神经肌肉接头的突触传递。在无钙生理盐水中喷洒谷氨酸可增加自发性突触电流的频率。这一反应可被代谢性谷氨酸受体拮抗剂阻断。腺酰环化酶激活剂，如Forskolin，模拟谷氨酸…的作用更多的塔马特。谷氨酸的作用可被腺酰环化酶抑制剂阻断。在外源性钙离子存在的情况下，代谢型谷氨酸受体激动剂可增强突触传递。在果蝇幼虫神经肌肉接头处，末端释放的内源性谷氨酸通过涉及cAMP的过程增强突触传递。iv)突触缺陷的筛查揭示了一个参与果蝇胚胎突触前和突触后功能的基因座。分离到一个突触传递存在中度缺陷的新突变体。该基因被克隆并被发现与最近报道的基因apontic相同，apontic可能产生一种转录因子。v)在果蝇突触前末端发现了两个突触囊泡池。外/内循环池(容易释放的池)位于突触终末的外围，在低频刺激时维持突触传递，而在高频刺激时储备池中的小泡被释放。外/内循环池的大小与突触传递的量子含量成比例关系。vi)超微结构与神经肌肉接头的发育相关。在突触形成的早期，用电子显微镜观察神经肌肉接头的超微结构。较少

i) Role of neuronal synaptobrevin (n-syb) for synaptic transmission. We examined synaptic transmission in Drosophila embryos lacking n-syb. No nerve-evoked synaptic currents were observed, but miniature synaptic currents (mSCs) were readily detected. The frequency of mSCs was Ca^<2+> dependent. Cyclic AMP did not increase the frequency of mSCs in the absence of external Ca^<2+>.ii) Two independent pathways mediated by cAMP/PKA enhance spontaneous transmitter release at Drosophila neuromuscular junctions. We demonstrated that cAMP enhances synaptic transmission in the n-syb dependent and independent ways.iii) Activation of metabotropic glutamate receptors enhances synaptic transmission at the Drosophila neuromuscular junction. Puff application of glutamate in Ca^<2+> -free saline increased the frequency of spontaneous synaptic currents. This response was blocked by antagonists of metabotropic glutamate receptors. Adenylyl cyclase activators, such as forskolin, mimicked the effect of glu … More tamate. The effect of glutamate was blocked by an inhibitor of adenylyl cyclase. In the presence of external Ca^<2+>, an agonist of metabotropic glutamate receptors enhanced synaptic transmission. At the larval Drosophila neuromuscular junction endogeneous glutamate released at the terminal potentiates synaptic transmission via a process involving cAMP.iv) Screening for synaptic defects revealed a locus involved in presynaptic and postsynaptic functions in Drosophila embryos. A new mutant was isolated which has moderate defects in synaptic transmission. The gene was cloned and found to be identical to a recently reported gene, apontic, which presumably produces a transcription factor.v) Two synaptic vesicle pools were identified at the Drosophila presynaptic terminal. The exo/endo cycling pool (readily releasable pool) is in the periphery of synaptic terminals and maintains synaptic transmission during low frequency stimulation, while vesicles in the reserve pool are released during high frequency stimulation. The size of the exo/endo cycling pool is proportionately related to the quantal content of synaptic transmission.vi) Ultrastructure correlates of neuromuscular junction development. Ultrastructures of neuromuscular junction was examined in EM during early stages of synapse formation. Less