Analysis of Synaptic Transmission using Molecular Genetics

i)神经元突触短暂蛋白（n-syb）在突触传递中的作用。我们研究了缺乏n-syb的果蝇胚胎中的突触传递。未观察到神经诱发的突触电流，但容易检测到微型突触电流（mSCs）。mSCs的频率依赖于Ca^<2+>。在没有外部Ca^<2+>的情况下，环状AMP没有增加mSCs的频率。ii) cAMP/PKA介导的两条独立通路增强果蝇神经肌肉连接处的自发递质释放。我们证明了cAMP以依赖n-syb和独立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点的突触传递。谷氨酸在Ca^<2+>游离生理盐水中喷施可增加自发突触电流的频率。这种反应被代谢性谷氨酸受体拮抗剂阻断。腺苷酸环化酶激活剂，如福斯克林，模仿了谷氨酸的作用。谷氨酸的作用被腺苷酸环化酶抑制剂阻断。在外部Ca^<2+>存在的情况下，代谢性谷氨酸受体的激动剂增强了突触传递。在果蝇幼虫的神经肌肉连接处，末端释放的内源性谷氨酸通过一个涉及cAMP的过程增强了突触传递。iv)对突触缺陷的筛选揭示了果蝇胚胎中参与突触前和突触后功能的一个位点。分离到一个新的突变体，其突触传递具有中等缺陷。该基因被克隆，并发现与最近报道的基因apontic相同，apontic可能产生转录因子。v)在果蝇突触前末端鉴定出两个突触囊泡池。外/内循环池（易释放池）位于突触末端外围，在低频刺激时维持突触传递，而储备池中的囊泡在高频刺激时被释放。外/内循环池的大小与突触传递的量子内容成正比。神经肌肉连接处发育的超微结构相关因素。在神经突触形成早期，用电镜观察神经肌肉连接处的超微结构。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