Study on the regulatory mechanisms of transmitter release from presynaptic nerve boutons in CNS

据报道，一些哺乳动物CNS神经元共释放GABA和Gly，并且单个单一IPSC由GABA和Gly组成（Joneas等人）。此外，在突触后神经元中观察到的IPSC是由于GABA、Gly或GABA和Gly的联合作用。他们认为，单一IPSC和mIPSC子集的双重性质是由于GABA和Gly从单个脊髓中间神经元共同释放。奥布莱恩等人在mIPSC中发现了GABA和Gly向运动神经元的类似共传递，他还提出，GABA和Gly共同定位于同一突触前囊泡中，并从神经末梢共同释放。因此，我们调查，是否GABA和甘氨酸是共同释放从同一突触囊泡使用的“突触扣”制备大鼠脊髓神经元和“一个单一的扣局灶性刺激”技术，我们最近开发的。当从“突触终扣”制备物中记录到自发的微小突触后电流时，在2 mM [Ca^<2+>]_o下持续记录到GABA、Gly和混合mIPSC。有趣的是，在相对较低或较高的外部Ca浓度（分别为0.3- 7 mM）下，总是观察到GABA和Gly的共释放。当在单个终扣的共释放突触上施加0.2Hz的局灶性刺激时，可观察到GABA、Gly或它们的混合共释放三种不同的释放模式，表明GABA、Gly和GABA与Gty的组合分别储存在单个囊泡中并共同释放。

It was reported that some mammalian CNS neurons co-release GABA and Gly, and that a single unitary IPSC consists of GABA and Gly (Joneas et al.) Furthermore, IPSCs observed in the postsynaptic neurons were due to GABA, Gly, or combined action of GABA and Gly. They suggested that the dual nature of unitary IPSC and subset of mIPSCs are due to GABA and Gly co-released from a single spinal interneuron. Similar co-transmission of GABA and Gly to motoneurons was found in mIPSCs by O'brien et al., who also suggested that GABA and Gly are co-localized in the same presynaptic vesicle and are co-released from the nerve ending. We investigated, therefore, whether or not GABA and Gly are co-released from the same synaptic vesicle by use of 'synaptic bouton' preparation of rat spinal neurons and 'a single bouton focal stimulation' technique, which we recently developed. When spontaneous miniature postsynaptic currents were recorded from 'synaptic bouton' preparation, GABA, Gly, and mixed mIPSCs were constantly recorded at 2mM [Ca^<2+>]_o. Interestingly, the co-release of GABA and Gly was always observed ever at a relatively lower or higher external Ca concentration external Ca (0.3-7mM, respectively). When focal stimulation (0.2Hz) were applied in co-released synapse of a single bouton, three different pattern of release including GABA, Gly, or the mixed co-release of these transmitters were observed, indicating that GABA , Gly and GABA and Gty combination are separately stored in individual vesicles and are co-released.