Staggered development of GABAergic and glycinergic transmission in the MNTB
Staggered development of GABAergic and glycinergic transmission in the MNTB
复制标题
DOI：
10.1152/jn.00798.2004
复制
发表时间：
2005-02-01
影响因子：
2.5
通讯作者：
Trussell, LO
中科院分区：
文献类型：
--
作者：
Awatramani, GB;Turecek, R;Trussell, LO
一些脑干和脊髓抑制系统的成熟的特征在于从GABA能传递转变为甘氨酸能传递。很少有人知道这种转变是如何表达的个别轴突输入和突触网站。我们在大鼠斜方体内侧核（MNTB）中探讨了这个问题。出生后5 - 7天（P5 - P7）的突触反应小，慢，主要由GABA（A）受体介导。到P8 - P12，出现了额外的、更快的甘氨酸能组分。在这些年龄，GABA A，甘氨酸，或两种类型的受体介导的传输，甚至在单一的突触网站。此后，甘氨酸能发育大大加速。到P25，诱发的抑制性突触后电流（IPSC）比在最年轻的组中测量的电流短10倍，大100倍，这表明激活快动力受体的突触输入的增殖。甘氨酸能微型IPSCs（mIPSCs）的大小和衰减率随着年龄的增长显着增加。GABA能mIPSC也加速，但幅度略有下降。总的来说，GABA能输入的功效显示P5和P20之间几乎没有成熟。虽然短杆菌肽穿孔膜片记录显示，GABA或甘氨酸去极化P5 - P7细胞，但超极化P14 - P15细胞，年轻的去极化输入不是阈上的。此外，抑制性轴突的囊泡释放特性也成熟了：未成熟大鼠的GABA能反应是高度异步的，而在老年大鼠中，精确的、阶段性的甘氨酸能IPSC即使在500 Hz刺激下也能传输。因此，抑制的发展的特点是协调修改的递质系统，囊泡释放动力学，氯梯度，受体的性质，和突触输入的数量。GABA/甘氨酸传递的明显转变主要是由于甘氨酸能功能增强。
Maturation of some brain stem and spinal inhibitory systems is characterized by a shift from GABAergic to glycinergic transmission. Little is known about how this transition is expressed in terms of individual axonal inputs and synaptic sites. We have explored this issue in the rat medial nucleus of the trapezoid body (MNTB). Synaptic responses at postnatal days 5 - 7 (P5 - P7) were small, slow, and primarily mediated by GABA(A) receptors. By P8 - P12, an additional, faster glycinergic component emerged. At these ages, GABA A, glycine, or both types of receptors mediated transmission, even at single synaptic sites. Thereafter, glycinergic development greatly accelerated. By P25, evoked inhibitory postsynaptic currents (IPSCs) were 10 times briefer and 100 times larger than those measured in the youngest group, suggesting a proliferation of synaptic inputs activating fast-kinetic receptors. Glycinergic miniature IPSCs (mIPSCs) increased markedly in size and decay rate with age. GABAergic mIPSCs also accelerated, but declined slightly in amplitude. Overall, the efficacy of GABAergic inputs showed little maturation between P5 and P20. Although gramicidin perforated-patch recordings revealed that GABA or glycine depolarized P5 - P7 cells but hyperpolarized P14 - P15 cells, the young depolarizing inputs were not suprathreshold. In addition, vesicle-release properties of inhibitory axons also matured: GABAergic responses in immature rats were highly asynchronous, while in older rats, precise, phasic glycinergic IPSCs could transmit even with 500-Hz stimuli. Thus development of inhibition is characterized by coordinated modifications to transmitter systems, vesicle release kinetics, Cl- gradients, receptor properties, and numbers of synaptic inputs. The apparent switch in GABA/glycine transmission was predominantly due to enhanced glycinergic function.