DIFFERENT PROPORTIONS OF N-METHYL-D-ASPARTATE AND NON-N-METHYL-D-ASPARTATE RECEPTOR CURRENTS AT THE MOSSY FIBER GRANULE CELL SYNAPSE OF DEVELOPING RAT CEREBELLUM
DIFFERENT PROPORTIONS OF N-METHYL-D-ASPARTATE AND NON-N-METHYL-D-ASPARTATE RECEPTOR CURRENTS AT THE MOSSY FIBER GRANULE CELL SYNAPSE OF DEVELOPING RAT CEREBELLUM
复制标题
DOI：
10.1016/0306-4522(93)90290-v
复制
发表时间：
1993-03-01
期刊：
影响因子：
3.3
通讯作者：
TAGLIETTI, V
中科院分区：
文献类型：
--
作者：
DANGELO, E;ROSSI, P;TAGLIETTI, V
苔藓状纤维颗粒细胞突触在出生后第二周和第三周经历了主要的发育变化。我们用原位颗粒细胞全细胞膜片钳记录的方法研究了出生后10-22天的突触传递。取大鼠小脑鞭旁脑片，胞外液中加入1.2 mM镁离子刺激苔藓纤维，诱发颗粒细胞兴奋性突触后电流。在出生后16-22天记录的大多数颗粒细胞中，兴奋电流的特征是先有一个快速的初始峰值，然后是一个较慢的成分，而在许多较不成熟的细胞中，几乎没有快速峰值。药理和动力学数据表明，快组分和慢组分分别由非N-甲基-D-天冬氨酸和N-甲基-D-天冬氨酸受体激活介导。非N-甲基-D-天冬氨酸电流的大小随着发育年龄的增加而增加，而NMDA电流的大小没有明显变化，非N-甲基-D-天冬氨酸电流随年龄的变化不能用记录条件或颗粒细胞电紧张性的变化来解释。此外，从出生后11天到16天，N-甲基-D-天冬氨酸受体上的镁离子阻断程度没有改变，不能解释非N-甲基-D-天冬氨酸/N-甲基-D-天冬氨酸电流比率的增加。因此，我们认为非N-甲基-D-天冬氨酸电流的年龄依赖性增加是不同年龄观察到不同突触后电流波形的主要原因。N-甲基-D-天冬氨酸和非N-甲基-D-天冬氨酸电流比例的发育变化可能与调节颗粒细胞成熟和兴奋性的过程有关。
The mossy fibre granule cell synapse undergoes major developmental changes during the second and third weeks after birth. We investigated synaptic transmission during postnatal days 10-22 by means of whole-cell patch-clamp recordings from granule cells in situ. Parasagittal slices were cut from rat cerebellar vermis, and excitatory postsynaptic currents were evoked in granule cells by mossy fibre stimulation with 1.2 mM Mg++ in the extracellular solution. In the majority of granule cells recorded at postnatal days 16-22, excitatory currents were characterized by a fast initial peak followed by a slower component, while in many of the cells recorded at more immature stages, the fast peak was virtually absent. Pharmacological and kinetic data indicated that the fast and slow components were mediated by non-N-methyl-D-aspartate and N-methyl-D-aspartate receptor activation, respectively. The magnitude of the non-N-methyl-D-aspartate current increased with developmental age, while the magnitude of the NMDA current did not change markedly.The age-dependent change of the non-N-methyl-D-aspartate currents could not be accounted for by changes in recording conditions or granule cell electrotonic properties. Furthermore, from postnatal day 11 to 16 the extent of Mg++ block on the N-methyl-D-aspartate receptor did not change, and could not explain the increasing non-N-methyl-D-aspartate/N-methyl-D-aspartate current ratio. We concluded therefore that the age-dependent increase of the non-N-methyl-D-aspartate cur-rent was the main cause of the different postsynaptic current waveforms observed at different ages. The developmental change in the proportion of N-methyl-D-aspartate and non-N-methyl-D-aspartate currents may be relevant to the processes regulating granule cell maturation and excitability.