Clendening B, Hume R I
Department of Biology, University of Michigan, Ann Arbor 48109.
J Neurosci. 1990 Dec;10(12):3977-91. doi: 10.1523/JNEUROSCI.10-12-03977.1990.
Neurons in the CNS generally receive inputs form multiple afferent sources. These afferent systems seldom all use the same neurotransmitter, so most central neurons are required to express multiple neurotransmitter receptors. This work addresses the issue of how multiple neurotransmitter receptors are regulated on the surface of individual neurons. We made whole-cell voltage-clamp recordings from identified chick sympathetic preganglionic neurons (SPNs) in dissociated cell cultures. The neurons were derived from stage 30-31 (7 d) chick embryos and were studied within the first week in vitro. We found that by 1 week in vitro, most SPNs responded to the application of GABA, glycine, and glutamate. The responses of SPNs to the amino acid neurotransmitters were similar to the responses of other CNS neurons to these 3 substances. SPNs became sensitive to these substances at different times in culture. At 1 d in vitro, most cells already responded to GABA, and about half of the cells also responded to glycine and kainate. In contrast, responses to NMDA and quisqualate were usually not seen until day 3-4 in vitro. Although there was a general trend for the amplitude of the responses of SPNs to each of the neurotransmitters to increase with time in vitro, there was an immense amount of cell-to-cell variability. By measuring the amplitudes of the responses of a series of SPNs to all 3 transmitters, we were able to test whether a common regulatory mechanism governed the level of responsiveness of SPNs to all 3 amino acid transmitters. We found no correlation between cells in the amplitudes of their responses to the 3 transmitters. Both the differences in time course of appearance of responsiveness and the lack of correlation in the amplitude of responses suggest that the multiple receptors on the surface of SPNs in vitro are independently regulated.
中枢神经系统中的神经元通常从多个传入源接收输入。这些传入系统很少都使用相同的神经递质，因此大多数中枢神经元需要表达多种神经递质受体。这项工作解决了单个神经元表面上多种神经递质受体如何被调节的问题。我们在解离细胞培养物中对已鉴定的鸡交感神经节前神经元（SPN）进行了全细胞电压钳记录。这些神经元来自30-31期（7天）的鸡胚胎，并在体外培养的第一周内进行研究。我们发现，到体外培养1周时，大多数SPN对γ-氨基丁酸（GABA）、甘氨酸和谷氨酸的应用有反应。SPN对氨基酸神经递质的反应与其他中枢神经系统神经元对这三种物质的反应相似。SPN在培养的不同时间对这些物质变得敏感。在体外培养1天时，大多数细胞已经对GABA有反应，约一半的细胞也对甘氨酸和海藻酸有反应。相比之下，对N-甲基-D-天冬氨酸（NMDA）和喹啉酸的反应通常直到体外培养第3-4天才出现。尽管SPN对每种神经递质的反应幅度总体上有随着体外培养时间增加的趋势，但细胞间存在极大的变异性。通过测量一系列SPN对所有三种递质的反应幅度，我们能够测试是否存在一种共同的调节机制来控制SPN对所有三种氨基酸递质的反应水平。我们发现细胞对这三种递质的反应幅度之间没有相关性。反应出现的时间进程差异以及反应幅度缺乏相关性都表明，体外培养的SPN表面上的多种受体是独立调节的。
