Elias S A, Yae H, Ebner T J
Department of Neurosurgery, University of Minnesota, Minneapolis 55455.
Neuroscience. 1993 Feb;52(4):771-86. doi: 10.1016/0306-4522(93)90528-n.
Using optical imaging, the effects of excitatory amino acids and their antagonists on the spatial pattern of activity evoked by the stimulation of parallel fibers in the cerebellar cortex of the anesthetized rat were examined. A vermal folium was stained with the stryrl voltage-sensitive dye RH-795 and imaged with a cooled charge-coupled service system during the activation of the parallel fibers with surface stimulation. Stimulation of the cerebellar cortex produced discrete "beams" of optical activity consistent with extracellular field recordings. The signal-to-noise ratio was excellent (> 10:1), reducing the number of stimuli, exposure time, and acquisition time needed to produce images. Extracellular field potential recordings were used to assay neuronal activity as well as the effects of the various excitatory amino acid agonists. Application of several glutamate receptor antagonists reversibly blocked the optical signals as well as the synaptic components of the extracellular field potentials. Neither N-methyl-D-aspartate nor its antagonist, (+/-)-2-amino-7-phosphonoheptanoic acid, had any affect on the optical signals or field potentials. These results indicate that the optical signal is not due to the evoked parallel fiber activity, but is generated mainly by postsynaptic targets and the parallel fiber synaptic action is primarily mediated by non-N-methyl-D-aspartate receptors. Other excitatory amino acid agonists had a differential effect on the optical response. Glutamate and kainate increased the "on beam" optical signal evoked by parallel fiber stimulation, in amplitude and width. In contrast, quisqualate always decreased the amplitude and width of the optical beam. Also, quisqualate produced an increase in fluorescence lateral to the optical beam, possibly due to an increase in "off beam" inhibitory activity. The changes in the extracellular field potentials were in agreement with the effects on the optical signals. Two possible mechanisms are proposed to account for the inhibitory effect of quisqualate. One is that quisqualate desensitizes Purkinje cell receptors, the other is that inhibitory interneurons in the cerebellar cortex are more preferentially excited with quisqualate application which in turn inhibits Purkinje cells both "on beam" and "off beam". In conclusion, voltage-sensitive dye optical signals evoked by stimulation of the cerebellar surface were imaged at high signal-to-noise levels using a cooled charge-coupled device system. Use of excitatory amino acid agonists and antagonists demonstrated that the optical signal was dependent on postsynaptic activity and confirmed that the parallel fiber postsynaptic action is primarily mediated by non-N-methyl-D-aspartate receptors.(ABSTRACT TRUNCATED AT 400 WORDS)
利用光学成像技术，研究了兴奋性氨基酸及其拮抗剂对麻醉大鼠小脑皮质平行纤维刺激所诱发的活动空间模式的影响。在表面刺激激活平行纤维的过程中，用苯乙烯基电压敏感染料RH - 795对蚓部小叶进行染色，并通过冷却电荷耦合服务系统进行成像。小脑皮质刺激产生离散的光学活动“束”，与细胞外场记录一致。信噪比极佳（>10:1），减少了生成图像所需的刺激次数、曝光时间和采集时间。细胞外场电位记录用于测定神经元活动以及各种兴奋性氨基酸激动剂的作用。几种谷氨酸受体拮抗剂的应用可逆地阻断了光学信号以及细胞外场电位的突触成分。N - 甲基 - D - 天冬氨酸及其拮抗剂（±）-2 - 氨基 - 7 - 磷酸庚酸对光学信号或场电位均无影响。这些结果表明，光学信号并非由诱发的平行纤维活动所致，而是主要由突触后靶点产生，且平行纤维的突触作用主要由非N - 甲基 - D - 天冬氨酸受体介导。其他兴奋性氨基酸激动剂对光学反应有不同影响。谷氨酸和海人酸增加了平行纤维刺激诱发的“束上”光学信号的幅度和宽度。相反，quisqualate总是降低光束的幅度和宽度。此外，quisqualate使光束侧面的荧光增加，这可能是由于“束外”抑制活动增加所致。细胞外场电位的变化与对光学信号的影响一致。提出了两种可能的机制来解释quisqualate的抑制作用。一种是quisqualate使浦肯野细胞受体脱敏，另一种是小脑皮质中的抑制性中间神经元在应用quisqualate时更优先被兴奋，进而抑制“束上”和“束外”的浦肯野细胞。总之，使用冷却电荷耦合器件系统在高信噪比水平下对小脑表面刺激诱发的电压敏感染料光学信号进行了成像。兴奋性氨基酸激动剂和拮抗剂的使用表明光学信号依赖于突触后活动，并证实平行纤维的突触作用主要由非N - 甲基 - D - 天冬氨酸受体介导。（摘要截短至400字）
