Rea M A, Ferriera S, Randolph W, Glass J D
Circadian Neurobiology Research Group, Armstrong Laboratory, Brooks AFB, Texas 78235.
Proc Soc Exp Biol Med. 1993 Oct;204(1):104-9. doi: 10.3181/00379727-204-43641.
Daily profiles of the extracellular concentrations of glutamate (GLU), aspartate, and glutamine in the region of the suprachiasmatic nuclei (SCN) of the Djungarian hamster were examined by in vivo microdialysis. Hamsters with a dialysis probe located in or near the SCN exhibited a diurnal variation in the extracellular concentration of GLU. Glutamate levels rose gradually during the latter half of the subjective day and through the night to reach peak levels near the time of lights-on. The extracellular concentration of GLU was significantly elevated (P < 0.05) during the latter half of the dark phase relative to the level at midday. The average peak in extracellular GLU was 217% of the midday value (P < 0.05; n = 5). Diurnal fluctuations were not consistently observed in the concentrations of aspartate in SCN dialysates. The nocturnal rise in extracellular GLU in the SCN was not attenuated by perfusion with 10 microM tetrodotoxin, although this concentration of tetrodotoxin completely blocked increases in extracellular GLU caused by simultaneous perfusion with 30 microM veratridine. Collectively, these results point to a diurnal rhythm in extracellular concentration of GLU in the SCN region which may not reflect diurnal variations in synaptic activity.
通过体内微透析法检测了长爪沙鼠视交叉上核（SCN）区域谷氨酸（GLU）、天冬氨酸和谷氨酰胺细胞外浓度的每日变化情况。透析探针位于SCN内或其附近的沙鼠，其GLU细胞外浓度呈现出昼夜变化。在主观日的后半段以及整个夜间，谷氨酸水平逐渐上升，在开灯时间附近达到峰值。相对于中午水平，在黑暗期后半段，GLU的细胞外浓度显著升高（P < 0.05）。细胞外GLU的平均峰值是中午值的217%（P < 0.05；n = 5）。在SCN透析液中天冬氨酸浓度未观察到一致的昼夜波动。尽管10微摩尔的河豚毒素完全阻断了同时灌注30微摩尔藜芦碱所引起的细胞外GLU的增加，但用10微摩尔河豚毒素灌注并未减弱SCN中细胞外GLU的夜间升高。总体而言，这些结果表明SCN区域细胞外GLU浓度存在昼夜节律，这可能并不反映突触活动中的昼夜变化。
