Durham D, Matschinsky F M, Rubel E W
Department of Otolaryngology/Head and Neck Surgery, University of Washington, Seattle 98195.
Hear Res. 1993 Nov;70(2):151-9. doi: 10.1016/0378-5955(93)90153-r.
The metabolism of second order auditory neurons in nucleus magnocellularis (NM) in the chick brainstem can be profoundly altered when excitatory input from the cochlea is removed. Within hours of cochlea removal, NM neurons show an increase in histochemical staining for the Kreb's cycle enzyme succinate dehydrogenase (SDH), followed in several days by decreases in SDH staining. We examined the activity of another Kreb's cycle enzyme, malate dehydrogenase (MDH) using a histochemical stain and a sensitive quantitative biochemical assay for comparison. We found changes in MDH staining similar in time course and magnitude to those of SDH; within 4 h of cochlea removal, MDH activity increases in ipsilateral NM neurons. By 9 days after cochlea removal MDH activity decreases, although not to the same degree as seen with SDH. Biochemical measurements of MDH activity also showed an early increase in activity in ipsilateral NM, followed at 9 days survival by a decrease in activity. Biochemical measurements of the activity of other enzymes in NM may be useful in further defining the metabolic consequences of deafferentation.
当来自耳蜗的兴奋性输入被去除时，雏鸡脑干大细胞神经核（NM）中二级听觉神经元的代谢会发生深刻改变。在去除耳蜗后的数小时内，NM神经元中参与三羧酸循环的酶琥珀酸脱氢酶（SDH）的组织化学染色增加，几天后SDH染色减少。我们使用组织化学染色和灵敏的定量生化测定法来检测另一种三羧酸循环酶苹果酸脱氢酶（MDH）的活性，以便进行比较。我们发现MDH染色的变化在时间进程和幅度上与SDH相似；在去除耳蜗后的4小时内，同侧NM神经元中的MDH活性增加。去除耳蜗9天后，MDH活性下降，尽管下降程度与SDH不同。MDH活性的生化测量也显示同侧NM中活性早期增加，在存活9天时活性下降。对NM中其他酶活性的生化测量可能有助于进一步明确去传入神经作用的代谢后果。
