Land P W, Akhtar N D
Department of Neurobiology, University of Pittsburgh School of Medicine, PA 15261, USA.
Somatosens Mot Res. 1999;16(2):139-50. doi: 10.1080/08990229970573.
Chelatable zinc is co-localized with glutamate in the synaptic vesicles of a distinct population of telencephalic neurons. The present study used a histochemical technique to localize zinc-containing terminals within the somatosensory barrel cortex (S1) of normal adult rats and rats that had been subjected to 4-6 weeks of tactile deprivation produced by simple whisker trimming beginning either at birth or during adulthood. In normal adult rats intense staining for synaptic zinc was observed in laminae I, II/III and V. Lamina VI was moderately stained, particularly within sublamina VIa where thalamic axons terminate. Thalamorecipient barrel centers in lamina IV were distinguished by the relative absence of synaptic zinc and were bounded by darkly stained inter-barrel septa. This pattern was unchanged in rats whose whiskers were trimmed only during adulthood, suggesting that synaptic zinc constitutes a relatively stable pool that is resistant to subtle changes in sensory input. By contrast, neonatal whisker trimming resulted in a marked increase in density of synaptic zinc specifically within the centers of deprived barrels in lamina IV. This redistribution of synaptic zinc appears to be permanent since altered staining of deprived barrels persists after extended periods of tactile experience with regrown whiskers. The results in normal rats indicate that zinc-containing circuits are distributed heterogeneously within S1 where they most likely subserve intracortical vs thalamocortical processing. The altered distribution of zinc-ergic circuits following neonatal whisker trimming suggests that zinc-sequestering neurons in developing S1 are particularly sensitive to early tactile experience.
可螯合锌与谷氨酸在端脑神经元的一个独特群体的突触小泡中共定位。本研究使用组织化学技术，在正常成年大鼠以及从出生时或成年期开始经简单剪须造成4 - 6周触觉剥夺的大鼠的体感桶状皮层（S1）内定位含锌终末。在正常成年大鼠中，在I层、II/III层和V层观察到突触锌的强烈染色。VI层染色适中，特别是在丘脑轴突终末所在的VIa亚层内。IV层中的丘脑接受性桶状中心以相对缺乏突触锌为特征，并由深色染色的桶间隔界定。在仅在成年期剪须的大鼠中，这种模式没有改变，这表明突触锌构成了一个相对稳定的池，对感觉输入的细微变化具有抗性。相比之下，新生大鼠剪须导致IV层中被剥夺桶状中心内突触锌密度显著增加。这种突触锌的重新分布似乎是永久性的，因为在胡须重新生长并经过长时间触觉体验后，被剥夺桶状中心的染色改变仍然持续。正常大鼠的结果表明，含锌回路在S1内异质分布，在那里它们最有可能参与皮层内与丘脑皮层的处理。新生大鼠剪须后锌能回路分布的改变表明，发育中的S1中螯合锌的神经元对早期触觉体验特别敏感。
