Zinc functions in the central nervous system

脑屏障系统，即血脑屏障和血脑脊液屏障，对脑内锌的稳态起着重要的作用。锌通过这两个屏障被提供给大脑。锌在神经元和神经胶质细胞中以锌金属蛋白的形式存在。大脑中大约10%的锌存在于突触小泡中，可能是离子锌，在突触神经传递中可能是一种内源性神经调节剂。大脑中存在含锌神经元，这是谷氨酸能神经元的一个亚类，它将锌隔离在突触前小泡中，并以钙和脉冲依赖的方式释放锌，特别是在边缘系统，如海马体和杏仁核。膳食缺锌会影响脑内锌的稳态。富含锌的囊泡区域，即海马体，对饮食缺锌有反应，这会导致学习障碍和嗅觉障碍。大鼠学习障碍可通过补锌饮食恢复。嗅觉识别也被杏仁核神经元终末释放的锌的螯合作用可逆地干扰。此外，癫痫小鼠的癫痫发作影响了大脑中锌的动态平衡。锌缺乏也增加了癫痫发作的敏感性，这可能会降低水泡性锌。因此，脑内锌的动态平衡与脑功能密切相关。囊泡锌可能通过谷氨酸参与兴奋性神经传递的调节。即使是成年动物，甚至可能是成年人类，充足的锌供应对大脑功能和神经疾病的预防也很重要。

The brain barrier system, i.e., the blood-brain and blood-cerebrospinal fluid barriers, is important for zinc homeostasis in the brain. Zinc was supplied to the brain via both the barriers. A large portion of zinc serves as zinc metalloproteins in neurons and glial cells. Approximately 10% of the total zinc in the brain, probably ionic zinc, exists in the synaptic vesicles, and may serve as an endogenous neuromodulator in synaptic neurotransmission. The presence of zinc-containing neurons, a subclass of glutamatergic neurons, that sequester zinc in the presynaptic vesicles and release it in a calcium-and impulse-dependent manner has been demonstrated in the brain, especially in the limbic system such as hippocampus and amygdala. Dietary zinc deprivation affected zinc homeostasis in the brain. Vesicular zinc-enriched regions, i.e., the hippocampus, was responsive to dietary zinc deprivation, which caused learning impairment and olfactory dysfunction. The learning impairment was recovered by feeding with zinc-adequate diet. Olfactory recognition was also reversibly disturbed by the chelation of zinc released from amygdalar neuron terminals. Moreover, zinc homeostasis in the brain was affected by seizure in El (epilepsy) mice. The susceptibility to epileptic seizure, which may decrease vesicular zinc, was also enhanced by zinc deficiency. Therefore, zinc homeostasis in the brain is closely related to brain functions. Vesicular zinc may be involved in regulation of excitatory neurotransmission via glutamate. Even in adult animals and probably adult humans, adequate zinc supply is important for brain functions and prevention of neurological diseases.