Foran L, Kupelian C, Laroia S, Esper J, Kulesza R J
Department of Anatomy, Lake Erie College of Osteopathic Medicine, Erie, PA,, United States.
Folia Morphol (Warsz). 2017;76(4):582-589. doi: 10.5603/FM.a2017.0052. Epub 2017 Jun 14.
Glutamate is the most abundant excitatory neurotransmitter in the central nervous system, and is stored and released by both neurons and astrocytes. Despite the important role of glutamate as a neurotransmitter, high levels of extracellular glutamate can result in excitotoxicity and apoptosis. Monosodium glutamate (MSG) is a naturally occurring sodium salt of glutamic acid that is used as a flavour enhancer in many processed foods. Neonatal exposure to MSG has been shown to result in neurodegeneration in several forebrain regions, characterised by neuronal loss and neuroendocrine abnormalities. However, the brainstem effects of neonatal MSG exposure have not been investigated. It is therefore hypothesized that MSG exposure during the early postnatal period would impact brainstem lower motor neurons involved in feeding behaviour. The effect of neonatal MSG exposure on brainstem lower motor neurons was investigated by exposing rat pups to either 4 mg/g MSG or saline from postnatal day (P) 4 through 10. On P28, brains were preserved by vascular perfusion with fixative, frozen sectioned and stained for Nïssl substance. The number, size and shape of brainstem motor neurons were compared between MSG and saline-exposed animals. MSG exposure had no impact on the total number of neurons in the nuclei examined. However, MSG exposure was associated with a significant increase in the number of round somata in both the trigeminal and facial nuclei. Furthermore, MSG exposure resulted in significantly smaller neurons in all motor nuclei examined. These results suggest that neonatal exposure to MSG impacts the development of brainstem lower motor neurons which may impact feeding and swallowing behaviours in young animals.
谷氨酸是中枢神经系统中含量最丰富的兴奋性神经递质，由神经元和星形胶质细胞储存并释放。尽管谷氨酸作为神经递质发挥着重要作用，但细胞外谷氨酸水平过高会导致兴奋性毒性和细胞凋亡。味精（MSG）是谷氨酸的天然钠盐，在许多加工食品中用作增味剂。已表明新生儿接触味精会导致几个前脑区域发生神经退行性变，其特征为神经元丢失和神经内分泌异常。然而，新生儿接触味精对脑干的影响尚未得到研究。因此，有人提出假说，出生后早期接触味精会影响参与进食行为的脑干下运动神经元。通过从出生后第4天（P4）至第10天给幼鼠喂食4mg/g味精或生理盐水，研究了新生儿接触味精对脑干下运动神经元的影响。在P28时，通过用固定剂进行血管灌注来保存大脑，进行冷冻切片并对尼氏物质进行染色。比较了接触味精和生理盐水的动物之间脑干运动神经元的数量、大小和形状。接触味精对所检查核团中的神经元总数没有影响。然而，接触味精与三叉神经核和面神经核中圆形胞体数量的显著增加有关。此外，接触味精导致所有检查的运动核团中的神经元明显变小。这些结果表明，新生儿接触味精会影响脑干下运动神经元的发育，这可能会影响幼小动物的进食和吞咽行为。
