The brainstem nucleus hypoglossus contains motoneurons that provide the exclusive motor nerve supply to the tongue. In addition to voluntary tongue movements, tongue muscles rhythmically contract during a wide range of physiological activities, such as respiration, swallowing, chewing and sucking. Hypoglossal motoneurons are destroyed early in amyotrophic lateral sclerosis (ALS), a fatal neurodegenerative disease often associated with a deficit in the transport system of the neurotransmitter glutamate.The present study shows how periodic electrical discharges of motoneurons are mainly produced by a neuronal network that drives them into bursting mode via glutamatergic excitatory synapses. Burst activity is, however, modulated by the intrinsic properties of motoneurons that collectively synchronize their discharges via gap junctions to create ‘group bursters’. When glial uptake of glutamate is blocked, a distinct form of pathological bursting spontaneously emerges and leads to motoneuron death. Conversely, H2O2-induced oxidative stress strongly increases motoneuron excitability without eliciting bursting. Riluzole (the only drug currently licensed for the treatment of ALS) suppresses bursting of hypoglossal motoneurons caused by blockage of glutamate uptake and limits motoneuron death. These findings highlight how different patterns of electrical oscillations of brainstem motoneurons underpin not only certain physiological activities, but also motoneuron death induced by glutamate transporter impairment.
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机译：脑干核下垂含有运动神经元，其向舌头提供唯一的运动神经供应。除了自愿的舌头运动外，舌头肌肉在广泛的生理活动（如呼吸，吞咽，咀嚼和吮吸）中有节律地收缩。舌下运动神经元在肌萎缩性侧索硬化（ALS）早期被破坏，肌萎缩性侧索硬化（ALS）是致命性神经退行性疾病，通常与神经递质谷氨酸的转运系统缺陷有关。它们通过谷氨酸能兴奋性突触进入爆发模式。但是，爆发活动受到运动神经元的固有属性的调节，该活动神经元通过间隙连接共同使放电同步，从而形成“群爆发”。当神经胶质对谷氨酸的摄取被阻止时，自然会出现不同形式的病理性破裂并导致运动神经元死亡。相反，H 2 O 2诱导的氧化应激强烈增加了运动神经元的兴奋性，而不会引起爆裂。利鲁唑（目前唯一可用于治疗ALS的药物）可抑制由谷氨酸摄取受阻引起的舌下运动神经元爆发，并限制运动神经元死亡。这些发现突显了脑干运动神经元的不同电振荡模式不仅支持某些生理活动，而且还支持谷氨酸转运蛋白损伤引起的运动神经元死亡。
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