Department of Neuroscience and Experimental Therapeutics, Albany Medical College, Albany, NY 12208, USA.
VA West Los Angeles Medical Center, VAGLAHS, West Los Angeles, CA 90073, USA.
Respir Physiol Neurobiol. 2024 Mar;321:104206. doi: 10.1016/j.resp.2023.104206. Epub 2023 Dec 21.
The state-dependent noradrenergic activation of hypoglossal motoneurons plays an important role in the maintenance of upper airway patency and pathophysiology of obstructive sleep apnea (OSA). Chronic intermittent hypoxia (CIH), a major pathogenic factor of OSA, contributes to the risk for developing neurodegenerative disorders in OSA patients. Using anterograde tracer, channelrhodopsin-2, we mapped axonal projections from noradrenergic A7 and SubCoeruleus neurons to hypoglossal nucleus in DBH-cre mice and assessed the effect of CIH on these projections. We found that CIH significantly reduced the number of axonal projections from SubCoeruleus neurons to both dorsal (by 68%) and to ventral (by73%) subregions of the hypoglossal motor nucleus compared to sham-treated animals. The animals' body weight was also negatively affected by CIH. Both effects, the decrease in axonal projections and body weight, were more pronounced in male than female mice, which was likely caused by less sensitivity of female mice to CIH as compared to males. The A7 neurons appeared to have limited projections to the hypoglossal nucleus. Our findings suggest that CIH-induced reduction of noradrenergic innervation of hypoglossal motoneurons may exacerbate progression of OSA, especially in men.
舌下神经运动神经元的去甲肾上腺素能状态依赖性激活在维持上气道通畅和阻塞性睡眠呼吸暂停(OSA)的病理生理学中起着重要作用。慢性间歇性低氧(CIH)是 OSA 的主要致病因素,它增加了 OSA 患者发生神经退行性疾病的风险。我们使用顺行示踪剂、通道视紫红质-2,在 DBH-cre 小鼠中绘制了去甲肾上腺素能 A7 和 SubCoeruleus 神经元到舌下神经核的轴突投射,并评估了 CIH 对这些投射的影响。我们发现,与假处理动物相比,CIH 显著减少了 SubCoeruleus 神经元到舌下运动核背侧(减少 68%)和腹侧(减少 73%)亚区的轴突投射数量。动物的体重也受到 CIH 的负面影响。与雌性小鼠相比,雄性小鼠的轴突投射减少和体重下降的影响更为明显,这可能是由于雌性小鼠对 CIH 的敏感性低于雄性小鼠所致。A7 神经元似乎对舌下神经核的投射有限。我们的研究结果表明,CIH 诱导的舌下运动神经元去甲肾上腺素能传入减少可能会加重 OSA 的进展,尤其是在男性中。