The tongue is a muscular hydrostat, with lingual movements occurring during breathing, chewing, swallowing, vocalization, vomiting, coughing and grooming/sexual activities. In the elderly, reduced lingual dysfunction and weakness contribute to increased risks of obstructive sleep apnea and aspiration pneumonia. In Fischer 344 (F344) rats, a validated model of aging, hypoglossal motor neuron death is apparent, although there is no information regarding tongue strength. The intrinsic tongue muscles, the superior and inferior longitudinal, transversalis and verticalis exist in an interdigitated state. Recently, we established a method to measure the specific force of individual intrinsic tongue muscle, accounting for the tissue bulk that is not in the direction of uniaxial force. In the longitudinal muscles of 6- (n = 10), 18- (n = 9) and 24-month-old (n = 12) female and male F344 rats, we assessed specific force, fatigability, fiber type dependent cross-sectional area (CSA) and overall CSA. Muscle force and fatigue was assessed ex vivo using platinum plate simulation electrodes. Tongue muscles were frozen in melting isopentane, and transverse sections cut at 10 µm. Muscle fiber type was classified based on immunoreactivity to myosin heavy chain (MyHC) isoform antibodies. In H&E stained muscle, CSA and uniaxial muscle contributions to total tongue bulk was assessed. We observed a robust ∼30% loss of longitudinal specific force, with reductions in overall longitudinal muscle fiber CSA and specific atrophy of type IIx/IIb fibers. It will be important to investigate the mechanistic underpinnings of hypoglossal motor neuron death and tongue muscle weakness to eventually provide therapies for age-associated lingual dysfunctions.

舌头是肌肉的流体调节器，在呼吸、咀嚼、吞咽、发声、呕吐、咳嗽和梳理毛发/性活动时会发生舌运动。在老年人中，舌功能障碍和无力的减少会导致阻塞性睡眠呼吸暂停和吸入性肺炎的风险增加。在 Fischer 344 (F344) 大鼠中，尽管没有关于舌头力量的信息，但经过验证的衰老、舌下运动神经元死亡模型是显而易见的。舌固有肌、上、下纵肌、横肌、纵肌呈叉指状态存在。最近，我们建立了一种测量个体固有舌肌比力的方法，考虑了非单轴力方向的组织体积。在 6 月龄（ n  = 10）、18 月龄（n  = 9）和 24 月龄（n  = 12）雌性和雄性 F344 大鼠的纵向肌肉中，我们评估了比力、疲劳性、纤维类型依赖性横截面面积 (CSA) 和总体 CSA。使用铂板模拟电极离体评估肌肉力量和疲劳。将舌肌冷冻在融化的异戊烷中，并切成 10 µm 的横切片。肌纤维类型根据肌球蛋白重链 (MyHC) 亚型抗体的免疫反应性进行分类。在 H&E 染色的肌肉中，评估了 CSA 和单轴肌肉对总舌头体积的贡献。我们观察到纵向比力显着损失约 30%，总体纵向肌纤维 CSA 减少，IIx/IIb 型纤维特异性萎缩。研究舌下运动神经元死亡和舌肌无力的机制基础对于最终为与年龄相关的舌功能障碍提供治疗方法非常重要。