■听力下降是与衰老过程相关的最普遍的单一感觉缺陷。提供令人信服的证据表明与传出听觉系统相关的保护作用,我们研究的目的是表征CBA/J小鼠在其寿命期内调节外毛细胞(OHC)活性的内侧橄榄耳蜗(MOC)传出突触数量与内毛细胞带状突触数量的年龄相关变化.
■将3个月大的CBA/J小鼠的Corti器官与10至20个月大的小鼠进行比较,以2个月为间隔分组。对于每一种动物,一只耳朵用于表征传出MOC纤维和外毛细胞(OHCs)之间的突触,而对侧耳用于分析内毛细胞(IHC)和螺旋神经节神经元(SGN)的I型传入神经纤维之间的带状突触。每个耳蜗在顶端被分开,中间,和基底转弯,分别。
■在14个月的基础耳蜗转中观察到IHC-SGN带状突触的首次显着的年龄相关下降,在16个月的中间转弯,和18个月大的顶端转弯。相比之下,CBA/J小鼠的传出MOC-OHC突触由于衰老而表现出不太明显的损失,仅在20个月大时在耳蜗的基底和中转中变得显着。
该研究说明了从20月龄开始的CBA/J小鼠中OHC的传出MOC神经支配的年龄相关减少。我们的发现表明,由于老化而引起的MOC-OHC突触的形态下降明显晚于IHC-SGN带状突触中观察到的下降。
UNASSIGNED: Hearing decline stands as the most prevalent single sensory deficit associated with the aging process. Giving compelling evidence suggesting a protective effect associated with the efferent auditory system, the goal of our study was to characterize the age-related changes in the number of efferent medial olivocochlear (MOC) synapses regulating outer hair cell (OHC) activity compared with the number of afferent inner hair cell ribbon synapses in CBA/J mice over their lifespan.
UNASSIGNED: Organs of Corti of 3-month-old CBA/J mice were compared with mice aged between 10 and 20 months, grouped at 2-month intervals. For each animal, one ear was used to characterize the synapses between the efferent MOC fibers and the outer hair cells (OHCs), while the contralateral ear was used to analyze the ribbon synapses between inner hair cells (IHCs) and type I afferent nerve fibers of spiral ganglion neurons (SGNs). Each cochlea was separated in apical, middle, and basal turns, respectively.
UNASSIGNED: The first significant age-related decline in afferent IHC-SGN ribbon synapses was observed in the basal cochlear turn at 14 months, the middle turn at 16 months, and the apical turn at 18 months of age. In contrast, efferent MOC-OHC synapses in CBA/J mice exhibited a less pronounced loss due to aging which only became significant in the basal and middle turns of the cochlea by 20 months of age.
UNASSIGNED: This study illustrates an age-related reduction on efferent MOC innervation of OHCs in CBA/J mice starting at 20 months of age. Our findings indicate that the morphological decline of efferent MOC-OHC synapses due to aging occurs notably later than the decline observed in afferent IHC-SGN ribbon synapses.