Instituto de Neurociencias, Universidad Miguel Hernández-Consejo Superior de Investigaciones Científicas, 03550 San Juan de Alicante, Spain.
Instituto de Investigación Biomédica y Sanitaria de Alicante, 03010 Alicante, Spain.
Int J Mol Sci. 2023 Aug 9;24(16):12620. doi: 10.3390/ijms241612620.
The role of TRPA1 in the thermosensitivity of the corneal cold thermoreceptor nerve endings was studied in young and aged mice. The contribution of the TRPA1-dependent activity to basal tearing and thermally-evoked blink was also explored. The corneal cold thermoreceptors' activity was recorded extracellularly in young (5-month-old) and aged (18-month-old) C57BL/6WT (WT) and TRPA1 knockout (TRPA1-KO) mice at basal temperature (34 °C) and during cooling (15 °C) and heating (45 °C) ramps. The blink response to cold and heat stimulation of the ocular surface and the basal tearing rate were also measured in young animals using orbicularis oculi muscle electromyography (OOemg) and phenol red threads, respectively. The background activity at 34 °C and the cooling- and heating-evoked responses of the cold thermoreceptors were similar in WT and TRPA1-KO animals, no matter the age. Similar to the aged WT mice, in the young and aged TRPA1-KO mice, most of the cold thermoreceptors presented low frequency background activity, a low cooling threshold, and a sluggish response to heating. The amplitude and duration of the OOemg signals correlated with the magnitude of the induced thermal change in the WT but not in the TRPA1-KO mice. The basal tearing was similar in the TRPA1-KO and WT mice. The electrophysiological data suggest that the TRPA1-dependent nerve activity, which declines with age, contributes to detecting the warming of the ocular surface and also to integrating the thermally-evoked reflex blink.
研究了瞬时受体电位通道 A1（TRPA1）在角膜冷感受器神经末梢热敏性中的作用，分别在年轻和老年小鼠中进行。还探讨了 TRPA1 依赖性活动对基础流泪和热诱发眨眼的贡献。在基础温度（34°C）下以及在冷却（15°C）和加热（45°C）斜坡期间，分别在年轻（5 月龄）和老年（18 月龄）C57BL/6WT（WT）和 TRPA1 敲除（TRPA1-KO）小鼠中，通过细胞外记录角膜冷感受器的活动。还使用眼轮匝肌肌电图（OOemg）和酚红线分别测量年轻动物对眼部表面冷和热刺激的眨眼反应以及基础流泪率。在 WT 和 TRPA1-KO 动物中，无论年龄大小，在 34°C 时的背景活动以及冷感受器的冷却和加热诱发反应均相似。与老年 WT 小鼠一样，在年轻和老年 TRPA1-KO 小鼠中，大多数冷感受器具有低频背景活动、较低的冷却阈值以及对加热的反应迟缓。OOemg 信号的幅度和持续时间与 WT 小鼠中诱导的热变化幅度相关，但与 TRPA1-KO 小鼠中不相关。TRPA1-KO 和 WT 小鼠的基础流泪率相似。电生理数据表明，随着年龄的增长而下降的 TRPA1 依赖性神经活动有助于检测眼部表面的变暖，并且有助于整合热诱发的反射性眨眼。
